Cometography: Volume 6, 1983–1993: A Catalog of Comets [6] 9780521872164, 0521872162

Table of contents :
Contents
Introduction
Acknowledgments
Cometography: A Catalog of Comets
Appendix 1: Uncertain objects
Appendix 2: Periodical and book abbreviations
Person index
Comet designation index

Citation preview

Cometography A Catalog of Comets Volume 6: 1983–1993

Cometography is a multi-volume catalog of every comet observed from ancient times up to the 1990s, when the internet took off as a medium of scientific record. It uses the most reliable orbits known to determine the distances from the Earth and Sun at the time of discovery and last observation, as well as the largest and smallest angular distance to the Sun, most northerly and southerly declination, closest distance to the Earth, and other details, to enable the reader to understand each comet’s physical appearance. Volume 6, the final volume in the catalog, covers the observations and pertinent calculations for every comet seen between 1983 and 1993. The comets are listed in chronological order, with complete references to publications relating to each comet and physical descriptions of each comet’s development throughout its apparition. Cometography is the definitive reference on comets through the ages, for astronomers and historians of science. Ga r y Kr o n k has held a life-long passion for astronomy, and has been researching historical information on comets ever since sighting Comet Kohoutek in 1973/74. His work has been published in numerous magazines, and in two previous books: Comets: A Descriptive Catalog (1984) and Meteor Showers: A Descriptive Catalog (1988). Kronk holds positions in various astronomical societies, including Coordinator of the Comet Section of the Association of Lunar and Planetary Observers, and Consultant for the American Meteor Society. The International Astronomical Union named minor planet 48300 Kronk, in honor of the extensive research Gary Kronk has done in cometography. Ma i k Me y e r has observed comets since 1987. Besides comet observing, he is researching cometary orbits in order to link and identify historic comet apparitions. His speciality area is the history of comet hunting. In 2002, he discovered the Meyer group of sunskirting comets. Meyer was leader of the Comet Section of the German Vereinigung der Sternfreunde and served as assistant editor of the International Comet Quarterly (ICQ). The International Astronomical Union named minor planet 52005 Maik, in honor of his research work in comets. Dav i d Se a r g e n t studied and tutored philosophy at the University of Newcastle, NSW, Australia; he has also written books and articles covering a variety of subjects. He has been an amateur astronomer since his early teens, with comets being his principal interest. Seargent directed the Australian Comet Section from early 1980s until early 2000s and acted as visual co-ordinator for Australia of International Halley Watch 1985/6. He is the discoverer of C/1978 T1 (Seargent).

Cometography A Catalog of Comets volume 6: 1983–1993

Gary W. Kronk, Maik Meyer, and David A. J. Seargent

University Printing House, Cambridge CB2 8BS, United Kingdom One Liberty Plaza, 20th Floor, New York, NY 10006, USA 477 Williamstown Road, Port Melbourne, VIC 3207, Australia 4843/24, 2nd Floor, Ansari Road, Daryaganj, Delhi - 110002, India 79 Anson Road, #06-04/06, Singapore 079906 Cambridge University Press is part of the University of Cambridge. It furthers the University’s mission by disseminating knowledge in the pursuit of education, learning and research at the highest international levels of excellence. www.cambridge.org Information on this title: www.cambridge.org/9780521872164 © Gary W. Kronk, Maik Meyer, and David A. J. Seargent 2017 This publication is in copyright. Subject to statutory exception and to the provisions of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published 2017 Printed in the United Kingdom by Clays, St Ives plc A catalogue record for this publication is available from the British Library Library of Congress Cataloging in Publication data Kronk, Gary W. Cometography / a catalog of comets / Gary W. Kronk. p. cm. ISBN 978-0-521-87216-4 1. Comets – Catalogs. I. Title QB722.K75 1999 523.6 – dc21

98-38683 CIP

ISBN 978-0-521-87216-4 Hardback Cambridge University Press has no responsibility for the persistence or accuracy of URLs for external or third-party internet websites referred to in this publication, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate.

Contents

vii

Introduction

xii

Acknowledgments

1

Cometography: A Catalog of Comets

824

Appendix 1: Uncertain objects

827

Appendix 2: Periodical and book abbreviations

828

Person index

843

Comet designation index

v

Introduction

The period of 1983 through 1993 brought forth many improvements in the study of comets, including larger telescopes and an increasing use of digital photography. These led to more discoveries and longer periods of visibility than in the past.

Comet discoveries The period covered by this volume marks the last hurrah of visual amateur comet hunters, as a result of the use of new technology in the last years of the twentieth century. Of the 167 new comet discoveries (including five rediscoveries of lost comets), amateurs were involved in 54 of these (32%). If one looks at the credited discoveries, i.e. comets named for a discoverer that can include up to three discoverers per comet, 132 were photographic discoveries and 59 were visual discoveries (31%). Photographic amateur discoveries amounted to 13 (7%). This shows that visual comet hunting was still dominant among amateur comet hunters during this time. The USA leads with 89 discoveries, followed by Japan with 30 and Australia with 27. There were 21 discoveries made by the following satellites: the Infrared Astronomical Satellite (IRAS), SOLWIND, and the Solar Maximum Mission (SMM). Of the observatory surveys, the major share of discoveries was grabbed by the Schmidt telescopes at Palomar Observatory (California, USA) and Siding Spring Observatory (New South Wales, Australia). Looking at the individuals who discovered comets from 1983 through 1993, it can be seen that D. H. Levy found almost all of his credited comets (visual and photographic from Palomar) during this period (21). Also, C. S. and E. M. Shoemaker found all of their 32 comets during this time. Other successful professional astronomers were E. F. Helin (11), J. E. Mueller (10), R. H. McNaught (9), M. Hartley (9), and K. S. Russell (9). The most successful amateurs were (besides Levy) D. E. Machholz (8), W. A. Bradfield (5) and H. J. Brewington (4). The latter half of the 1990s saw the advent of the large professional Charged Coupled Device (CCD) surveys (e.g. LINEAR, CSS, Spacewatch, etc.), which led to a significant drop in amateur comet discoveries. In recent times, amateurs have become quite successful in discovering comets by using CCD cameras.

Comet observations Several very active comet observers mentioned in Cometography volume 5 continued to observe during most, if not all, of the period covered by this vii

introduction

present volume. The most notable include A. F. A. L. Jones, J. E. Bortle, T. Seki, and C. S. Morris. The most notable observers to make their first impression during the years covered by this volume were J. V. Scotti, A. Hale, R. J. Bouma, and A. Nakamura. Scotti and Nakamura particularly stood out. Although the major goal of their work was to precisely measure the positions of comets, they were frequently the first person to recover periodic comets, the only people to provide physical descriptions when a comet was too faint for amateur astronomers, and made the final observation of numerous comets. Although visual observations remained the most abundant type of observation, film photography was falling out of favor, being replaced by digital cameras using the Charged Coupled Device (CCD). The CCD could digitally capture the light from celestial objects and a computer could then combine these images to uncover fainter objects and fainter detail. In just a matter of a few minutes, amateur astronomers could capture images showing objects as faint as magnitude 20, which equaled what observatories could accomplish with larger telescopes and exposure times of an hour or more from the 1950s into the 1980s. The methods of determining a comet’s magnitude changed little since the last volume of Cometography. The most preferred was the “Sidgwick method,” which began with the observer memorizing both the size and brightness of a comet. He/she then defocused the stars until their disks were the same diameter as the in-focus comet. At that point, the magnitudes of these star disks were compared to the memorized brightness of the in-focus comet.

Astronomical periodicals For the period covered by this volume, the most dominant publication providing comet observations and analysis was the International Comet Quarterly. It had become the clearing house for comet observations. The Central Bureau for Astronomical Telegrams remained the official clearing house for comet discoveries and recoveries. It continued to disseminate this information through the International Astronomical Union Circular at irregular intervals. The Minor Planet Center began incorporating precise positions of comets in the Minor Planet Circulars in the late 1970s. Observer notes, which provided descriptive information of comets, would sometimes be included. Something new appeared in the final years covered by this volume: the World Wide Web (WWW). The very first websites dealing with astronomy were created in 1992 and 1993, including G. W. Kronk’s Cometography website, which would provide observations and digital images of comets, both past and present. viii

introduction

The most interesting comets from 1983 to 1993 Because of the shorter period of time covered by this volume, there were no spectacular comets; however, four comets did become fairly easy naked-eye targets, while two others became memorable for other reasons. Comet C/1983 H1 (IRAS–Araki–Alcock) was discovered in late April of 1983 and is the brightest comet listed in this volume. It brightened rapidly as it approached both the Sun and Earth. The comet made the fourth closest approach of a comet to Earth (0.0312 AU) on May 11, at which time the magnitude was about 2, while the coma was 2–3 across. In addition, the comet traveled just over 44 across the sky in 24 hours. Its rapid movement across the starry background could not only be detected through a telescope in a matter of minutes, but such motion could even be observed with the naked eye. This comet was a naked-eye object from May 6 to May 18. Comet C/1989 W1 (Aarseth–Brewington) became the brightest comet since 1983, ultimately becoming visible to the naked eye from December 18 to December 29. It reached a maximum magnitude of about 3 and its visual tail length exceeded 2. Comet C/1989 X1 (Austin) was discovered about three weeks after C/1989 W1. Hopes were raised that it would become a bright comet when initial calculations of its orbit indicated that it could reach magnitude 2 in 1990 April. Although it did become a naked eye object from April 21 to June 4, it barely reached a peak magnitude of 4. When closest to Earth on 1990 May 25, experienced observers reported a coma 1 across and a tail extending at least 2. Comet C/1990 K1 (Levy) was discovered while comet C/1989 X1 was at its brightest. It was visible to the naked eye from July 23 to September 20, reaching a maximum brightness of about 3.5. Experienced observers reported a maximum coma diameter of nearly 1 and a tail length of between 3 and 5. Comet 109P/1992 S2 (Swift–Tuttle) barely reached naked-eye visibility, but was of interest to astronomers ever sense it was identified as the parent of August’s Perseid meteor shower in the nineteenth century. Although its appearance in 1992–1993 was that of a fine binocular object, large telescopes revealed fine structure within the coma, including hoods, fountains, and jets. But the most notable aspect of this comet’s apparition was that activity levels of the Perseid meteor shower increased. The normal Zenithal Hourly Rate (ZHR) for the Perseids is about 120 meteors. As the comet moved through the inner solar system, the ZHR rose to 350 in 1991, 220 in 1992, 300 in 1993, and 250 in 1994. Comet D/1993 F2 (Shoemaker–Levy 9) never became particularly bright, with only a handful of visual observations ever being reported. But it did become newsworthy. When the comet was discovered in 1993, it had a very unusual appearance, being referred to as a “squashed comet” and a “string of pearls.” It turned out that the comet had been torn apart during an ix

introduction

extremely close approach to Jupiter in 1992 and all of the pieces were on a collision course with that planet. When the comet pieces hit Jupiter over several days in July 1994, the event was covered by newspapers around the world and even made the front covers of the magazines Time and Newsweek.

Cometography Perhaps the biggest change to this volume is one that was never seen by the reader. When Cometography was originally proposed to Cambridge University Press back in 1995, the series was planned to end with 1999. Work had then barely started on this last volume and we did not begin working on it full time until after the publication of volume 5 in 2010. By that time, the Solar and Heliospheric Observatory (SOHO) had discovered 2000 comets since it went into operation in 1996, nearly 300 of which were during 1996–1999. In addition, systematic surveys by other observatories resulted in increasing the number of comets found each year. Where the period of 1990–1995 saw an average of 12 comet discoveries per year, there were 44 discoveries in 1996 (most of which were from SOHO) and then 104 discoveries in 1997, 140 in 1998, and 135 in 1999. These numbers do not include the normal returns of periodic comets. Needless to say, the final volume of Cometography was becoming far bigger than we had imagined two decades ago. So, it was decided to end the series with the comets of 1993. As it turns out, this volume is still one of the largest of the Cometography series. As with volume 5, the biggest change in volume 6 is the condensing of well-observed comets. We have continued to concentrate on presenting the observations of experienced observers, but we also began presenting the observations of the most prolific observers. The reason for adding the latter was to present a better picture of how some individual observers saw changes in the course of a month. As can be imagined, this in itself presented challenges, as it seems some inexperienced observers reported all observations regardless of atmospheric conditions. This sometimes led to wild variations in the magnitude and coma diameter that they reported, while experienced observers reported few such variations. So, we used our own judgment by looking at all reported observations for each month and using those two, three, or four observers who provided the best picture of a comet’s appearance. We chose to leave out the term “total magnitude” in this volume. Every reference to “magnitude” is the observer’s “total magnitude” estimate. It should be noted that even though some observers occasionally provide “nuclear magnitude” estimates, it is highly likely that this is not the magnitude of the true nucleus, but of the much larger nuclear condensation, meaning the nucleus and bright material emanating from it. Exceptions would be the nuclear magnitude estimates reported by observers who specifically image comets that are very far away from the Sun and show little or no emissions. x

introduction

It should also be noted that the positions given in this volume are representative of those initially reported by the people making the discoveries/recoveries and final observations, but have been converted to equinox 2000.0.

Brian G. Marsden A long-time inspiration to the three authors of this volume was Brian G. Marsden, who passed away in 2010. Each of us has our own stories as to how Brian encouraged us in our observing, research, and writing that span several decades. No other astronomer of the modern era has shown more of a willingness to listen to amateur astronomers, answer their letters and e-mail, give constructive help, and encourage them like Brian did. In fact, the Cometography books became a reality because of Brian. Not only did he encourage G. W. Kronk to do this project, but also approached Cambridge University Press in 1995 and suggested they contact Kronk about publishing this series. He will be missed.

xi

Acknowledgments

The authors would like to express our gratitude to those individuals who contributed their time in answering questions, checking plate logs and observing notes, and/or sending us papers about their research. They played important roles in helping us finish this sixth and final volume of Cometography. These authorities include the following (in alphabetical order): Reinder J. Bouma (Netherlands) Gernot Burkhardt (Astronomisches Rechen-Institut, Heidelberg, Germany) Paul Camilleri (Australia) Kazimieras Cernis (Lithuania) Maurice L. Clark (Australia) Anita L. Cochran (McDonald Observatory, Texas, USA) Alan C. Gilmore (Mt. John University Observatory, Lake Tekapo, New Zealand) Alan Hale (Las Cruces, New Mexico, USA) Jean-Louis Heudier (Caussols, France) Pamela M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) Don E. Machholz (California, USA) Lucie Maquet (L’institut de mécanique céleste et de calcul des éphémérides, France) Robert H. McNaught (Siding Spring Observatory, New South Wales, Australia) Karen J. Meech (Mauna Kea, Hawaii, USA) Jean E. Mueller (Palomar Observatory, California, USA) Akimasa Nakamura (Kuma Kogen Astronomical Observatory, Japan) Andrew R. Pearce (Australia) Patrick Rocher (L’institut de mécanique céleste et de calcul des éphémérides, France) James V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) Jonathan Shanklin (England) Brian A. Skiff (Lowell Observatory, Arizona, USA) Giovanni Sostero (Remanzacco Observatory, Italy) Reiner Stoss (Germany) Ulrich Thiele (Calar Alto Observatory, Spain) Jana Tichá (Klet Observatory, Czech Republic) Special thanks go to Syuichi Nakano, who promptly answered every question we have ever sent to him and even calculated some new orbits at the request of Maik Meyer and Gary W. Kronk! David Seargent would like to thank his wife, Meg, for her encouragement and support during the preparation of his contributions to this volume. xii

acknowledgments

Maik Meyer especially likes to thank his family. His wife, Sara, and his three boys, Joris, Tilmann, and Hauke, provided him with the time to work on the book but also reminded him that there are other important things in life. Gary Kronk wants to thank his wife, Kathy, who never stops encouraging him in everything he does. His sons, David and Michael, and his daughter-in-law, Jennifer, continue to be blessings in his life.

xiii

Cometography: A Catalog of Comets

7P/Pons– Recovered: 1983 January 12.51 (Δ = 1.90 AU, r = 1.60 AU, Elong. = 58
) Winnecke Last seen: 1983 October 6.65 (Δ = 1.46 AU, r = 2.33 AU, Elong. = 141
) Closest to the Earth: 1983 August 6 (1.2315 AU) 1983 IV=1983b Calculated path: SER (Rec), OPH (Jan. 20), SER (Feb. 21), SCT (Feb. 26), AQL (Mar. 8), SGR (Mar. 12), CAP (Mar. 25), AQR (Apr. 2), CAP (Apr. 10), AQR (Apr. 23), CET (May 29), FOR (Aug. 4), SCL (Sep. 9) Two predictions were published for the return of this comet. J. V. Carey (1981) applied planetary perturbations to the predicted orbit for the 1976 apparition. The integration revealed a perihelion date of 1983 April 7.51. S. Nakano (1982) took 43 positions from the period spanning 1951 to 1976, included planetary perturbations, and solved for nongravitational effects. He predicted the next perihelion date would occur on April 7.50. E. Everhart (Chamberlin Observatory field station, Bailey, Colorado, USA) and T. Seki (Geisei, Kochi, Japan) independently recovered this comet. Everhart photographed the comet with a 41-cm reflector on 1983 January 12.51 and gave the position as α = 15h 51.3m, δ = 1
590 (2000). He noted the comet’s appearance was definite, but extremely faint, with a magnitude of 19. Seki first photographed the comet on January 14.85 using a 60-cm reflector. He described it as diffuse, with condensation, and also estimated the magnitude as 19. Confirming observations were obtained on January 19.50 by Everhart and January 20.84 by Seki, at which time the magnitude was given as 19 and 18.5, respectively. A. C. Gilmore (Mt. John University Observatory, Lake Tekapo, New Zealand) photographed the comet on April 16 and May 22, but no descriptive information was provided. Following an alert by R. J. Bouma suggesting that the comet may be brighter than predicted, A. R. Pearce and M. L. Clark (Western Australia, Australia) made several visual observations during May and June. Using a 41-cm reflector, Pearce gave the magnitude as 12.3 and the coma diameter as 1.20 on May 16. He saw the comet again on May 19, 20, and 24 with the aid of a 15-cm reflector, estimating magnitudes of 11.9–12.0 and coma diameters of 0.9–1.00 . Clark first observed the comet on May 16, using his 41-cm reflector, judging the magnitude as 12.3 and the coma diameter as 1.20 . Clark gave the magnitude as 12.1 on May 19 and 12.6 on June 9, noting the coma diameter as 20 and 1.50 , respectively. 1

cometography: a catalog of comets

While visiting T. A. Cragg (Siding Spring Observatory New South Wales, Australia), A. Hale observed the comet through a 32-cm reflector on June 15. He estimated the magnitude as 12.6 and gave a very approximate estimate of the coma diameter as about 1–20 , indicating that it was diffuse and slightly condensed. The final visual observation was by Hale (California, USA) who marginally detected the comet through his 20-cm reflector on June 22, but because of the comet’s low elevation and a rapidly brightening sky, no formal magnitude estimate was made. Everhart photographed the comet on September 5. It then reached a maximum elongation of 142
on September 30 and attained its most southerly declination of 33
on October 3. The comet was last detected on October 6.61 and October 6.65, when astronomers at Siding Spring Observatory imaged it using the 122-cm Schmidt telescope. They gave the magnitude as 19. The position on the last date was given as α = 1h 12.7m, δ = 32
580 (2000). Multiple apparition orbits have been calculated by T. Kobayashi (1989), S. Nakano (1993, 1999, 2005), and B. G. Marsden (2005). All of these calculations applied full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of April 7.51 and a period of 6.36 years. The nongravitational terms were within the following ranges: A1 = 0.00 to +0.05 and A2 = +0.0021 to +0.0034. The orbit of Nakano (2005) is given below. T ω Ω (2000.0) i q e 1983 Apr. 7.5079 (TT) 172.3365 93.4307 22.3070 1.253985 0.634716

absolute magnitude: H10 = 9.88 (Bortle, from visual estimates by Pearce, Clark, and Hale) full moon: 1982 Dec. 15, 1983 Jan. 28, Feb. 27, Mar. 28, Apr. 27, May 26, Jun. 25, Jul. 24, Aug. 23, Sep. 22, Oct. 21 sources: J. V. Carey, BAA Handbook for 1982 (1981 Aug.), p. 79; S. Nakano, Nakano Note, No. 414 (1982 Apr. 5); E. Everhart and T. Seki, IAUC, No. 3765 (1983 Jan. 24); M. L. Clark, ICQ, 5 (1983 Jul.), p. 68; A. C. Gilmore and E. Everhart, MPC, No. 8088 (1983 Sep. 22); A. R. Pearce and M. L. Clark, ICQ, 5 (1983 Oct.), p. 95; J. Bortle, ST, 66 (1983 Nov.), p. 473; A. C. Gilmore, MPC, No. 8219 (1983 Nov. 20); T. Kobayashi, CCO, 6th ed. (1989), pp. 30, 63, 69; S. Nakano, Nakano Note, No. 588 (1993 Apr. 7); S. Nakano, Nakano Note, No. 695 (1999 Oct. 31); B. G. Marsden, CCO, 16th ed. (2005), pp. 100–1; S. Nakano, Nakano Note, No. 1207 (2005 Jul. 20); A. Hale correspondence with D. A. J. Seargent (2014). 140P/1983 C1 Prediscovery: 1983 February 8.65 (Δ = 0.99 AU, r = 1.98 AU, Elong. = 176
) (Bowell–Skiff) Discovered: 1983 February 11.28 (Δ = 0.99 AU, r = 1.97 AU, Elong. = 175
) Last seen: 1983 June 10.22 (Δ = 1.94 AU, r = 2.14 AU, Elong. = 86
) 2

cometography: a catalog of comets

1983 II=1983c Closest to the Earth: 1983 February 16 (0.9835 AU) Calculated path: LEO (Pre), CNC (Feb. 28), LEO (Mar. 17), SEX (May 28), LEO (Jun. 3) E. L. G. Bowell (Lowell Observatory, Arizona, USA) discovered this comet on exposures obtained by B. A. Skiff (Lowell Observatory, Anderson Mesa Station, Arizona, USA) using the 33-cm photographic telescope on 1983 February 11.28 and February 15.26. For the first date, the position was given as α = 9h 28.6m, δ = +18
240 (2000). The magnitude was given as 16.2 and 16.5, respectively, and the comet was described as diffuse, with slight condensation, but exhibiting no tail. C. S. Shoemaker and E. M. Shoemaker (Palomar Observatory, California, USA) located the comet on a photographic plate exposed using the 46-cm Schmidt telescope on February 15.26. A prediscovery image was found on a plate exposed on February 8.65 by S.-L. Wei (Purple Mountain Observatory, China). The comet was at a maximum elongation of 176
on the 8th. Several observations were made during the remainder of February. R. E. McCrosky and G. Schwartz (Oak Ridge Observatory, Massachusetts, USA) obtained a 27-minute exposure on the 16th, using the 155-cm reflector, and estimated the nuclear magnitude as 18. E. S. Barker (McDonald Observatory, Texas, USA) acquired a photograph using the 272-cm reflector on the 17th and estimated the magnitude as 18. He noted that the spectrum revealed a weak emission of cyanogen. That same night, T. Seki (Geisei, Kochi, Japan) gave the magnitude as 17 and described the comet as diffuse, with condensation. On the 19th, Skiff gave the magnitude as 16.5. On the 20th, A. C. Gilmore and P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) estimated the magnitude as 17. Seki gave the photographic magnitude as 16.5 on the 21st. Four photographic magnitude estimates were reported in March. A. Mrkos and Z. Vávrová (Klet Observatory, Czech Republic) gave the magnitude as 16.5 on the 4th. Skiff gave the magnitude as 16.8 on the 9th and 17.0 on the 17th. On the 18th, Seki estimated the magnitude as 18. Only two observatories managed to photograph the comet from April onward: Oak Ridge Observatory and Chamberlin Observatory field station (Bailey, Colorado, USA). At Oak Ridge Observatory, Schwartz used the 155-cm reflector to photograph the comet on April 12, June 6, and June 9. At Chamberlin, E. Everhart photographed the comet with the 41-cm reflector on May 16 and estimated the magnitude as 19. The comet was last detected on June 10.22, when Everhart photographed it using the 41-cm reflector. The position was α = 11h 03.5m, δ = +3
570 (2000). The first published orbit was by B. G. Marsden on 1983 February 22. He took 13 positions obtained during the period spanning February 11–20 and calculated an elliptical orbit with a perihelion date of 1983 March 15.11 and 3

cometography: a catalog of comets

a period of 15.2 years. Marsden acknowledged that the short-period nature had been confirmed by similar orbits by Bowell and T. Urata, but noted that the period was “still somewhat uncertain.” The elliptical orbit was confirmed on March 28, when Marsden used 16 positions from the period spanning February 11 to March 9. The resulting perihelion date was March 15.33, while the period was 15.66 years. After the final observations of this comet were obtained, both Marsden and S. Nakano independently calculated orbits using most of the available positions and included perturbations by Mercury to Pluto. The result was a perihelion date of March 15.17 and a period of 15.67 years. Multiple apparition orbits have been calculated by Nakano (1999), P. Rocher (2000), K. Kinoshita (2001), and T. Kobayashi (2012). All of these calculations used positions from the 1983 and 1999 apparitions and applied full planetary perturbations. The result was a perihelion date of March 15.19–15.21 and a period of 15.70–15.71. Interestingly, despite only two apparitions being available, Rocher did determine nongravitational terms, which were given as A1 = +8.36 and A2 = +7.4596. Kinoshita’s orbit is given below. T ω Ω (2000.0) i q e 1983 Mar. 15.1961 (TT) 169.0041 346.3051 3.7989 1.945100 0.689962

absolute magnitude: H10 = 13.8 (Kronk) full moon: 1983 Jan. 28, Feb. 27, Mar. 28, Apr. 27, May 26, Jun. 25 sources: R. E. McCrosky and G. Schwartz, HOPL (1983); E. L. G. Bowell and B. A. Skiff, IAUC, No. 3773 (1983 Feb. 16); R. E. McCrosky, G. Schwartz, E. S. Barker, T. Seki, B. A. Skiff, A. C. Gilmore, P. M. Kilmartin, and B. G. Marsden, IAUC, No. 3775 (1983 Feb. 22); E. L. G. Bowell, B. A. Skiff, R. E. McCrosky, G. Schwartz, T. Seki, A. C. Gilmore, P. M. Kilmartin, and B. G. Marsden, MPC, Nos. 7727–8, 7773 (1983 Mar. 28); C. S. Shoemaker, E. M. Shoemaker, T. Seki, A. Mrkos, Z. Vávrová, and B. A. Skiff, MPC, No. 7796 (1983 Apr. 27); T. Seki and E. Everhart, MPC, No. 7878 (1983 May 26); E. Everhart, MPC, No. 7997 (1983 Jun. 25); B. G. Marsden, MPC, No. 8052 (1983 Jul. 24); S. Nakano, Nakano Note, No. 435 (1983 Sep. 11); S.-L. Wei, MPC, No. 9602 (1985 May 4); G. V. Williams, IAUC, No. 7076 (1998 Dec. 28); S. Nakano, CCO, 13th ed. (1999), pp. 82–3; P. Rocher correspondence with G. W. Kronk (2000); K. Kinoshita correspondence with G. W. Kronk (2001); T. Kobayashi, Nakano Note, No. 2313 (2012 Jul. 30). C/1983 H1 Prediscovery: 1983 April 17.05 (Δ = 0.60 AU, r = 1.15 AU, Elong. = 88
) (IRAS–Araki– Discovered: 1983 April 25.85 (Δ = 0.39 AU, r = 1.08 AU, Elong. = 90
) Alcock) Last seen: 1983 October 4.64 (Δ = 2.06 AU, r = 2.31 AU, Elong. = 91
) Closest to the Earth: 1983 May 11 (0.0312 AU) 1983 VII=1983d Calculated path: LYR (Pre), CYG (Apr. 21), DRA (Apr. 24), UMi (May 9), DRA–UMa (May 10), LYN–CNC (May 11), HYA (May 12), PUP (May 13), CAR (Aug. 12), PIC (Sep. 11), DOR (Sep. 28) 4

cometography: a catalog of comets

This comet made one of the closest known approaches to Earth, but in an era of easy international communications, the confusion surrounding its discovery was reminiscent of the old days. The Infrared Astronomical Satellite (IRAS) was launched from Vandenberg Air Force Base (California, USA) on 1983 January 25. Its purpose was to provide the most complete picture of the sky in the infrared wavelength, a wavelength that can only be poorly observed from Earth’s surface. Since it was expected that IRAS could be in an ideal position to detect fast-moving minor planets, the IRAS Preliminary Analysis Facility was established at the University of Leicester (England). Using special software, the images would be analyzed shortly after being received from IRAS to try and find moving objects. J. Davies and S. F. Green (University of Leicester), as well as B. Stewart (Rutherford Appleton Laboratory, England), were examining IRAS images on 1983 April 26, when they recognized a moving object on images obtained on April 25.85 and April 25.93, which represented two consecutive orbits. The object was thought to be a fast-moving minor planet and from the first image, Davies gave the position as α = 19h 07.6m, δ = +48
430 (2000). The Leicester group had formed a worldwide network of observatories to help in the confirmation of fast-moving objects, and telegrams were soon dispatched. T. Oja (Kvistaberg, Sweden) provided the first confirmation, but his three photographs obtained during April 27.89 to April 27.94 revealed a comet instead of a minor planet. The diameter of the nucleus was 15–2000 . The initial request for observations sent out by the Leicester group did not include a message to the Central Bureau for Astronomical Telegrams (CBAT), the clearinghouse for comet information. CBAT did, however, know of the discovery through other sources. First, H. Rickman (Uppsala Observatory, Sweden) had left an unclear message on the bureau’s answering machine, which did not give positions. Second, a conversation between B. G. Marsden (CBAT) and J. B. Gibson (Palomar Observatory, California, USA) took place on May 2, and the latter astronomer told Marsden that, at the request of a secondhand source, he had exposed several plates in the region of the supposed minor planet found by IRAS, but had not yet developed the plates. Meanwhile, G. E. D. Alcock (Peterborough, England), a previous discoverer of four comets and four novae, had decided to conduct his routine nova search from inside his home on May 3. He was sweeping with 15  80 binoculars, through a closed window, when he located a large, diffuse object in Draco on May 3.92. Alcock quickly alerted several British amateur astronomers, one of whom was G. S. Keitch, who, in turn, telephoned C. S. Morris (Cambridge, Massachusetts, USA). Morris then alerted CBAT. Shortly thereafter, on May 3.96, G. M. Hurst (Wellingborough, England), another British amateur alerted by Alcock, reported that he had confirmed 5

cometography: a catalog of comets

the comet and determined its magnitude as 6.2. He added that the coma was 120 across. CBAT now had two comet reports: Alcock’s comet situated in Draco, and the IRAS object, for which they had no idea of its position in the sky. Marsden suspected these were the same. His suspicion was based on the facts that Alcock’s comet was situated about 90
from the Sun and IRAS was restricted to only observing objects 90
from the Sun. Marsden telephoned Gibson, knowing he must have had positions to search for the “minor planet,” and found out that the plates of May 2.46 and May 2.49 had revealed a comet. Gibson said the six-minute and four-minute exposures revealed trails, which exhibited a strongly condensed nucleus and a faint asymmetric coma about 20 across. The coma was denser on the northeast side, but no tail was visible. The discovery saga did not end with Gibson’s confirmation. While Marsden was trying to contact Davies to acquire the discovery observations, word came from Tokyo Observatory that G. Araki (Yuzawa, Niigata, Japan) had discovered a comet on May 3.61. He estimated the comet’s magnitude as 7. Prediscovery images were later found. T. Kumamori (Muro, Nara, Japan) found the comet on a photograph exposed on April 20.70, while the comet was found by H. Huth, P. Kroll, and G. A. Richter (Sonneberg Observatory, Germany) near the plate limit of two simultaneous exposures obtained on April 17.05. They estimated the magnitude as 12. Several experienced observers provided observations on May 4, with the magnitude given as 5.9 by Morris, 6.0 by D. W. E. Green (Cambridge, Massachusetts, USA), and 6.3 by J.-C. Merlin (Le Creusot, France). Morris was observing with a 4-cm refractor and noted the coma was 150 across and fan-shaped toward PA 55
. He noted, “nonstellar condensation near focus of parabolic hood.” Green observed with 20  80 binoculars and said the coma was 180 across. Merlin used 7  50 binoculars for the magnitude estimate. Switching to his 15-cm reflector, he said the coma was slightly condensed and 140 across, while a tail extended 150 in PA 100
. Observations during the next few days revealed a rapid brightening, as well as a rapid growth of the coma, as the comet approached both the Earth and Sun. The comet reached a maximum elongation of 93
on May 5, at which time J. E. Bortle (Stormville, New York, USA) gave the magnitude as 6.1, using his 20  80 binoculars. Most observers were noting a slightly condensed coma 150 to 210 across. Bortle reported a “column structure” in PA 90
. V. Smith (McDonald Observatory, Texas, USA) visually observed the comet using the 272-cm reflector and noted a stellar nucleus, but no other structure within the coma; however, Smith also examined the spectrum of the comet and noted some faint diatomic carbon emission from a “very faint extension 5 [arc seconds] to the northeast.” The magnitude estimates on the 6th ranged from 5.2 to 5.9, with the average near 5.6. Most observers had reported little change in the coma, as estimates of its 6

cometography: a catalog of comets

diameter ranged from 160 to 200 and it was moderately condensed. Green (Oak Ridge Observatory, Cambridge, Massachusetts, USA) became the first observer to see the comet with the naked eye on May 6.27. On May 7, observers were reporting magnitudes ranging from 4.5 to 6.3, with the average near 5.0. Naked-eye observations were becoming more numerous. Observers with small binoculars or no optical aid were reporting coma diameters between 200 and 530 . A 15-minute exposure with a 205-mm telephoto lens and Kodak VR1000 film was obtained by M. W. Buie (Sonoita, Arizona, USA), which indicated a diameter of about 300 . The comet seemed to have undergone rather drastic changes by May 8. The coma diameter was being estimated as 180 to 860 across, depending on the transparency of the atmosphere at various observers’ locations. Subsequently, the magnitude estimates also varied considerably and ranged from 2.5 to 5.9, with the average near 4.4. Naked-eye magnitude estimates by Bortle, Green, and Keitch revealed values of 4.6, 4.4, and 3.7, respectively. Keitch also noted that his 20  80 binoculars revealed two tails: one extending 0.33
in PA 167
and the other extending 0.80
in PA 329
. The large number of naked-eye observations on the 9th revealed the coma diameter was 400 to 1260 . Magnitude estimates ranged from 1.9 to 5.1, with an average near 3.4. Estimates of the coma’s level of condensation became almost useless as descriptions ranged from very little to very strong condensation. Buie obtained a 30-minute exposure of the comet using a 14-cm Schmidt camera and 2415 Kodak film. This revealed a tail >3
long, which extended off the edge of the frame. The comet attained its most northerly declination of +74
on May 10. Naked-eye estimates of the magnitude ranged from 1.9 to 3.5, with an average near 2.8. Naked-eye estimates of the coma diameter ranged from 900 to 1680 , with an average near 1300 . Merlin said his 7  50 binoculars revealed a tail extending 1
in PA 286
. The comet was closest to Earth on May 11. Its rapid motion took it out of Ursa Major, through Lynx, and almost halfway across Cancer, amounting to a distance of just over 44
in 24 hours. Naked-eye estimates of the magnitude ranged from 1.6 to 4.4, with an average near 2.4. Naked-eye estimates of the coma diameter ranged from 500 to 2100 , with an average near 1220 . C. E. Spratt (British Columbia, Canada) said his 20-cm reflector revealed a tail extending 0.25
in PA 270
, while Keitch said his 30-cm reflector revealed a tail extending 0.07
in PA 253
. J. R. Johnson and S. M. Larson (Catalina Station, Mt. Bigelow, Arizona, USA) directly observed the comet using the 154-cm reflector at powers up to 1000. They noted the nuclear condensation was magnitude 10.5. They also reported that direct images of the inner coma “show a sunward-directed fan indicative of a slowly-rotating nucleus. . . and a faint extension [protruding] 300 km in the antisolar direction.” The comet was apparently at its best on May 12. Naked-eye estimates of the magnitude ranged from 1.5 to 3.8, with an average near 2.2. Naked-eye 7

cometography: a catalog of comets

estimates of the coma diameter ranged from 72’ to 240’, with an average of 1560 . Using 7  50 binoculars, Bortle noted tail extensions of 2.5
in PA 250
and 3
in PA 230
. B. Magaw (Brewster, New York, USA) photographed the comet and noted a coma just over 1
in diameter. R. Nolthenius (Lockwood Valley, California, USA) observed the nuclear region of this comet occult the star SAO 98040 on May 12.19, using a 20-cm reflector and a power of 275. He noted that the condensation was “not quite resolved, distinctly fuzzy, [and] ~1.3 mag fainter than the star.” The occultation “lasted 0.8 [second] (corresponding to 31 km at the comet’s distance), during which the combined image slowly faded by 0.5 mag, then brightened, with no obvious interval of constant light.” The comet showed definite signs of fading on May 13, with a significant drop in the number of naked-eye observations. Bortle estimated the magnitude as 3.1 and noted an uncondensed coma 60’ across. R. J. Bouma was visiting D. A. J. Seargent (The Entrance, New South Wales, Australia) and gave the magnitude as 2.2. He noted a slightly condensed coma 850 across. T. Smith (Australia) saw the comet using 7  50 binoculars and reported a tail extending 20’ in PA 180
. The final days of naked-eye visibility came during May 14–18. Seargent gave the magnitude as 3.2 on the 14th, 3.4 on the 15th, and 4.8 on the 16th. M. L. Clark (Australia) gave the magnitude as 4.4 on the 14th, 4.7 on the 15th, 5.0 on the 16th, and 5.2 on the 17th. Clark made the final naked-eye observation on May 18, when he gave the magnitude as 5.4. Throughout this period, naked-eye observers described the coma as slightly condensed, while observers using some optical aid described it as moderately condensed. On average, the coma was about 300 across. Bouma was using 10  50 binoculars on the 16th and noticed a tail extending about 1.5
in PA 170
. A. R. Pearce (Woodlands, Western Australia, Australia) noted an extension of 0.11
in PA 194
on the 17th and 0.1
in PA 323
on the 18th. Observations continued to dwindle during the remaining days of May. J. da S. Campos (South Africa) followed the comet using his 12-cm refractor and said it faded from magnitude 6.1 on the 19th to 8.7 by the 31st. He added that the coma was initially moderately condensed with a diameter of 120 , but ended the month as slightly condensed and 5’ across. T. Lovejoy (Australia) observed using his 8  30 binoculars and reported the comet faded from magnitude 6.8 on the 19th to 8.3 by the 31st. He noted the coma remained moderately condensed throughout the period, but shrank from 70 to 40 . The comet was continuing its southward motion as June began and was quickly becoming an object only visible to Southern Hemisphere observers. The last two observations made in the Northern Hemisphere came from Bouma on the 4th and P. Poitevin (Belgium) on the 8th, with both observers giving the magnitude as 7.9. Bouma added that the moderately condensed coma was 40 across. The two most prolific observers in the Southern Hemisphere during June were A. F. A. L. Jones (New Zealand) and 8

cometography: a catalog of comets

Pearce. Jones mostly used his 32-cm reflector and noted a magnitude range 9.4–10.9 during the 1st to the 6th and 10.9–11.4 during the 13th to the 17th. Using his 8-cm refractor, Jones noted a general fading from magnitude 8.2 on the 2nd to 10.2 by the 15th. The refractor revealed a coma diameter of 3–40 . Pearce said his 20  65 binoculars revealed the magnitude generally faded from 7.3–7.6 between the 3rd and the 12th, while the moderately condensed coma shrank from 5.50 to 3.50 during the same period. Only a handful of visual observations were obtained in July. Pearce saw the comet with his 15-cm reflector from the 1st to the 5th and noted it faded from 9.6 to 10.2. The coma remained slightly condensed and generally shrank from 3.50 to 2.50 . Clark also saw the comet on the 4th, using his 41-cm reflector. He gave the magnitude as 10.9 and said the slightly condensed coma was 2.80 across. From June onward, the only professional astronomer to follow the comet was A. C. Gilmore (Mt. John University Observatory, Lake Tekapo, New Zealand), who managed to obtain photographs using a 61-cm reflector on June 16, July 11 and 12, and August 14. He estimated the magnitude as 16 on July 11 and 12. The comet also reached a minimum elongation of 67
on the 12th. The comet was last detected on October 4.60 and October 4.64, when Gilmore obtained photographs of the comet which revealed a nuclear magnitude of 18.6. The position on the last date was α = 5h 48.9m, δ = 65
240 (2000). B. L. Lutz and R. M. Wagner (1983) first analyzed the comet’s spectrum using the 175-cm reflector at Lowell Observatory (Arizona, USA) on 1983 May 5 and 6. They detected cyanogen, triatomic carbon, diatomic carbon, the amidyl radical, and oxygen. It was noted that, “The nuclear region, which appeared highly condensed, showed a strong reflective continuum superimposed on the gaseous emissions.” Johnson and Larson (1983) observed the spectrum using the 154-cm reflector on May 6, 7, and 11, noting emission lines of the hydroxyl radical, the imidyl radical, cyanogen, diatomic carbon, triatomic carbon, the amidyl radical, ionized carbon monoxide, and ionized carbon dioxide. There were also lines consistent with diatomic sulfur. They added, “The emissions, including those of the ions, were brighter on the sunward side.” Interestingly, C. B. Cosmovici and S. Ortolani (1984) obtained four spectra using the 182-cm reflector at Asiago Astrophysical Observatory (Italy) on May 9 and noted “about 50 unknown lines.” They also detected the formyl radical and hydrogen sulfide, and strongly suspected formaldehyde, diatomic sulfur, deuterated formylium, and ammonium. Astronomers turned the International Ultraviolet Explorer (IUE) satellite toward the comet on several occasions during the first half of May. On May 6 and 8, M. Festou, P. Benvenuti, C. Cacciari, A. Cassatella, A. Talavera and W. Wamsteker (1983) detected diatomic sulfur, noting that it was confined to the region within 100 kilometers of the nucleus and was weak in 9

cometography: a catalog of comets

intensity. IUE also detected Lyman α, very strong emissions of carbon sulfide, very weak emissions of carbon dioxide, and moderate emissions of the hydroxyl radical. These emissions were all rather typical for comets, except for the carbon sulfide emissions, which were also greater than normal. M. A’Hearn and R. L. Millis (1983) used IUE to observe the comet on May 7 and detected cyanogen and the hydroxyl radical. P. D. Feldman and A’Hearn (1983) observed the comet during May 11.8–13.0 and identified sulfur emission “confined to a region of diameter no larger than 100 km (500 ) around the comet’s nucleus.” Nolthenius’ observation of the comet occulting a star was mentioned above, including the indication that the nucleus was about 30 kilometers across; however, several other observers made observations of the nucleus at other times with large telescopes. Larson said that observations using the 154-cm reflector at magnifications up to 1000 revealed a nuclear condensation about 12 kilometers across that was “unlike nearby star images of the same brightness, appeared to have a sharp edge and uniform brightness.” J. K. Harmon, D. B. Campbell, A. A. Hine, I. I. Shapiro, and B. G. Marsden (1989) observed the comet on May 11 using the Arecibo Radio Telescope (Puerto Rico) and their analysis revealed a diameter ranging from “5 km for a solid-ice surface to 16 km for a surface of loosely packed snow.” R. M. Goldstein, R. F. Jurgens, and Z. Sekanina (1984) used the 64-m Goldstone radio telescope to study the comet on May 11 and 14. They concluded, “The shape of the nucleus probably departs greatly from a sphere with average radii near 3–4 km.” Sekanina (1988) also published an in-depth analysis of the nucleus based on the “optical, radar, infrared, ultraviolet, and microwave-continuum observations made during the week of the object’s close approach to Earth” and established nuclear dimensions of 16 km  7 km  7 km and determined a rotation period of 2.14 days. J. D. Drummond (1983) announced that this comet might produce a meteor shower on May 10.1. He gave the probable radiant as α = 289
, δ = +44
. Marsden reported on IAU Circular number 3811, “P. M. Millman, Herzberg Institute of Astrophysics, reports that preliminary analysis by A. F. Cook and himself of meteor radio data in Ottawa shows no evidence of unusual meteor activity: low power data were obtained over a 72-hr interval centered on May 10.08 UT, high power data over 24 hr. Visual and photographic monitoring by S. Clifton at Marshall Space Flight Center during May 10.0–10.4 also gave negative results.” Drummond writes that his visual observations indicated a definite minor meteor shower associated with the comet. He gave zenithal hourly rates of 5.1 on May 9.47, 3.1–4.1 during May 10.32–10.44, and 2.4–3.2 during May 11.36–11.44. Davies sent the IRAS discovery positions to Marsden, as well as the positions measured by Oja. Combining these with the positions measured by Gibson allowed the calculation of a preliminary orbit on May 4. The resulting perihelion date was 1983 May 21.24. It indicated the comet would pass very close to Earth on May 11. Marsden revised his calculations a 10

cometography: a catalog of comets

couple of days later, when he took 15 positions from the period spanning April 27 to May 6. The result was a perihelion date of May 21.19. This last orbit was an excellent representation as shown by later orbits by Marsden, but a slight revision on May 9 prompted him to remark “A general solution is not viable, although [the eccentricity] could be as small as 0.98.” Marsden took 75 positions from April 27 to July 12 and calculated an elliptical orbit with a perihelion date of May 21.25 and a period of about 1018 years. Three orbits have been calculated that have used positions spanning the entire period of visibility. Marsden used 90 positions, W. Landgraf used 213 positions, and L. Buffoni, A. Manara, and M. Scardia (1987) used 181 positions. All three calculations included full planetary perturbations. The perihelion date was May 21.25. The period was determined as about 1004 years by Marsden, about 961 years by Landgraf, and about 957 years by Buffoni, Manara, and Scardia. E. Everhart and Marsden took Marsden’s orbit and calculated the original and future orbit, finding periods of about 934 and about 920 years, respectively. Marsden’s orbit is given below. T ω Ω (2000.0) i q e 1983 May 21.2529 (TT) 192.8494 49.1023 73.2534 0.991341 0.990115

absolute magnitude: H0 = 9.9, n = 0.5 (Kronk) full moon: Mar. 28, Apr. 27, May 26, Jun. 25, Jul. 24, Aug. 23, Sep. 22, Oct. 21 sources: C. S. Morris, G. S. Keitch, G. E. D. Alcock, G. M. Hurst, B. G. Marsden, J. B. Gibson, J. Davies, D. W. E. Green, J.-C. Merlin, J. E. Bortle, and C. E. Spratt, ICQ, 5 (1983 Apr.), pp. 31–3, 39–41; J. Davies, H. Rickman, T. Oja, J. B. Gibson, G. S. Keitch, G. E. D. Alcock, G. M. Hurst, G. Araki, and D. W. E. Green, IAUC, No. 3796 (1983 May 4); B. G. Marsden, IAUC, No. 3797 (1983 May 4); J. Davies, S. F. Green, B. Stewart, J. B. Gibson, C. S. Morris, J.C. Merlin, J. E. Bortle, and D. W. E. Green, IAUC, No. 3798 (1983 May 6); V. Smith and B. G. Marsden, IAUC, No. 3799 (1983 May 6); J. D. Drummond, IAUC, No. 3801 (1983 May 9); B. G. Marsden, M. A’Hearn, R. L. Millis, M. Festou, P. Benvenuti, C. Cacciari, A. Cassatella, A. Talavera, W. Wamsteker, D. W. E. Green, and A. Hale, IAUC, No. 3802 (1983 May 9); B. L. Lutz, R. M. Wagner, R. H. McNaught, D. W. E. Green, and B. G. Marsden, IAUC, No. 3805 (1983 May 11); T. Kumamori, IAUC, No. 3808 (1983 May 13); P. D. Feldman, and M. F. A’Hearn, IAUC, No. 3809 (1983 May 13); S. M. Larson, J. R. Johnson, P. M. Millman, A. F. Cook, J. E. Bortle, and C. S. Morris, IAUC, No. 3811 (1983 May 18); [corrigenda], IAUC, No. 3814 (1983 May 20); H. Huth, P. Kroll, G. A. Richter, R. Nolthenius, and J. D. Drummond, IAUC, No. 3817 (1983 Jun. 1); C. S. Morris, D. A. J. Seargent, J. da S. Campos, and M. L. Clark, ICQ, 5 (1983 Jul.), pp. 66–7; M. W. Buie, ST, 66 (1983 Jul.), p. 26–7; A. C. Gilmore and B. G. Marsden, MPC, Nos. 8036, 8052 (1983 Jul. 24); 11

cometography: a catalog of comets

G. S. Keitch and T. Smith, ICQ, 5 (1983 Oct.), pp. 92–3; A. C. Gilmore and B. G. Marsden, MPC, Nos. 8220, 8272 (1983 Nov. 20); W. Landgraf, MPC, No. 8381 (1983 Dec. 20); C. B. Cosmovici and S. Ortolani, IAUC, No. 3915 (1984 Feb. 10); R. J. Bouma and P. Poitevin, ICQ, 6 (1984 Apr.), pp. 38–9; A. R. Pearce and M. L. Clark, ICQ, 6 (1984 Jul.), pp. 64–5; S. M. Larson, QJRAS, 27 (1986), p. 107; L. Buffoni, A. Manara, and M. Scardia, AN, 308 (1987), p. 66; E. Everhart and B. G. Marsden, AJ, 93 (1987 Mar.), pp. 753–4; G. M. Hurst, T. Lovejoy, and A. F. A. L. Jones, ICQ, 9 (1987 Jul.), pp. 106–7; Z. Sekanina, AJ, 95 (1988 Jun.), pp. 1876–94; J. K. Harmon, D. B. Campbell, A. A. Hine, I. I. Shapiro, and B. G. Marsden, APJ, 338 (1989 Mar. 15), pp. 1071–93; A. R. Pearce correspondence with G. W. Kronk (2012). Discovered: 1983 May 8.76 (Δ = 1.01 AU, r = 0.51 AU, Elong. = 29
) Last seen: 1983 June 20.06 (Δ = 0.23 AU, r = 1.19 AU, Elong. = 138
) Closest to the Earth: 1983 June 12 (0.0628 AU) Calculated path: AND (Disc), PEG (Jun. 8), VUL–PEG–DEL (Jun. 11), AQL (Jun. 12), SCT–SGR (Jun. 13), OPH-SCO (Jun. 14), LUP (Jun. 16), 1983 V=1983e CEN (Jun. 18) C/1983 J1 (Sugano– Saigusa– Fujikawa)

Three observers in Japan independently discovered this comet in just under 48 minutes. It was found three days before IRAS–Araki–Alcock passed closest to Earth, and would also end up passing very close to our planet during June. The comet was first discovered on 1983 May 8.76 by M. Sugano (Minami, Hyogo, Japan), at a position of α = 1h 37m, δ = +39
550 (2000). It was then independently discovered on May 8.77 by Y. Saigusa (Kofu, Yamanashi, Japan) and on May 8.79 by S. Fujikawa (Onohara, Kagawa, Japan). All three observers estimated the magnitude as 7 and noted the comet was diffuse and uncondensed. Sugano found the comet using his 15-cm reflector and had spent 450 hours searching for comets since 1968 before he found this, his first comet. Saigusa discovered the comet using his 20-cm reflector. Fujikawa found the comet using 12  120 binoculars. Several independent confirmations were made on May 9. E. Mayer (Barberton, Ohio, USA) saw the comet on May 9.38. He estimated the magnitude as 7 and noted a condensation within a coma 20 across. On May 9.43, E. Everhart (Chamberlin Observatory field station, Bailey, Colorado, USA) photographed the comet using the 41-cm reflector and noted a “thin, straight tail” extending about 0.5
in PA 315
. At the Anderson Mesa Station of Lowell Observatory (Arizona, USA), B. A. Skiff and C. B. Luginbuhl photographed the comet on May 9.46. They described the comet as diffuse, with a small condensation, and noted a narrow tail over 1.5
long. K. Kanai (Japan) saw the comet using his 15-cm reflector on May 9.75. He gave the magnitude as 7.7 and said the coma was 1.80 across. M. Koishikawa (Sendai Observatory, Miyagi, 12

cometography: a catalog of comets

Japan) photographed the comet on May 9.76, but did not provide a physical description. A number of experienced visual observers began to follow the comet on May 10. R. W. Panther (England) gave the magnitude as 7.0, using 20  80 binoculars. He said the coma was well condensed and 30 across. J. E. Bortle (Stormville, New York, USA) saw the comet using his 32-cm reflector. He gave the magnitude as 8.1 and reported a well-condensed coma 1.50 across. D. E. Machholz (Loma Prieta, California, USA) used his 25-cm reflector and gave the magnitude as 7.8. He said the well-condensed coma was 1.70 across. The comet was well observed during the remainder of May, during which time it faded as it moved away from the Sun, despite the fact that its distance from Earth was decreasing. J. D. Shanklin (Cambridge, England) was the most prolific observer. Using 20  80 binoculars, he gave the magnitude as 7.9 on the 12th, 7.6 on the 13th, 8.8 on the 15th, 8.9 on the 16th and 17th, and 8.7 on the 20th. The coma generally remained moderately condensed, although Shanklin noted the diameter varied from day to day, as he gave values of 1.80 on the 12th, 1.40 on the 13th, 10 on the 15th, 2.50 on the 16th, 2.10 on the 17th, and 1.60 on the 20th. Shanklin only used his 20-cm refractor on the 25th and 26th, noting the magnitude as 9.7 and 10.0, respectively. He said the coma appeared only slightly condensed, with a diameter of 1.40 . Machholz saw the comet using his 25-cm reflector on the 14th, 15th, 17th, and 20th, giving the magnitude as 7.7, 8.0, 8.2, and 8.3, respectively. The moderately condensed coma generally shrank from 2.80 to 2.20 between the 14th and 17th; however, Machholz estimated the diameter as 40 on the 20th. Also, on the 15th, he noted a tail extending 0.05
in PA 290
. Several other observers also noted a tail. Bortle said it extended 200 in PA 310
on the 14th and 120 in PA 295
on the 18th. J.-C. Merlin (Le Creusot, France) noted the tail extended 8.40 in PA 293
on the 18th and 6.00 in PA 326
on the 22nd. The comet was followed at several observatories from May 11 to 31, although only a few provided physical descriptions. S. J. Bus and E. H. Bus (Palomar Observatory, California, USA) photographed the comet on the 11th, using the 46-cm Schmidt telescope, and noted a tail extending 1.5
toward the northwest. On May 29, R. E. McCrosky and C.-Y. Shao (Oak Ridge Observatory, Cambridge, Massachusetts, USA) photographed the comet using the 40-cm astrograph and described it as large and extremely diffuse. That same night, Everhart photographed the comet and described it as large, faint, and uncondensed. The comet attained its most northerly declination of +41
on May 23. The comet continued to be well observed during the first ten days of June, partly because it started brightening again as it neared Earth. Among the many visual observers were C. S. Morris (Harvard, Massachusetts, USA), Merlin, and D. A. J. Seargent (The Entrance, New South Wales, Australia), all of whom reported the coma exhibited little or no condensation. Morris saw the comet on the 1st using his 26-cm reflector and 13

cometography: a catalog of comets

estimated the magnitude as 9.5. He noted the coma was about 50 across. Merlin was using his 15-cm reflector on the 3rd and gave the magnitude as 8.8. He said the coma was 50 across, while a tail extended 4.80 in PA 259
. Merlin made additional observations on the 4th and 5th, estimating the magnitude as 8.4 and 8.2, respectively. The coma increased from 7.50 to 90 across, while the 5.40 long tail extended toward 275
on the 4th and 252
on the 5th. Seargent made one of the first observations from the Southern Hemisphere on the 7th. Using 15  80 binoculars, he estimated the magnitude as 7.5 and said the coma was about 200 across. Seargent’s next observation on the 8th revealed a magnitude of 7.7 and a coma diameter of 160 . The comet was seen by Morris and Seargent on the 9th, with the magnitude given as 7.4–7.6. The coma diameter was estimated as 240 by Morris and about 120 by Seargent. Observations by Merlin and Seargent on the 10th revealed a magnitude of 6.8–7.0. The diameter of the coma was estimated as >160 by Seargent and about 300 by Merlin. A number of photographs were also acquired during the first ten days of June. On the 4th, A. Mrkos (Klet Observatory, Czech Republic) noted the comet was very diffuse, while Everhart said it was more condensed than on May 29. McCrosky and Shao said the comet was extremely diffuse on the 6th and 9th. H. L. Giclas (Lowell Observatory, Arizona, USA) described the comet as very diffuse on the 7th. On June 9, E. S. Barker (McDonald Observatory, Texas, USA) used the 272-cm reflector and noted the comet had a very faint, but essentially stellar condensation of magnitude 18–19. That same night, R. L. Waterfield (Woolston Observatory, England) noted the coma was about 50 across and almost completely uncondensed. The comet was closest to Earth during the period of June 11 to 14, during which time the declination changed from +24
to 30
. On the 11th, the magnitude was given as about 6.5 by Morris and 6.8 by Seargent, while the diameter of the uncondensed coma was given as 200 and 260 , respectively. That same night, G. Schwartz (Oak Ridge Observatory) acquired a photograph using the 155-cm reflector and noted the comet appeared extremely diffuse. Merlin and Morris made their final observations on the 12th, giving magnitude estimates of 6.6 and 6, respectively. Merlin said the uncondensed coma was 250 across, while Morris noted a slight condensation and a diameter of 300 . Seargent gave the magnitude as 6.8 on the 13th and said the uncondensed coma was 390 across. The comet reached a maximum elongation of 178
on June 14, during which Seargent gave the magnitude as 6.5. He said the uncondensed coma was 340 across. Four observers reported seeing the comet with the naked eye during the same period noted above. On June 11, R. A. Keen (Colorado, USA) saw it without optical aid as well as through 7  35 binoculars. He estimated the total brightness as 5.9 through the binoculars. Keen made another naked-eye observation on June 12, at which time he estimated the comet’s brightness as 5.6 through 7  35 binoculars. S. J. O’Meara (Harvard University, Massachusetts, USA) and Bortle glimpsed the comet with the 14

cometography: a catalog of comets

naked eye on June 12. Bortle estimated the comet’s magnitude as 5.6 in a 5-cm refractor. G. S. Keitch (England) made the final naked-eye observation on June 13, estimating the magnitude as 5.5. All four observers estimated the naked-eye coma diameter as 1
. Only a few observations were reported on June 15 and 16. On the first date, the magnitude was given as 6.2 by Keitch, 5.3 by K. Marshall (St. Ives, Cambridgeshire, United Kingdom), 6.9 by Keen, and 8.0 by T. Lovejoy (Australia). Keitch was using 10  50 binoculars and noted a very slightly condensed coma 330 across, while Marshall was using his 30-cm reflector and said the coma was only 20 across. On June 16, Seargent observed with his 10  50 binoculars and gave the magnitude as 7.8. He said the coma was uncondensed and 170 across. The final astrometric position of the comet was obtained on June 17.27, when J. B. Gibson (Palomar Observatory) photographed it at low altitude using the 122-cm Schmidt telescope. The position was given as α = 15h 33.7m, δ = 38
200 (2000). The final visual observation was obtained on June 20.06, when Marshall gave the magnitude as 7.3. He also noted a well-condensed coma 0.90 across. The first observation of the comet’s spectrum was by Barker (McDonald Observatory) on June 9, using the 272-cm reflector. He noted emissions of cyanogen, diatomic carbon, and triatomic carbon, but there was little or no continuum. M. S. Hanner, R. L. Newburn, H. Spinrad, and G. J. Veeder (Lick Observatory, California, USA) obtained spectra of the comet during June 12–14 using the 305-cm Shane reflector and the 102-cm Nickel reflector. They detected the amidyl radical, cyanogen, diatomic carbon, triatomic carbon, and oxygen. They reported that, compared to the abundance of oxygen, the other molecules had “unusually low” production rates as compared to other comets. S. Wyckoff and P. A. Wehinger (Kitt Peak National Observatory, Arizona, USA) examined the spectrum using the 229-cm reflector on June 13. They noted emissions of the hydroxyl radical, the imidyl radical, cyanogen, diatomic carbon, and triatomic carbon. The team of D. B. Campbell, A. Forni, J. K. Harmon, A. A. Hine, B. G. Marsden, G. H. Pettengill, and I. I. Shapiro announced observations made on 1983 June 11.4 and June 12.4 using the 305-m radio telescope of Arecibo Observatory (Puerto Rico). They received radar echoes from the comet that were “relatively substantially weaker than those from comet [C/1983 H1], indicating a much smaller nucleus.” They concluded that the nucleus was no more than a few hundred meters in diameter. T. Urata and Marsden independently calculated the first orbits. Urata used four positions obtained during the period of May 9–12 and determined the perihelion date as 1983 May 1.26. Marsden used nine positions obtained during the period of May 9–12 and determined the perihelion date as May 1.27. Marsden published several additional revisions and, at the beginning of June, he noted that a general solution, using 15

cometography: a catalog of comets

27 positions from May 9–29, revealed a perihelion date of May 1.33 and an eccentricity of 0.9999. Two orbits have been calculated using positions spanning the period of May 9 to June 17. Marsden published an orbit on July 24, which used 46 positions and included perturbations by all nine planets. He determined a hyperbolic orbit with a perihelion date of May 1.33 and an eccentricity of 1.00002. L. Buffoni, A. Manara, and M. Scardia (1987) took 47 positions, but did not include planetary perturbations. They determined an elliptical orbit with a perihelion date of May 1.32 and a period of about 33 thousand years. Marsden’s orbit is given below. Four independent predictions of a potential meteor shower from this comet came forth shortly before mid-June. These came from R. H. McNaught (Royal Greenwich Observatory, England), I. Hasegawa (Saidaijinogami, Nara, Japan), V. Vanýsek (Department of Astronomy, Charles University, Prague, Czech Republic), and L. Kresák (Astronomical Institute, Slovak Academy of Sciences, Bratislava, Slovakia). The details of McNaught’s prediction received the greatest exposure when it was published in the June 13 issue of the International Astronomical Union Circulars. He said Earth would pass closest to the comet’s orbit on June 14.7, just 2.9 days after the comet passed this point. He added that Earth would then be 0.038 AU inside the comet’s orbit. McNaught gave the probable radiant as α = 21
, δ = +42
. The calculated details from the other astronomers were very similar, although Vanýsek and Kresák predicted a radiant near α = 22.5
, δ = +43
. M. Šimek (Ondřejov Observatory, Czech Republic) used the 25kW pulsed radar operating at a frequency of 37.5 MHz during June 12–15. Although six known meteor showers also occurred during this period, Šimek and P. Pecina (1984) reported that during a period of one hour centered on June 14.40, there was a “small increase of rate of meteors with durations 6.30 in PA 131
. On February 13.33, Scotti reported the secondary nucleus was located at 8.000 in PA 122
. K. J. Meech (Mauna Kea, Hawaii, USA) acquired CCD images of the comet using the 224-cm reflector and a Mould R filter. She reported a round condensation or secondary nucleus near the main nucleus. Meech’s follow-up observations on the 14th, 15th, and 16th consistently revealed the magnitude of the main nucleus as 14.6, while that of the secondary was fainter than 15.2. Meech said the secondary nucleus was situated 9.100 0.100 from the main nucleus in PA 119
2
. Following the announcement of this discovery, D. C. Jewitt and J. X. Luu (Kitt Peak National Observatory, Arizona, USA) acquired CCD images on February 22, using the 236-cm reflector and a Mould R filter. They noted the secondary nucleus was located 8.700 east and 4.700 south of the primary nucleus and was 2.00.2 magnitudes fainter than the primary and appeared broader than stellar images. Larson and Levy acquired CCD images on the 23rd, using the 154-cm reflector and an R filter. They noted the secondary nucleus was more diffuse than nearby 217

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stars, while “a 300–560 nm CCD spectrum showed only continuum.” An analysis of these observations was published by Z. Sekanina (Jet Propulsion Laboratory, California, USA) on February 29. He said the nucleus may have split on 1987 August 317 days, when the comet was still 2.3 AU from the Sun. Only a few visual observations were made during March. Jacobson saw the comet using his 25-cm reflector on the 6th, giving the magnitude as 12.4 and reporting a slightly condensed coma 1.60 across. Hale observed the comet using his 41-cm reflector on the 7th and 10th. He gave the magnitude as 13.2 and 13.5, respectively. Morris saw the comet on the 12th, using his 26-cm reflector. He noted a magnitude as 13.5 and reported a very slightly condensed coma 1.00 across. Shanklin used a 20-cm reflector to see the comet on the 21st. He gave the magnitude as 12.0 and noted a slightly condensed coma 1.70 across. Morris attempted to see the comet with his reflector on the 22nd, but was unsuccessful. He concluded the magnitude was fainter than 13.5. T. Kojima (Chiyoda, Gunma, Japan) photographed the comet on the 10th and estimated the magnitude as 15. He indicated the secondary nucleus was located 10–1300 from the primary nucleus. Meech (Cerro Tololo Inter-American Observatory, Chile) acquired CCD images on March 23 and 25, using the 152-cm reflector, which revealed both nuclei. On the 23rd, she noted the secondary nucleus was situated 12.300 in PA 115.5
from the primary. A visual observation appears to have been made by Jacobson on April 7, when he estimated the magnitude as 12.5 while using his 25-cm reflector; however, Hale failed to spot the comet on the 8th, 10th, and 19th while using his 41-cm reflector. Hale surmised that the comet must have been fainter than magnitude 13.5. T. Gehrels and Scotti acquired CCD images using the 91-cm reflector on the 12th. They gave the magnitude as 15.7 and said the magnitude of the primary nucleus was 18.6, while a tail extended 4.50 toward PA 122
. Gehrels and Scotti noted the secondary nucleus was situated 12.200 0.700 away from the primary in PA 120
3
. Meech (Mauna Kea) acquired a couple of CCD images on both April 16 and 17 using the 224-cm reflector. The secondary nucleus was located 12–1300 toward PA 111–119
. The final visual observation was made on May 7, when Levy used the 154-cm reflector to give the magnitude as 13.9. Meech acquired CCD images of the comet on the 18th and 19th. She indicated the secondary nucleus was located about 1200 toward PA 117–120
. No further observations were made during the next three months as the comet passed 1.2
from the Sun on July 11. Observations resumed during September. Hale attempted to observe the comet using his 41-cm reflector on the 8th, but was unsuccessful. He suggested the comet was probably fainter than magnitude 13.3. Meech acquired CCD images of the comet on the 10th, 11th, and 12th, using the 224-cm reflector. She gave the magnitude of the primary nucleus as 17.6 on 218

cometography: a catalog of comets

the 12th. Meech indicated the secondary nucleus was located about 1200 from the primary in PA 148
on all three nights. The comet was next detected during December, when Meech acquired images on the 9th and 11th. She indicated the secondary nucleus was situated about 2300 from the primary in PA 136
on the first date and about 2500 in PA 133
on the second date. The comet reached a maximum elongation of 174
on 1989 January 3. Two observatories acquired images of the comet during the remainder of January. Meech (Cerro Tololo Inter-American Observatory) detected the comet on the 7th and 9th using the 91-cm reflector. Her measurements of the distance of the secondary nucleus from the primary ranged from 26.300 to 30.800 , while the position angle was within the range of 126
to 129
. Larson and Levy obtained CCD images on the 11th using the 154-cm reflector. They noted the secondary nuclear condensation was separated from the primary by 30.500 in PA 125.5
. It was also two magnitudes fainter and “somewhat extended.” On January 25, Sekanina used 12 positions obtained during the period spanning 1987 December and 1989 January to determine that the nuclei likely split around 1987 September 115. The comet attained its most northerly declination of +30
on March 21. Meech acquired additional images on April 6, but provided no physical descriptions. The comet was last detected during 1989 April 10.13–10.14 and April 11.17–11.19, when Meech (Kitt Peak National Observatory) acquired CCD images using the 402-cm reflector. The secondary nucleus was 2.0 magnitudes fainter than the primary on both nights and “was no longer centrally condensed.” On the 10th, she noted the secondary nucleus was located 36.300 from the primary in PA 115.7
. The comet’s position on the final image was α = 6h 19.7m, δ = +29
460 (2000). Meech (Mauna Kea) used the 224-cm reflector to acquire CCD images of the comet’s predicted position on 1991 February 13/14. Although the sky was clear, seeing was poor, and fog eventually forced an early closure of the dome. No trace of the comet was found. The earliest observation of the comet’s spectrum was obtained by Larson and Levy (1986) on 1986 September 2.3 and September 3.3. Using the 154-cm reflector, they detected a strong dust continuum and noted the only emission was cyanogen, “which extends at least 10 from the nucleus.” S. Wyckoff and S. Tegler (1986) used the 447-cm Multiple-Mirror Telescope at the Fred Lawrence Whipple Observatory (Mt. Hopkins, Arizona, USA) and detected cyanogen, triatomic carbon, and diatomic carbon on 1986 November 28–30. P. Palmer, I. de Pater, and L. Snyder (1987) used the Very Large Array (New Mexico, USA) to observe the comet on 1987 February 6 and 7. They detected the emission of the hydroxyl radical. J. R. Ducati and R. D. D. Costa (1987) reported details of their observations of the spectrum using the 61-cm Lowell telescope at Cerro Tololo InterAmerican Observatory (Chile) on 1987 April 16, 18, 19, 23, 24, and 25. They detected diatomic carbon, triatomic carbon, ionized water, and ionized 219

cometography: a catalog of comets

carbon monoxide. They noted that the strong emission of the latter molecule “contrasts with that in [1P/Halley], where it was almost absent.” Using a telescope on NASA’s Kuiper Airborne Observatory, H. P. Larson, M. J. Mumma, H. A. Weaver, and S. Drapatz (1987) detected water vapor in the comet during 1987 April 12, 14, and 17. The first parabolic orbit was calculated by B. G. Marsden and was published on 1986 August 11. Marsden used 16 positions from August 6–10 and gave the perihelion date as 1987 April 22.59. He added that the comet “should become a rather conspicuous southern-hemisphere object around perihelion.” Marsden published a revision on August 19. This used 29 positions from August 5–16 and determined the perihelion date as April 21.45. Additional revisions of the parabolic orbit were published by Marsden on September 17 and October 17, which revealed perihelion dates of April 20.86 and April 20.78, respectively. The first hyperbolic orbit was published by Marsden on December 16. This used 100 positions from August 5 to November 30. The perihelion date was given as April 20.78, while the eccentricity was 1.00037. Marsden used this orbit to determine the original and future orbits and published the results on 1987 January 5. Both orbits proved elliptical with periods of about six million years and about 48 thousand years, respectively. Marsden suggested “the comet is a ‘new’ one from the Oort Cloud.” Additional hyperbolic orbits were calculated by Marsden and T. Kobayashi during 1987. The perihelion date was consistently given as April 20.78, while the eccentricity was 1.00032–1.00036. Kobayashi published hyperbolic orbits on 1988 February 2, 1988 September 25, and 1989 August 17, all of which had perihelion dates of April 20.78. The eccentricity was within the range of 1.00031–1.00032. Kobayashi also determined nongravitational terms within the range of A1 = +1.87 to +1.90 and A2 = +0.0505 to +0.1410. The first orbit to use positions spanning the entire period of visibility was calculated by B. Todorovic-Juchniewicz (1991). Using 642 positions, full planetary perturbations, and solving for nongravitational effects, he determined the perihelion date as April 20.78 and the eccentricity as 1.00031. The nongravitational terms were given as A1 = +1.7692, A2 = +0.0515, and A3 = +0.03. Meech, G. Knopp, T. L. Farnham, and Green (1995) published a detailed analysis of this comet, including the calculation of orbits for both the primary and the secondary nuclei. For the primary nucleus, they used 191 positions spanning the entire apparition. The result was a perihelion date of April 20.78 and an eccentricity of 1.00031. They also determined the nongravitational terms as A1 = +1.72 and A2 = +0.0294. For the secondary nucleus, they used 25 positions spanning 1988 February 14 to 1989 April 10. The result was a perihelion date of April 20.89 and an eccentricity of 1.00080. These orbits are given below, with the first representing the primary and the second representing the secondary. 220

cometography: a catalog of comets T ω Ω (2000.0) i q e 1987 Apr. 20.7809 (TT) 238.3071 111.6660 147.1192 1.199651 1.000312 1987 Apr. 20.8853 (TT) 238.3135 111.6661 147.1192 1.199345 1.000797

absolute magnitude: H0 = 5.5, n = 3.0 (Kronk) full moon: Jul. 21, Aug. 19, Sep. 18, Oct. 17, Nov. 16, Dec. 16, 1987 Jan. 15, Feb. 13, Mar. 15, Apr. 14, May 13, Jun. 11, Jul. 11, Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2, Mar. 3, Apr. 2, May 1, May 31, Jun. 29, Jul. 29, Aug. 27, Sep. 25, Oct. 25, Nov. 23, Dec. 23, 1989 Jan. 21, Feb. 20, Mar. 22, Apr. 21 sources: C.-Y. Shao and G. Schwartz, HOPL (1986); C. Wilson, G. Schwartz, C. Pollas, R. E. McCrosky, C. S. Morris, and D. W. E. Green, IAUC, No. 4241 (1986 Aug. 6); E. F. Helin, T. Seki, C. S. Morris, and B. G. Marsden, IAUC, No. 4243 (1986 Aug. 11); C. Wilson, C. Pollas, R. E. McCrosky, E. F. Helin, and B. G. Marsden, MPC, Nos. 10999, 11047 (1986 Aug. 19); J.-C. Merlin, IAUC, No. 4249 (1986 Aug. 28); S. M. Larson, D. H. Levy, J. V. Scotti, and J.-C. Merlin, IAUC, No. 4253 (1986 Sep. 15); B. G. Marsden, IAUC, No. 4255 (1986 Sep. 17); B. G. Marsden, MPC, No. 11153 (1986 Sep. 18); A. Hale, IAUC, No. 4258 (1986 Sep. 24); J.-C. Merlin, IAUC, No. 4260 (1986 Oct. 7); B. G. Marsden, MPC, No. 11236 (1986 Oct. 17); M. V. Zanotta and J. Kobayashi, IAUC, No. 4266 (1986 Oct. 30); M. V. Zanotta, IAUC, No. 4271 (1986 Nov. 17); J. Kobayashi and C. S. Morris, IAUC, No. 4275 (1986 Nov. 25); B. G. Marsden, MPC, No. 11429 (1986 Dec. 16); S. Wyckoff and S. Tegler, IAUC, No. 4284 (1986 Dec. 17); J.-C. Merlin, R. A. Keen, C. S. Morris, and M. V. Zanotta, IAUC, No. 4285 (1986 Dec. 17); B. G. Marsden, IAUC, No. 4294 (1987 Jan. 5); A. Hale, C. S. Morris, and M. V. Zanotta, IAUC, No. 4298 (1987 Jan. 15); P. Palmer, I. de Pater, L. Snyder, and R. H. McNaught, IAUC, No. 4314 (1987 Feb. 18); R. H. McNaught and G. J. Garradd, IAUC, No. 4323 (1987 Feb. 28); I. Ferrin, G. J. Garradd, J. da S. Campos, and A. Hale, IAUC, No. 4337 (1987 Mar. 9); G. J. Garradd, M. Clilverd, J. Campos, and V. F. de Assis Neto, IAUC, No. 4355 (1987 Mar. 31); J.-C. Merlin, D. A. J. Seargent, R. J. Bouma, G. J. Garradd, M. Möller, W. Hasubick, M. V. Zanotta, and C. S. Morris, ICQ, 9 (1987 Apr.), pp. 68–74; G. J. Garradd, IAUC, No. 4364 (1987 Apr. 10); B. G. Marsden, MPC, No. 11738 (1987 Apr. 14); J. R. Ducati and R. D. D. Costa, IAUC, No. 4371 (1987 Apr. 23); J. R. Ducati, R. D. D. Costa, and C. M. Humphries, IAUC, No. 4372 (1987 Apr. 24); G. J. Garradd, V. F. de Assis Neto, R. H. McNaught, and J. Campos, IAUC, No. 4373 (1987 Apr. 24); J. R. Ducati, R. D. D. Costa, V. F. de Assis Neto, and G. J. Garradd, IAUC, No. 4375 (1987 Apr. 27); G. J. Garradd and D. A. J. Seargent, IAUC, No. 4379 (1987 Apr. 30); B. G. Marsden, MPC, No. 11845 (1987 May 13); G. W. Wolf and G. J. Garradd, IAUC, No. 4391 (1987 May 14); A. Hale and G. J. Garradd, IAUC, No. 4397 (1987 May 25); T. Brooke, R. Knacke, and A. Tokunaga, IAUC, No. 4399 (1987 May 30); H. P. Larson, M. J. Mumma, H. A. Weaver, S. Drapatz, G. J. Garradd, and G. W. Wolf, 221

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IAUC, No. 4403 (1987 Jun. 4); A. Hale and G. W. Wolf, IAUC, No. 4411 (1987 Jun. 25); A. Hale, M. V. Zanotta, M. L. Clark, G. J. Garradd, A. R. Pearce, and W. Hasubick, ICQ, 9 (1987 Jul.), pp. 101, 113–15; V. F. de Assis Neto and G. W. Wolf, IAUC, No. 4439 (1987 Aug. 20); G. W. Wolf, IAUC, No. 4445 (1987 Sep. 3); W. C. Morrison, R. H. McNaught, A. F. A. L. Jones, A. R. Pearce, and A. Hale, ICQ, 9 (1987 Oct.), pp. 159–62; J. Kobayashi, MPC, No. 12454 (1987 Nov. 5); J. Kobayashi and A. Hale, IAUC, No. 4491 (1987 Nov. 19); R. A. Keen, A. Hale, J. D. Shanklin, and C. S. Morris, IAUC, No. 4503 (1987 Nov. 27); E. A. Jacobson, M. L. Clark, R. J. Bouma, A. Hale, A. R. Pearce, J. D. Shanklin, C. S. Morris, M. V. Zanotta, and J. V. Scotti, ICQ, 10 (1988 Jan.), p. 5; J. V. Scotti, MPC, Nos. 12629, 12632; M. V. Zanotta, J. Kobayashi, A. Hale, and J. D. Shanklin, IAUC, No. 4536 (1988 Jan. 25); T. Kobayashi, MPC, No. 12797 (1988 Feb. 2); K. J. Meech, A. Hale, and C. S. Morris, IAUC, No. 4552 (1988 Feb. 22); S. M. Larson, D. H. Levy, J. V. Scotti, D. C. Jewitt, and J. X. Luu, IAUC, No. 4555 (1988 Feb. 25); Z. Sekanina, IAUC, No. 4557 (1988 Feb. 29); A. R. Pearce, D. A. J. Seargent, R. A. Keen, and A. Hale, ICQ, 10 (1988 Apr.), pp. 39–40; J. V. Scotti, MPC, Nos. 12857, 12865 (1988 Apr. 2); T. Kojima, T. Gehrels, and J. V. Scotti, MPC, Nos. 13004, 13007 (1988 May 1); A. Hale, IAUC, No. 4590 (1988 May 5); J. V. Scotti, MPC, Nos. 13110–11 (1988 May 31); D. H. Levy, IAUC, No. 4607 (1988 Jun. 7); W. C. Morrison, A. Hale, and J. D. Shanklin, ICQ, 10 (1988 Jul.), p. 69; T. Kobayashi, MPC, No. 13596 (1988 Sep. 25); E. A. Jacobson and C. S. Morris, ICQ, 10 (1988 Oct.), p. 112; K. J. Meech, MPC, No. 13782 (1988 Nov. 23); S. M. Larson, D. H. Levy, and Z. Sekanina, IAUC, No. 4722 (1989 Jan. 25); M. L. Clark, ICQ, 11 (1989 Apr.), p. 31; T. Kobayashi, MPC, No. 14903 (1989 Aug. 17); K. J. Meech, MPC, Nos. 15604–5 (1990 Jan. 11); K. J. Meech, MPC, Nos. 16296, 16302 (1990 Jun. 8); A. Nakamura, ICQ, 12 (1990 Jul.), pp. 80–1; B. Todorovic-Juchniewicz, MPC, No. 17939 (1991 Mar. 30); D. E. Machholz, JALPO, 35 (1991 Jun.), pp. 49–52; J. D. Shanklin, ICQ, 15 (1993 Oct.), pp. 155–6; K. J. Meech, G. Knopp, T. L. Farnham, and D. W. E. Green, Icarus, 116 (1995), pp. 46–76. 26P/Grigg– Recovered: 1986 August 12.16 (Δ = 3.74 AU, r = 3.22 AU, Elong. = 52
) Skjellerup Last seen: 1989 December 27.40 (Δ = 4.57 AU, r = 4.93 AU, Elong. = 106
) Closest to the Earth: 1987 July 10 (0.8635 AU) 1987 X=1986m Calculated path: ORI (Rec), MON (Sep. 7), LEP (1987 Jan. 10), ORI (Jan. 29), MON (Apr. 13), CMi (May 3), CNC (May 20), LEO (Jun. 9), VIR (Jul. 10), BOO (Jul. 29), VIR (Aug. 17), SER (Aug. 18), HER (Sep. 3), SER (Sep. 5), OPH (Sep. 6), SER (Oct. 6), AQL (Oct. 23), AQR (Dec. 17), PEG (1988 Feb. 12), PSC (Mar. 8), PEG (Mar. 29), PSC (May 22), PEG (Sep. 15), PSC (Nov. 25), ARI (1989 Jun. 2), PSC (Oct. 20) S. Nakano (1985, 1986) took 68 positions from 1966–1982, included full planetary perturbations, and solved for nongravitational effects. After 222

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integrating the comet’s motion to this apparition, he predicted the next perihelion date as 1987 June 18.05. This comet was recovered by K. Birkle (Calar Alto Observatory, Almería, Spain) on 1986 August 12.16, at a position of α = 5h 52.6m, δ = +11
250 (2000). He was using the 350-cm reflector and a CCD at prime focus. Birkle said the comet was stellar, with an R magnitude of about 22. Four additional CCD images were obtained during August 13.15–13.17. These were the only other observations of 1986. The comet reached a maximum elongation of 147
on December 26. Observations resumed at the beginning of 1987. T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired three CCD images on January 3 using the 91-cm reflector. The magnitude was given as 19.7. After having moved southward since its recovery, the comet attained a declination of 11
on January 18 and then began a northerly motion. P. A. Wehinger and M. J. S. Belton (Cerro Tololo Inter-American Observatory, Chile) acquired several CCD images during January 31, February 1, and February 2, using the 402-cm reflector. They said the magnitude was 20.6 on the February images. The only observations made during March and April came from Scotti. During March, he determined the nuclear magnitude as 19.1 on the 2nd and 18.6 on the 3rd, while he gave the magnitude as 18.7 on the 27th. His observation during April came on the 25th, but no physical description was provided. During May, the comet was photographed by observers at Perth Observatory (Bickley, Western Australia, Australia) on the 19th and at Calar Alto Observatory on the 21st and 28th. A. Hale (Las Cruces, New Mexico, USA) tried to visually spot the comet on the 17th, using a 20-cm reflector, but was unsuccessful. He concluded it was probably fainter than magnitude 12.5. He switched to his 41-cm reflector on the 29th and 30th, but the comet was still not found. He concluded the comet was fainter than magnitude 13.0. It should be noted that IAU Circular number 4410 reported that E. A. Jacobson (Evansville, Minnesota, USA) visually spotted the comet on May 29 using a 25-cm reflector. He gave the magnitude as 12.5. It further reported that Jacobson also saw the comet on June 1 and gave the magnitude as 12.7. As June began, the comet was photographed by astronomers at Calar Alto Observatory using the 80-cm Schmidt telescope. The images were obtained on the 3rd, 4th, and 5th, but no descriptive information was provided. Moonlight prevented observations during the next several days and the comet reached a minimum elongation of 61
on the 6th. Hale and Jacobson reported observations on the 14th. Hale gave the magnitude as 11.7 and noted a very slightly condensed coma. Jacobson gave the magnitude as 11.9 and said the coma was about 1.50 across and very slightly condensed. C. S. Morris (Lockwood Valley, California, USA) saw the comet on the 15th using his 26-cm reflector and gave the magnitude as 11.5. He added that the coma was 1.70 across and very slightly condensed. During 223

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the remainder of the month, Hale and Morris saw little change in the comet’s appearance. Hale gave magnitudes of 11.5–11.9 during the 17th to the 30th, while Morris gave magnitudes of 11.6 to 12.3. They said the coma remained very slightly condensed. Although Morris gave the coma diameter as 1.70 and 1.90 on the 18th and 23rd, respectively, he estimated the diameter as 4.90 on the 27th. After having moved northward since mid-January, the comet attained a declination of +13
on July 7 and then began a southerly motion. The comet seems to have faded during July. Hale saw the comet on the 18th and gave the magnitude as 11.6, while another observation on the 25th revealed a magnitude of 12.1. Morris saw the comet on the 19th and 26th, giving the magnitude as 12.1 and 12.4, respectively. He added that the coma was uncondensed on the 19th and 3.30 across and very slightly condensed on the 26th and 2.70 across. Observations were few during August. The only visual observations were made by R. J. Bouma (Netherlands) and M. Amoretti (Sanremo, Italy). Bouma saw the comet using his 25-cm reflector on the 3rd and gave the magnitude as 12.2. He described the coma as uncondensed and 1.50 across. Amoretti saw the comet on the 19th using a 35-cm reflector and gave the magnitude as 13.1. He noted a strongly condensed nuclear region about 0.600 across. Hale tried to observe the comet on the 15th using his 41-cm reflector, but was unsuccessful. He suggested it was then fainter than magnitude 13.0. Among four professional observatories that acquired images of the comet during the month, only those at Steward Observatory provided physical descriptions. T. Gehrels and J. V. Scotti acquired CCD images on August 18 using the 91-cm reflector, giving the magnitude as 16.4 and the nuclear magnitude as 19.3. They added that a tail extended 4200 toward PA 102
. Only a few observations were made during the remainder of the year. The comet reached a maximum elongation of 81
on September 8. A. C. Gilmore (Mt. John University Observatory, Lake Tekapo, New Zealand) acquired two photographs on September 26, using a 61-cm reflector, but provided no physical description. Gehrels and Scotti acquired a couple of images on September 27, which revealed a magnitude of 17.1. After having moved southward since early July, the comet attained a declination of 4
on November 17 and then began a northerly motion. The comet was too close to the Sun for observations as 1988 began, reaching a minimum elongation of 12
on March 6. After having moved northward since last November, the comet attained a declination of +19
on August 2 and then began a southerly motion. K. J. Meech (Mauna Kea, Hawaii, USA) made the only observations during the year. Using the 224-cm reflector, she acquired two CCD images on both September 10 and 11. On both nights, the total exposure times were 2400 seconds. Meech estimated the nuclear magnitude as 22 on the second night. The comet reached a maximum elongation of 167
on September 29. 224

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After having moved southward since last August, the comet attained a declination of +7
on 1989 January 1 and then began a northerly motion. No observations were possible during the early part of the year because the comet was situated only 5
from the Sun on April 8. Meech acquired six CCD images of the comet on August 2, but provided no physical description. After having moved northward since the beginning of the year, the comet attained a declination of +17
on August 5 and then began a southerly motion. It reached a maximum elongation of 178
on October 22. The comet was last detected during 1989 December 27.37–27.42, when Meech acquired five CCD images using the 224-cm reflector and an R filter. The total exposure time was 3000 seconds. She estimated the magnitude as 24 and wrote “no coma evident.” The comet’s position on December 27.40 was α = 1h 17.9m, δ = +8
410 (2000). The comet passed aphelion on 1990 January 3. Images of the spectrum of this comet were acquired by Wehinger and Belton (Cerro Tololo Inter-American Observatory) during 1987 January 31 to February 2 using the 402-cm reflector. A continuum was detected, but they also detected emission from cyanogen and triatomic carbon. Multiple apparition orbits have been calculated by Nakano (1988, 1997, 2005, 2010), D. K. Yeomans and P. W. Chodas (1989), G. Sitarski (1991), K. Muraoka (1994), and K. Kinoshita (1998, 2003). These calculations included full planetary perturbations and solved for nongravitational effects. The perihelion date was given as June 18.05 and the period was given as 5.10 years. The nongravitational terms were within the following ranges: A1 = 0.00 to +0.01 and A2 = 0.0011. The orbit of Nakano (2005) is given below. T ω Ω (2000.0) i q e 1987 Jun. 18.0461 (TT) 359.3058 213.3355 21.1005 0.993303 0.664713

absolute magnitude: H10 = 12, n = 3.6, from visual observations (Meyer) full moon: 1986 Jul. 21, Aug. 19, Sep. 18, Oct. 17, Nov. 16, Dec. 16, 1987 Jan. 15, Feb. 13, Mar. 15, Apr. 14, May 13, Jun. 11, Jul. 11, Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2, Mar. 3, Apr. 2, May 1, May 31, Jun. 29, Jul. 29, Aug. 27, Sep. 25, Oct. 25, Nov. 23, Dec. 23, 1989 Jan. 21, Feb. 20, Mar. 22, Apr. 21, May 20, Jun. 19, Jul. 18, Aug. 17, Sep. 15, Oct. 14, Nov. 13, Dec. 12, 1990 Jan. 11 sources: S. Nakano, Nakano Note, No. 480 (1985 Jul. 11); S. Nakano, MPC, No. 10519 (1986 Mar. 26); K. Birkle, IAUC, No. 4255 (1986 Sep. 17); K. Birkle, MPC, No. 11210 (1986 Oct. 17); P. A. Wehinger and M. J. S. Belton, IAUC, No. 4311 (1987 Feb. 5); T. Gehrels, J. V. Scotti, P. A. Wehinger, and M. J. S. Belton, MPC, No. 11565 (1987 Feb. 13); J. V. Scotti, MPC, No. 11684 (1987 Apr. 14); J. V. Scotti, MPC, No. 11780 (1987 May 13); E. A. Jacobson, IAUC, No. 4410 (1987 Jun. 15); A. Hale and C. S. Morris, IAUC, No. 4411 225

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(1987 Jun. 25); A. Hale and C. S. Morris, ICQ, 9 (1987 Jul.), p. 118; J. V. Scotti and [Perth], MPC, No. 11892 (1987 Jul. 11); D. A. J. Seargent, C. S. Morris, and A. Hale, IAUC, No. 4421 (1987 Jul. 16); T. Gehrels and J. V. Scotti, MPC, Nos. 12167, 12170 (1987 Sep. 7); A. Hale and C. S. Morris, IAUC, No. 4450 (1987 Sep. 19); A. Hale, C. S. Morris, M. Amoretti, T. Gehrels, and J. V. Scotti, ICQ, 9 (1987 Oct.), p. 168; T. Gehrels and J. V. Scotti, MPC, No. 12361 (1987 Nov. 5); E. A. Jacobson and R. J. Bouma, ICQ, 10 (1988 Jan.), p. 23; A. Hale, ICQ, 10 (1988 Apr.), p. 51; [Calar Alto], MPC, No. 13004 (1988 May 1); A. C. Gilmore, MPC, No. 13358 (1988 Aug. 27); S. Nakano, Nakano Note, No. 527 (1988 Nov. 3); K. J. Meech, MPC, No. 13782 (1988 Nov. 23); D. K. Yeomans and P. W. Chodas, AJ, 98 (1989 Sep.), pp. 1083–93; G. Sitarski, AcA, 41 (1991), pp. 237–53; K. J. Meech, MPC, Nos. 19066, 19071 (1991 Nov. 21); K. J. Meech correspondence with G. W. Kronk (1994); K. Muraoka, Nakano Note, No. 611 (1994 Apr. 21); S. Nakano, Nakano Note, No. 700 (1997 Dec. 12); K. Kinoshita correspondence with G. W. Kronk (1998, 2003); S. Nakano, Nakano Note, No. 1193 (2005 Jul. 4); S. Nakano, Nakano Note, No. 1908 (2010 Apr. 8). 156P/1986 R1 Discovered: 1986 September 3.64 (Δ = 0.93 AU, r = 1.84 AU, Elong. = 143
) (Russell– Last seen: 1986 September 25.65 (Δ = 0.81 AU, r = 1.74 AU, Elong. = 148
) LINEAR) Closest to the Earth: 1986 October 14 (0.7782 AU) Calculated path: SCL (Disc) [Did not leave this constellation] During September 1986, K. S. Russell (Siding Spring Observatory, New South Wales, Australia) located the diffuse trail of a comet on a photographic plate exposed by F. G. Watson during 1986 September 3.64–3.71. The plate was a 90-minute exposure obtained using the 122-cm Schmidt telescope. The magnitude was estimated as 17, while the position was α = 0h 47.8m, δ = 32
230 (2000). M. Hartley (Siding Spring Observatory) obtained a 30-minute follow-up exposure using the same telescope during September 25.63–25.65, but neither Russell nor R. H. McNaught could locate the comet. It was considered lost. During 2000, the Lincoln Laboratory Near-Earth Asteroid Research (LINEAR) project (New Mexico, USA) discovered an asteroidal object, which T. B. Spahr linked to an asteroidal object discovered at Palomar Observatory (California, USA) during 1993. The object was then linked to the comet found by Russell in 1986. With a multi-apparition orbit now available, McNaught and M. A. Read re-examined the plate that had been exposed by Hartley and found the comet. The position at the end of that exposure was α = 0h 27.4m, δ = 31
070 (2000). The comet had attained its most southerly declination of 32
on September 7 and it reached a maximum elongation of 148
on September 23. B. G. Marsden (2003), S. Nakano (2003, 2011), and K. Kinoshita (2003, 2007) calculated multiple-apparition orbits. These calculations included full planetary perturbations. The result was a perihelion date of 1986 226

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December 4.80–4.81 and a period of 6.84 years. The orbit of Kinoshita (2007) is given below. T ω Ω (2000.0) i q e 1986 Dec. 4.8045 (TT) 357.7270 39.0550 20.7524 1.595495 0.557262

absolute magnitude: H10 = 14.5 (Kronk, based on one magnitude estimate) full moon: Aug. 19, Sep. 18, Oct. 17 sources: K. Kinoshita correspondence with G. W. Kronk (2003, 2007); K. S. Russell, F. G. Watson, M. Hartley, R. H. McNaught, [LINEAR], [Palomar], T. B. Spahr, M. E. Read, and B. G. Marsden, IAUC, No. 8118 (2003 Apr. 19); S. Nakano, Nakano Note, No. 948 (2003 Apr. 24); R. H. McNaught and M. Hartley, MPC, No. 48375 (2003 May 1); S. Nakano, Nakano Note, No. 2140 (2011 Oct. 31). 113P/Spitaler Recovered: 1986 September 30.39 (Δ = 1.39 AU, r = 2.22 AU, Elong. = 137
) Last seen: 1986 September 30.46 (Δ = 1.39 AU, r = 2.22 AU, Elong. = 137
) Closest to the Earth: 1986 November 13 (1.1631 AU) Calculated path: ARI (Rec) [Did not leave this constellation] This comet was originally discovered on 1890 November 17 by R. Spitaler (Vienna, Austria) and was last detected on 1891 February 4. Although the comet’s period was determined as about 6.4 years, the comet was not found at the next few predicted apparitions and was considered lost. J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) accidentally rediscovered this comet on 1993 October 24. The Second Palomar Sky Survey (POSSII) was conducted from the early 1980s through 1999 using the 122-cm Schmidt telescope at Palomar Observatory (California, USA). During the survey, the sky was systematically photographed using Kodak IIIa-J (blue), IIIa-F (red), and IVN (near infrared) plates, although not all of these photographic plates were exposed on the same field each night. Numerous comets, minor planets, and supernovae were discovered as astronomers carefully scanned each plate as part of quality control; however, some objects were missed. Such was the case in 1986, when J. E. Mueller (Palomar Observatory) obtained a 100-minute exposure, using a Kodak IIIa-F (red) plate, that began on September 30.39 and ended on September 30.46. An examination did not reveal anything unusual and the photographic plate was accepted as a POSSII plate. Mueller again inspected this particular POSSII plate during 1997 September. The inspection was visual, using a light box, and the purpose was to look for transients. She found a “comet suspect with the tail to the west/southwest.” The magnitude was estimated as 15 and the comet had trailed during the exposure. No other plates were exposed on this region at the time. Mueller (2012) wrote that she was much more experienced at 227

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examining plates in 1997 than in 1986 and she remembers that the comet “just jumped out at me.” The position was α = 3h 08.6m, δ = +20
360 (2000) and the comet was moving very slowly northward. During early 2000, this comet trail was identified as a previous return of 113P/Spitaler. Multiple apparition orbits have been calculated by P. Rocher (1995, 2000, 2001), S. Nakano (1998, 2005), K. Kinoshita (2000, 2001, 2007, 2010), and T. Kobayashi (2012). All of these calculations included full planetary perturbations, while Kobayashi also solved for nongravitational effects. The result was a perihelion date of December 26.55–26.56 and a period of 7.07 years. Kobayashi gave the nongravitational terms as A1 = +0.32 and A2 = +0.0027. The orbit of Kobayashi is given below. T ω Ω (2000.0) i q e 1986 Dec. 26.5610 (TT) 50.0360 14.5984 5.7847 2.122037 0.423956

absolute magnitude: H10 = 10.8 (Meyer) full moon: Sep. 18, Oct. 17 sources: P. Rocher correspondence with G. W. Kronk (1995, 2000, 2001); S. Nakano, Nakano Note, No. 669 (1998 Apr. 29); K. Kinoshita correspondence with G. W. Kronk (2000, 2001, 2007, 2010); J. E. Mueller, MPC, No. 39713 (2000 Apr. 18) ); G. W. Kronk, Cometography, Volume 2, Cambridge (England): Cambridge University Press (2003), pp. 660–2; S. Nakano, Nakano Note, No. 1192 (2005 Jun. 16); J. E. Mueller correspondence with G. W. Kronk (2012); T. Kobayashi, Nakano Note, No. 2296 (2012 Jul. 27). C/1986 V1 Discovered: 1986 November 1.32 (Δ = 1.58 AU, r = 2.37 AU, Elong. = 133
) (Sorrells) Last seen: 1987 September 28.18 (Δ = 3.05 AU, r = 3.02 AU, Elong. = 79
) Closest to the Earth: 1986 November 29 (1.1914 AU) 1987 II=1986n Calculated path: TAU (Disc), ARI (Nov. 25), PSC (Dec. 11), PEG (1987 Jan. 8), EQU (Jun. 28), DEL (Jul. 5), AQL (Jul. 12), SER (Aug. 5), SCT (Aug. 6), SER (Aug. 12), OPH (Aug. 19), SER (Aug. 29), OPH (Aug. 30), SER (Sep. 3) This comet was discovered by W. Sorrells (Pleasanton, California, USA) on 1986 November 1.32. Sorrells was using the 40-cm reflector of the Peninsula Astronomical Society in northern California to photograph the faint supernova remnant S147. He was using Kodak Technical Pan 2415 film that had been hypersensitized to enable it to pick up fainter detail and exposed it for 60 minutes. Sorrells immediately developed the film and noted a diffuse trail a short distance below the faintly visible supernova remnant. The position was α = 5h 42.0m, δ = +26
520 (2000). Suspecting it was a comet, he drove to Foothill College Observatory (near San Jose, California) where he used the 41-cm reflector to visually observe the comet. He also acquired a 10-minute exposure on November 1.49. He estimated the magnitude as 12.5 and described the comet as a “somewhat starlike image surrounded by diffuseness.” 228

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Several observers confirmed the discovery on November 2. A. Young (Burwash, England) estimated the magnitude as 12 on November 2.00. He noted the comet was diffuse, with condensation. He then obtained photographs on November 2.04 and November 2.05. B. Manning (Stakenbridge, England) obtained photographs on November 2.05 and November 2.06, estimating the magnitude as 11 and describing the comet as diffuse, with condensation. Two photographs were acquired by S. Ueda (Kushiro, Hokkaido, Japan) on November 2.65 and November 2.67 using a 16-cm reflector. H. Kaneda (Sapporo, Hokkaido, Japan) obtained two photographs using a 25-cm reflector on November 2.68 and November 2.73. He estimated the magnitude as 12. K. Watanabe (Sapporo Science Center) photographed the comet using the 60-cm reflector on November 2.69, November 2.71, and November 2.73. He estimated the magnitude as 12.0. The comet was well observed during the remainder of November. D. E. Machholz (San Jose, California, USA) saw the comet using his 25-cm reflector on the 3rd and estimated the magnitude as 12. On the 4th, the magnitude was given as 11.2 by A. Hale (Las Cruces, New Mexico, USA) and C. S. Morris (near Mt. Wilson, California, USA), and 11.7 by J. Kobayashi (Kumamoto, Kumamoto, Japan). Observing with a 26-cm reflector on the 6th, G. M. Hurst (Basingstoke, England) determined the magnitude as 11.7. Machholz judged the magnitude as 10.9 on the 12th. After having moved northward since discovery, the comet attained a declination of +29
on November 19 and then began a southerly motion. Kobayashi saw the comet on the 21st and 22nd. For the first date, he gave the magnitude as 10.5 and noted a tail extending 30 toward PA 180
. On the second night, he gave the magnitude as 10.4 and said the tail extended 50 in PA 175
. The comet reached a maximum elongation of 171
on November 22. J.-C. Merlin (Le Creusot, France) saw the comet with a 15-cm reflector on the 27th and determined the magnitude as 9.6. The two most prolific observers during December were R. J. Bouma (Netherlands) and G. Comello (Netherlands). Bouma saw the comet on 13 nights using a variety of instruments ranging from 10  50 binoculars to a 25-cm reflector and reported a fairly steady increase in brightness from magnitude 9.3 on the 2nd to 8.8 on the 31st. He said it remained moderately condensed in the 25-cm reflector, but was described as slightly condensed in the binoculars. Bouma noted the coma diameter as 20 on the 3rd and 6th, 50 on the 28th, and 60 on the 29th. Comello saw the comet on 11 nights spanning the 3rd to the 31st using his 20-cm reflector. He reported the magnitude steadily brightened from about 10.3 to 9.1. The coma varied from slightly to moderately condensed, being 20 across on the 8th and about 10 across on the 21st and 23rd. Comello also noted a tail 1.5–20 long on the 3rd, 21st, and 22nd. On the latter two dates, he said the tail extended toward PA 80
. Many other observers followed the comet during December. C. E. Spratt (Victoria, British Columbia, Canada) observed the comet using his 20-cm reflector on the 1st and gave the magnitude as 9.7. On the 229

cometography: a catalog of comets

6th, J. E. Bortle (Stormville, New York, USA) gave the magnitude as 9.7, using 20  80 binoculars. He added that the coma was slightly condensed and 50 across. M. V. Zanotta (near Como, Italy) saw the comet on the 22nd using 10  50 binoculars. He gave the magnitude as 8.3 and noted a slightly condensed coma 100 across. Also on the 22nd, Morris (Whitaker Peak, California, USA) gave the magnitude as 8.6 and reported a moderately condensed coma 4.70 across. J. DeYoung (Sterling, Virginia, USA) saw the comet using his 25-cm reflector on the 31st and gave the magnitude as 9.3. The comet continued to be well observed during 1987 January, with A. Ishikawa (Japan) and M. Möller (Germany) being the most prolific observers. Ishikawa saw the comet on 11 nights spanning the 1st to the 26th, using 13-cm and 20-cm reflectors. His magnitudes ranged from 9.3 to 9.8, with a slight fading indicated. Möller saw the comet on nine nights spanning the 2nd to the 31st, mostly using his 15-cm reflector. He reported the magnitude generally faded from 9.6 to about 10.6. Both reported the coma varied from slightly to moderately condensed. Ishikawa said the coma diameter ranged from 20 to 3.50 , while Möller said it varied from 10 to 30 . Many other observers followed the comet and reported a tail. Hale noted a tail extending 50 toward PA 40
on the 2nd and 80 toward PA 60
on the 19th and 22nd. R. L. van der Weg (Netherlands) saw the comet on the 28th using his 21-cm reflector and said the tail extended 3.50 toward PA 60
. The comet became more of a challenge to observe during February as the elongation from the Sun decreased from 51
to 23
. Observers typically described the coma as moderately condensed. On the 1st, Morris (Lockwood Valley, California, USA) and Zanotta gave the magnitude as 9.1 and 9.2, respectively. Morris said the coma was 3.10 across, while Zanotta estimated it as 50 across. Hale and Morris independently saw the comet on the 2nd, giving the magnitude as 9.4 and 9.1, respectively. Morris said the coma was 2.60 across. Moonlight began interfering thereafter, although Möller did manage to see the comet using his 15-cm reflector on the 7th. He gave the magnitude as 10.6 and said the coma was 1.20 across. After moonlight ceased to be a problem, Hale observed the comet on the 16th and estimated the magnitude as 9.4. On the 18th, Morris (Whitaker Peak, California, USA) gave the magnitude as 8.9 and reported the coma diameter as 3.10 . Zanotta saw the comet on the 23rd using a 25-cm reflector and judged the magnitude as 9.3. He said the coma was 40 across. The final observation made before the comet became lost in the Sun’s glare came on the 28th, when Hale estimated the magnitude as 9.5. No observations were made during March, as the comet passed only 12
from the Sun on the 19th. After having moved southward since last November, the comet attained a declination of +10
on March 3 and then began a northerly motion. Only a few observations were made during April as the comet exited twilight, entering the morning sky. Hale saw the comet using his 20-cm reflector on the 11th, giving the magnitude as 10.0. A further observation by 230

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Hale on the 23rd revealed the comet had brightened to magnitude 9.8. A. Nakamura (Kuma, Ehime, Japan) saw the comet on the 24th, using his 20-cm reflector. He gave the magnitude as 9.7 and noted a moderately condensed coma 3.50 across. Nakamura, Kobayashi, and A. Ishikawa (Japan) independently saw the comet on the 29th. Nakamura gave the magnitude as 9.7 and reported a slightly condensed coma 40 across. Kobayashi gave the magnitude as 9.2. Ishikawa was using his 13-cm reflector and gave the magnitude as 9.4. He said the coma was slightly condensed and 30 across. Morris saw the comet on the 30th, giving the magnitude as 10.1. He noted a moderately condensed coma 3.00 in diameter. The most prolific observer of this comet during May was A. F. A. L. Jones (New Zealand), who saw the comet on 10 nights. Using his 32-cm reflector, he noted that the magnitude generally faded from 10.9 to 11.3, while the coma exhibited very little condensation and remained about 10 across. Many other observers followed the comet using smaller telescopes and reported a brighter magnitude. Using a 21-cm reflector on the 1st, G. W. Wolf (Wellington, New Zealand) determined the magnitude as 9.5. Nakamura gave the magnitude as 9.8 and 9.5 on the 7th and 9th, respectively. He added that the coma was moderately condensed and 3–40 across. Hale gave the magnitude as 9.7 on the 5th. A. J. S. Pereira (Linda-A-Velha, Portugal) used a 15-cm reflector on the 12th and gave the magnitude as 9.8. Nakamura gave the magnitude as 9.7 on the 24th and said the moderately condensed coma was 3.50 across. After having moved northward since early March, the comet attained a declination of +13
on May 27 and then began a southerly motion. That same night, Hale gave the magnitude as 9.9, using his 41-cm reflector. On the 30th, Morris (near Mt. Wilson, California, USA) determined the magnitude as 10.1, using his 26-cm reflector. With the comet’s distances from the Sun and Earth still increasing and decreasing, respectively, the brightness changed little during June. Jones was once again the most prolific observer. Using his 32-cm reflector, he reported magnitudes that varied from 11.0 to 11.3 during the 1st to the 20th. He then reported a magnitude of 11.6 on the 30th. During the entire month, he noted a slightly condensed coma that was 1–20 across. Observers using smaller telescopes with wider fields of view reported brighter magnitudes. Using a 20-cm reflector on the 1st, Hale gave the magnitude as 9.9. Nakamura was also using a 20-cm reflector on the 6th, when he judged the magnitude as 9.3. He also noted a moderately condensed coma 4.50 across. Nakamura gave the magnitude as 9.4 on the 20th and indicated the coma was unchanged in appearance. On the 21st, the comet was independently seen by Zanotta (Milan, Italy), Morris, and Nakamura, who gave magnitudes of 9.5, 9.7, and 9.7, respectively. All three observers noted a moderately condensed coma and indicated the diameter was 4–50 across. The same three observers again saw the comet on the 27th. Morris gave the magnitude as 9.8 and said the comet was moderately condensed and 2.70 across. He added that his 26-cm reflector revealed a tail extending 2.50 231

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toward PA 90
. Nakamura gave the magnitude as 10.0, noting a slightly condensed coma 40 across. Zanotta said the magnitude was 9.6 and reported a moderately condensed coma 60 across. Geometric conditions involving the Earth, Sun, and comet changed on July 12. The comet had been moving away from the Sun since March 9 and moving toward Earth since March 22. But after Earth passed 1.41 AU from the comet on July 12, the comet’s distances from both the Sun and Earth were increasing, which resulted in a more rapid fading of the comet. The most prolific observer during July was S. Garro (France), who saw the comet on nine nights spanning the entire month using his 20-cm reflector. He generally noted that the brightness faded from 10.5 to 11.4. He noted a slightly condensed coma on the 4th and 7th that was 1.5–20 across. Also on the 4th, Garro reported a tail extending 80 in PA 152
. Morris saw the comet on five nights spanning the 1st to the 26th. He indicated the magnitude faded from 9.8 to 10.8. A moderately condensed coma was generally noted as 30 across, while a short tail was noted on the 19th and 25th, which extended toward PA 100
. The comet reached a maximum elongation of 157
on July 22. The comet continued to fade during August. Zanotta (near Como, Italy) was one of the most prolific observers. He saw the comet on five nights spanning the 1st to the 18th, using reflectors ranging from 25-cm to 41-cm. The magnitude faded from 10.8 to 11.1, while the coma remained moderately condensed and about 30 across. Hale observed the comet on three nights spanning the 13th to the 28th, indicating the magnitude faded from 11.5 to 12.2. Morris saw the comet on three nights spanning the 16th to the 30th. He noted the magnitude faded from 11.5 to 12.5, while the coma was generally slightly condensed and about 20 across. T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired CCD images on August 31 while using the 91-cm reflector. The magnitude was given as 14.9 and the nuclear magnitude was 16.5. The coma was described as slightly condensed and 6200 across, while a tail extended 3.50 toward PA 90
. No observations were made during the first half of September because of bright moonlight, but the comet was seen during the second half of the month. Visual observations were made by Kobayashi and Morris. Kobayashi saw the comet using his 31-cm reflector on the 18th and gave the magnitude as 13.3, while Morris saw the comet using his 26-cm reflector on the 20th and estimated the magnitude as 13.5. Morris added that the coma appeared uncondensed and about 1.00 across. The final astrometric position was made by M. Tsumura (Oishi, Wakayama, Japan) on September 19.47, when he photographed the comet using a 31-cm reflector. No physical description was provided. The position was α = 17h 30.3m, δ = 13
270 (2000). The comet was last detected during September 28.14–28.18, when A. L. Cochran (McDonald Observatory, Texas, USA) obtained a total exposure of 3200 seconds using the 272-cm reflector and an Intensified Dissector Scanner. She said the coma was 1000 across. 232

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The spectrum of this comet was examined during 1986 November 28–30. S. Wyckoff and S. Tegler (Fred Lawrence Whipple Observatory, Mt. Hopkins, Arizona, USA) used the 447-cm Multiple Mirror Telescope and detected emissions of cyanogen, diatomic carbon, and triatomic carbon. The first parabolic orbit was calculated by B. G. Marsden and was published on 1986 November 5. He used eight positions from November 2–4, and determined the perihelion date as 1987 March 9.88. An improved orbit was published by Marsden on November 16, when he used 43 positions from November 2–12 and determined the perihelion date as March 9.62. An additional revision was published by Marsden on December 16. This used 52 positions from November 2 to December 6 and revealed a perihelion date of March 9.66. The first elliptical orbit was published by Marsden on 1987 February 13. He used 98 positions from 1986 November 2 to 1987 January 24, giving a perihelion date of March 9.76 and a period of about 39 thousand years. As additional observations were reported, revised orbits were calculated by Marsden and T. Kobayashi as 1987 progressed. Marsden used 100 positions from 1986 November 2 to 1987 May 7 and included perturbations by all nine planets. The result was a perihelion date of March 9.68 and a period of about 292 thousand years. Kobayashi took 224 positions from 1986 November 2 to 1987 August 26 and included perturbations by all nine planets. The result was a perihelion date of March 9.65 and a period of about 2.7 million years. The only orbit that was calculated using positions spanning the entire period of visibility was published by S. Nakano (1992). He took 270 positions and included perturbations by all nine planets. The result was a perihelion date of March 9.65 and a period of about 2.6 million years. T ω Ω (2000.0) i q e 1987 Mar. 9.6545 (TT) 70.2329 74.8046 160.5801 1.721155 0.999909

absolute magnitude: H0 = 3.8, n = 6.7 (Kronk) full moon: 1986 Oct. 17, Nov. 16, Dec. 16, 1987 Jan. 15, Feb. 13, Mar. 15, Apr. 14, May 13, Jun. 11, Jul. 11, Aug. 9, Sep. 7, Oct. 7 sources: W. Sorrells, A. Young, and B. Manning, IAUC, No. 4267 (1986 Nov. 3); H. Kaneda, K. Watanabe, B. Manning, B. G. Marsden, D. E. Machholz, A. Hale, and C. S. Morris, IAUC, No. 4268 (1986 Nov. 5); A. Young, B. Manning, S. Ueda, H. Kaneda, K. Watanabe, and B. G. Marsden, MPC, Nos. 11279, 11340 (1986 Nov. 16); J. Kobayashi, G. M. Hurst, and D. E. Machholz, IAUC, No. 4275 (1986 Nov. 25); A. Young and B. G. Marsden, MPC, Nos. 11379, 11429 (1986 Dec. 16); S. Wyckoff and S. Tegler, IAUC, No. 4284 (1986 Dec. 17); J.-C. Merlin, C. E. Spratt, J. E. Bortle, M. V. Zanotta, and C. S. Morris, IAUC, No. 4287 (1986 Dec. 23); W. Sorrells, ST, 73 (1987 Jan.), p. 114; M. V. Zanotta, J. Kobayashi, A. Hale, J. DeYoung, C. E. Spratt, and C. S. Morris, IAUC, No. 4306 (1987 Jan. 28); 233

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B. G. Marsden, MPC, No. 11614 (1987 Feb. 13); J. Kobayashi, and C. S. Morris, IAUC, No. 4325 (1987 Mar. 1); R. J. Bouma, G. Comello, M. Möller, R. L. van der Weg, and C. S. Morris, ICQ, 9 (1987 Apr.), pp. 74–8; C. S. Morris and A. Hale, IAUC, No. 4375 (1987 Apr. 27); B. G. Marsden, MPC, No. 11845 (1987 May 13); J. Kobayashi, G. W. Wolf, A. Hale, and A. J. S. Pereira, IAUC, No. 4396 (1987 May 21); A. Hale, C. S. Morris, and G. W. Wolf, IAUC, No. 4403 (1987 Jun. 4); A. Hale, C. S. Morris, and M. V. Zanotta, ICQ, 9 (1987 Jul.), pp. 115–16; T. Kobayashi, M. V. Zanotta, C. S. Morris, and J. V. Scotti, IAUC, No. 4418 (1987 Jul. 10); J. E. Bortle, J. V. Scotti, C. S. Morris, M. V. Zanotta, and A. Hale, IAUC, No. 4432 (1987 Aug. 13); A. F. A. L. Jones, M. V. Zanotta, C. S. Morris, T. Gehrels, J. V. Scotti, and A. Hale, ICQ, 9 (1987 Oct.), pp. 162–4; A. Hale and C. S. Morris, IAUC, No. 4462 (1987 Oct. 3); T. Gehrels and J. V. Scotti, MPC, Nos. 12255, 12257 (1987 Oct. 7); J. Kobayashi, MPC, No. 12454 (1987 Nov. 5); J. Kobayashi, IAUC, No. 4500 (1987 Nov. 25); C. S. Morris, ICQ, 10 (1988 Jan.), p. 6; S. Garro and M. V. Zanotta, ICQ, 10 (1988 Jul.), pp. 69–70; A. Nakamura and A. Ishikawa, ICQ, 12 (1990 Jul.), pp. 78–80; M. Tsumura and S. Nakano, MPC, Nos. 20369, 20481 (1992 Jul. 14); A. L. Cochran, E. S. Barker, T. F. Ramseyer, and A. D. Storrs, Icarus, 98 (1992 Aug.), pp. 151–62; A. L. Cochran correspondence with G. W. Kronk (2012). 112P/1986 UD Prediscovery: 1986 October 4.39 (Δ = 0.59 AU, r = 1.55 AU, Elong. = 151
) (Urata–Niijima) Discovered: 1986 October 30.58 (Δ = 0.48 AU, r = 1.47 AU, Elong. = 174
) Last seen: 1987 March 27.17 (Δ = 1.75 AU, r = 1.94 AU, Elong. = 86
) 1986 XVI=1986o Closest to the Earth: 1986 November 2 (0.4792 AU) Calculated path: CET (Pre), ARI (Oct. 19), TRI–PSC (Nov. 8), TRI (Nov. 12), PSC (Nov. 17), AND (Nov. 20), PER (1987 Jan. 6), CAM (Feb. 10), AUR (Mar. 10) In the course of an asteroid survey using a 30-cm reflector, T. Urata and T. Niijima (Ojima, Gunma, Japan) discovered this comet on photographs exposed during 1986 October 30.58–30.62. Niijima had exposed the photographs and Urata examined them. Urata noted a “fast-moving asteroidal object” of magnitude 16 and reported it to the Central Bureau for Astronomical Telegrams (Cambridge, Massachusetts, USA), where it received the asteroidal designation “1986 UD”. The position on the first image was α = 2h 03.2m, δ = +19
070 (2000). The object was confirmed on two images acquired during November 2.54–2.57, when K. Suzuki (Toyota, Aichi, Japan) obtained photographs, which Urata examined. Urata described the object as stellar and magnitude 16. The comet had reached a maximum elongation of 176
on October 27. This object’s cometary nature was discovered by T. Seki (Geisei, Kochi, Japan). Using his 60-cm reflector, he photographed the comet on November 3.66 and November 3.67, and reported a “very faint and diffuse coma surrounding a central condensation.” Seki estimated the magnitude as 17. 234

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An additional photograph on November 4.65 also revealed the coma, with Seki estimating the magnitude as 16. M. Lovas (Konkoly Observatory, Piszkesteto Mountain Station, Hungary) independently discovered this comet on November 4.03. He described it as “asteroidal, surrounded by a faint asymmetric coma” and the magnitude was given as 16.0. Two prediscovery images were found. P. Jensen (Brorfelde Observatory, Holbaek, Denmark) noted that the object should have passed through the field of view of the 45-cm Schmidt telescope during an exposure by K. Augustesen on October 29.93. Upon examination of the photograph, Jensen noted a “very weak, trailed” image in the proper location and moving at the expected rate of motion. In 1987 August, S. Nakano reported that minor planet 1986 TD4, which was discovered by E. F. Helin (Palomar Observatory, California, USA), was actually this comet. Helin had found the object on a routine survey plate that had been exposed during October 4.39–4.44 using the 122-cm Schmidt telescope. She had estimated the magnitude as 18.5. The position on the first image was α = 2h 37.4m, δ = +1
260 (2000). Several observatories followed the comet during the remainder of November, but only a few provided physical descriptions. M. Koishikawa (Sendai Observatory, Miyagi, Japan) photographed the comet on November 6 using a 25-cm reflector and estimated the magnitude as 15.5. Seki estimated the photographic magnitude as 16.5 on the 7th. Lovas gave the photographic magnitude as 16.0 on the 8th. T. Kojima (Hoshikawa, Kanagawa, Japan) photographed the comet using a 25-cm reflector and estimated the magnitude as 16. Urata estimated the photographic magnitude as 16 on the 26th. A photograph by S. Ueda (Kushiro, Hokkaido, Japan) on November 26, using a 16-cm reflector, revealed a magnitude of 15.5. A testament to the asteroidal appearance of this comet was again demonstrated in late November. J. Ciffréo and J.-L. Heudier (Centre d’études et de Recherches en Géodynamique et Astrométrie, Caussols, France) had photographed the area using the 90-cm Schmidt telescope on November 27. The stellar trail of a minor planet was noted and reported to the Minor Planet Center, where it was designated “1986 WP5.” During August of 1987, Nakano identified this object as comet Urata–Niijima. Only three physical descriptions were provided during December. J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired CCD images on the 1st using the 91-cm reflector. He determined the magnitude as 15.9. Niijima and Urata estimated the photographic magnitude as 16 on the 20th. T. Gehrels and Scotti estimated the photographic magnitude as 16 on December 29. Observations continued during the first three months of 1987, but only three physical descriptions were provided. The first observations of the year came from Niijima and Urata, when photographs on January 1 235

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revealed a magnitude of 16.5. After having moved northward since its discovery, the comet attained a declination of +54
on 1987 February 16 and then began a southerly motion. Scotti’s images of March 2 revealed a magnitude of 18.5 and a coma 1400 across. The comet was last detected during March 27.14–27.17, when Gehrels acquired three CCD images using the 91-cm reflector. The position on the last image was α = 6h 06.8m, δ = +50
360 (2000). He estimated the magnitude as 19.5 and noted the image was diffuse, with slight condensation. The spectrum of this comet was examined during 1986 November 28–30. S. Wyckoff and S. Tegler (Fred Lawrence Whipple Observatory, Mt. Hopkins, Arizona, USA) used the 447-cm Multiple Mirror Telescope and detected emissions of cyanogen, diatomic carbon, and triatomic carbon. The first parabolic orbit was calculated by B. G. Marsden and was published on 1986 November 5. He used nine positions from October 30 to November 4 and determined the perihelion date as 1986 November 20.47. The first elliptical orbit was calculated by Marsden and was published on November 16. This used 21 positions from October 29 to November 7, giving the perihelion date as November 23.13 and the period as 6.42 years. Marsden published a revision on 1987 April 14. This used 64 positions from 1986 October 29 to 1987 March 2. The result was a perihelion date of November 22.94 and a period of 6.62 years. The first orbit to use positions spanning the entire period of visibility was calculated by S. Nakano and was published on 1987 August 9. This used 71 positions and included perturbations by all nine planets. He determined the perihelion date as November 22.94 and the period as 6.62 years. Multiple apparition orbits have been calculated by Marsden (1994), P. Rocher (1995, 2000, 2007), Nakano (1996, 2003, 2006, 2010), and K. Kinoshita (1999, 2006). All of these calculations included full planetary perturbations, while Rocher’s 2000 work and the calculations published from 2006 onward also solved for nongravitational effects. The result was a perihelion date of November 22.94 and a period of 6.62 years. Rocher (2000) gave nongravitational terms of A1 = +0.37 and A2 = +0.0056. The nongravitational terms from the orbits published from 2006 onward were within the following ranges: A1 = +0.00 to +0.05 and A2 = +0.0050 to +0.0058. The orbit of Nakano (2010) is given below. T ω Ω (2000.0) i q e 1986 Nov. 22.9401 (TT) 21.3945 31.9733 24.2563 1.449207 0.589125

absolute magnitude: H10 = 15.8 (Kronk) full moon: 1986 Sep. 18, Oct. 17, Nov. 16, Dec. 16, 1987 Jan. 15, Feb. 13, Mar. 15, Apr. 14 sources: T. Urata and T. Niijima, IAUC, No. 4267 (1986 Nov. 3); T. Seki, T. Urata, T. Niijima, K. Suzuki, and B. G. Marsden, IAUC, No. 4269 (1986 Nov. 5); K. Augustesen, P. Jensen, T. Urata, T. Niijima, K. Suzuki, T. Seki, 236

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E. F. Helin, M. Koishikawa, and B. G. Marsden, MPC, Nos. 11280, 11317, 11339 (1986 Nov. 16); M. Lovas and B. G. Marsden, IAUC, No. 4270 (1986 Nov. 17); M. Lovas, T. Seki, and T. Urata, MPC, No. 11380 (1986 Dec. 16); S. Wyckoff and S. Tegler, IAUC, No. 4284 (1986 Dec. 17); S. Ueda, J. V. Scotti, T. Niijima, and T. Urata, MPC, No. 11471 (1987 Jan. 15); J. Ciffréo, J.-L. Heudier, T. Gehrels, J. V. Scotti, T. Niijima, and T. Urata, MPC, No. 11573 (1987 Feb. 13); T. Kojima, J. V. Scotti, and B. G. Marsden, MPC, Nos. 11685, 11687, 11738 (1987 Apr. 14); T. Gehrels, MPC, Nos. 11781, 11783 (1987 May 13); J. V. Scotti, ICQ, 9 (1987 Jul.), p. 124; S. Nakano, MPC, No. 12128 (1987 Aug. 9); S. Nakano, Nakano Note, No. 498 (1987 Aug. 20); B. G. Marsden, CCO, 9th ed. (1994), pp. 34, 69; P. Rocher correspondence with G. W. Kronk (1995, 2000, 2007); S. Nakano, Nakano Note, No. 649 (1996 Nov. 8); K. Kinoshita correspondence with G. W. Kronk (1999, 2006); S. Nakano, Nakano Note, No. 941 (2003 Apr. 20); S. Nakano, Nakano Note, No. 1409 (2006 Dec. 6); J. V. Scotti correspondence with G. W. Kronk (2008); S. Nakano, Nakano Note, No. 1906 (2010 Apr. 8); J.-L. Heudier correspondence with G. W. Kronk (2012). 184P/1986 W1 Discovered: 1986 November 28.95 (Δ = 0.84 AU, r = 1.73 AU, Elong. = 144
) (Lovas 2) Last seen: 1987 March 3.16 (Δ = 2.31 AU, r = 2.33 AU, Elong. = 79
) Closest to the Earth: 1986 September 27 (0.5161 AU) 1986 XIII=1986p Calculated path: ARI (Disc), TAU (1987 Feb. 13), ARI (Feb. 14), TAU (Feb. 16) M. Lovas (Konkoly Observatory, Piszkesteto Mountain Station, Hungary) discovered this comet on photographic plates exposed on 1986 November 28.95 and November 30.94 using the 60-cm Schmidt telescope. He gave the magnitude as 14 and described the comet as diffuse, with condensation or nucleus, and exhibiting a short tail. For the first date, the position was α = 1h 49.5m, δ = +14
030 (2000). Several observatories followed the comet during the first week of December. G. Schwartz (Oak Ridge Observatory, Massachusetts, USA) obtained an 11-minute exposure of the comet on the 2nd using the 155-cm reflector, despite a very poor sky, and estimated the magnitude as 16. On the 3rd, photographs by Lovas and T. Seki (Geisei, Kochi, Japan) revealed magnitudes of 14 and 16, respectively. The comet was detected by H. Mori (Hoshikawa, Kanagawa, Japan), B. A. Skiff (Lowell Observatory, Anderson Mesa Station, Arizona, USA), J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA), and Seki on the 4th. Mori’s photograph revealed a magnitude of 14. Skiff’s photograph revealed the comet was rather diffuse, with a magnitude of 14.5. Scotti used the 91-cm reflector and a CCD and estimated the magnitude as 15. Seki’s photograph revealed a “very diffuse” comet of magnitude 15.5. Photographs were obtained on the 5th by C.-Y. Shao (Oak Ridge Observatory), S. Ueda (Kushiro, Hokkaido, Japan), and M. Tsumura (Oishi, Wakayama, Japan). Shao’s 21-minute exposure using the 155-cm reflector revealed a weak image with loose condensation. Ueda and 237

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Tsumura independently estimated the magnitude as 15. On December 7, Seki estimated the photographic magnitude as 16. Moonlight interrupted observations for several days. J. B. Gibson (Palomar Observatory, California, USA) photographed the predicted position of the comet on December 21, using the 152-cm reflector, but no trace was found. Schwartz used the 155-cm reflector to acquire a nine-minute exposure on December 28 and an 18-minute exposure on December 29, but the comet was not detected. These observations prompted B. G. Marsden to suggest that the comet “seems therefore to have faded substantially.” Scotti used the 91-cm reflector and a CCD camera to photograph the comet’s position on 1987 January 3. The comet was found on three images and was described as somewhat diffuse and about 10 across, with a magnitude of 17. Scotti and his colleague, T. Gehrels, acquired additional images of the comet on January 25 and 30. The comet was diffuse and “difficult to measure” on the first date, with a magnitude of 18.5. On the second date, it was described as “very diffuse and uncertain” with a magnitude of 19.5. The comet was last detected during March 1.16–1.19 and March 3.13–3.16, when Gehrels and Scotti acquired pairs of CCD images using the 91-cm reflector. They said the comet’s image appeared “very weak, diffuse and difficult to measure.” They estimated the magnitude as 20 on the 3rd. The position on the last image was α = 3h 54.2m, δ = +20
470 (2000). The first parabolic orbit was calculated by B. G. Marsden and was published on 1986 December 5. He used 11 positions from December 2–5 and gave the perihelion date as 1986 November 9.21. He noted, “A shortperiod elliptical solution is not improbable.” Marsden published a revision on December 30. He wrote, “Departure from parabolic motion is evident, but the size and shape of the short-period orbit are little more than a guess.” His orbit had a perihelion date of 1986 August 29.10 and a period of 6.48 years. Further revised orbits were published by Marsden during the first few months of 1987, which eventually established the perihelion date as September 1.96 and the period as 6.70 years. Orbits using positions spanning the entire period of visibility, excluding Lovas’ positions of November 28 and 30, were published by Marsden, D. W. E. Green (1987), S. Nakano (1997), and K. Kinoshita (1998). These used full planetary perturbations. The result was a perihelion date of September 2.15–2.20 and a period of 6.75–6.77 years. The comet was missed at its 1993 and 2000 apparitions and was considered lost; however, it was rediscovered by R. A. Kowalski (Catalina Sky Survey, Arizona, USA) on 2007 January 9, while acquiring survey images using the 68-cm Schmidt telescope. The positions measured by Kowalski, as well as other astronomers who provided confirming observations on January 9 and 10, revealed this comet was identical to the one found by Lovas in 1986. Multiple apparition orbits have been calculated by Kinoshita (2007) and Nakano (2010). These calculations included full planetary perturbations. 238

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The result was a perihelion date of September 2.26 and a period of 6.78 years. Kinoshita’s orbit is given below. T 1986 Sep. 2.2554 (TT)

ω 71.4058

Ω (2000.0) 283.7485

i q 1.5295 1.458783

e 0.592762

absolute magnitude: H10 = 13.2 (Kronk) full moon: Nov. 16, Dec. 16, 1987 Jan. 15, Feb. 13, Mar. 15 sources: G. Schwartz and C.-Y. Shao, HOPL (1986); M. Lovas, IAUC, No. 4276 (1986 Dec. 1); G. Schwartz, T. Seki, B. A. Skiff, J. V. Scotti, C.-Y. Shao, and B. G. Marsden, IAUC, No. 4279 (1986 Dec. 5); G. Schwartz, T. Seki, B. A. Skiff, J. V. Scotti, H. Mori, and B. G. Marsden, MPC, Nos. 11380, 11428 (1986 Dec. 16); J. B. Gibson, G. Schwartz, M. Lovas, H. Mori, T. Seki, S. Ueda, and B. G. Marsden, IAUC, No. 4291 (1986 Dec. 30); J. V. Scotti and B. G. Marsden, IAUC, No. 4295 (1987 Jan. 8); M. Lovas, T. Seki, S. Ueda, J. V. Scotti, and B. G. Marsden, MPC, Nos. 11471, 11501 (1987 Jan. 15); T. Gehrels, J. V. Scotti, and B. G. Marsden, MPC, Nos. 11566, 11569, 11613 (1987 Feb. 13); H. Mori, T. Gehrels, J. V. Scotti, and B. G. Marsden, MPC, Nos. 11685, 11687, 11737 (1987 Apr. 14); D. W. E. Green, MPC, No. 12124 (1987 Aug. 9); M. Tsumura, MPC, No. 17487 (1991 Jan. 30); S. Nakano, Nakano Note, No. 650 (1997 May 2); K. Kinoshita correspondence with G. W. Kronk (1998); R. A. Kowalski, IAUC, No. 8791 (2007 Jan. 10); S. Nakano, Nakano Note, No. 1912 (2010 Apr. 10). 79P/du Toit– Recovered: 1986 December 27.34 (Δ = 1.19 AU, r = 2.17 AU, Elong. = 171
) Hartley Last seen: 1987 May 25.19 (Δ = 1.16 AU, r = 1.22 AU, Elong. = 68
) Closest to the Earth: 1987 February 2 (1.0370 AU) 1987 IX=1986q Calculated path: GEM (Rec), TAU (1987 Feb. 17), GEM (Feb. 26), CNC (May 5) A prediction for the return of this comet was published by S. Nakano (1986). He used positions of the principal component from the 1982 apparition and included perturbations by all nine planets. The perihelion date was given as 1987 June 14.32. This comet was recovered by J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) on three CCD images acquired during 1986 December 27.34–27.36 using the 91-cm reflector. The magnitude was given as 19.3 and he noted that the comet was “essentially stellar with [a] hint of diffuseness.” The position was α = 7h 00.1m, δ = +25
220 (2000). Three confirming CCD images were acquired during December 28.31–28.35. The comet was only followed by astronomers at Steward Observatory during this apparition. T. Gehrels and Scotti detected the comet on five images acquired on January 3. The nuclear magnitude was given as 18.9. Three more images were obtained on January 25, but no description was provided. Another three images were obtained on both March 27 and 28, at which time the nuclear magnitude was given as 18.7. Three more images 239

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were obtained on May 1, but no descriptive information was provided. During this same period of time, the comet reached a maximum elongation of 177
on January 2 and attained its most northerly declination of +25.5
on January 9. The comet was last detected during May 25.17–25.19, when Gehrels and Scotti acquired three CCD images using the 91-cm reflector. They gave the magnitude as 17.4 and noted a tail extending 1.10 in PA 97
. The position on the final image was α = 8h 54.7m, δ = +14
490 (2000). Multiple apparition orbits have been calculated by G. Forti (1989), Nakano (1999, 2003, 2008), K. Kinoshita (2000, 2008), and B. G. Marsden (2005). These calculations included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of June 14.01 and a period of 5.21 years. The nongravitational terms were within the following ranges: A1 = +0.19 to +0.57 and A2 = +0.0030 to +0.0113. Marsden’s orbit is given below. T ω Ω (2000.0) i q e 1987 Jun. 14.0094 (TT) 251.5610 309.3470 2.9425 1.199061 0.601231

absolute magnitude: H10 = 15.9 (Kronk) full moon: 1986 Dec. 16, 1987 Jan. 15, Feb. 13, Mar. 15, Apr. 14, May 13, Jun. 11 sources: S. Nakano, MPC, No. 10519 (1986 Mar. 26); J. V. Scotti, IAUC, No. 4293 (1987 Jan. 5); J. V. Scotti, MPC, No. 11471 (1987 Jan. 15); T. Gehrels and Scotti, MPC, No. 11685 (1987 Apr. 14); T. Gehrels and J. V. Scotti, MPC, No. 11781 (1987 May 13); T. Gehrels and J. V. Scotti, MPC, Nos. 11893, 11896 (1987 Jul. 11); G. Forti, AAP, 215 (1989), pp. 381–2, 384; S. Nakano, Nakano Note, No. 706 (1999 Nov. 23); K. Kinoshita correspondence with G. W. Kronk (2000, 2008); S. Nakano, Nakano Note, No. 920 (2003 Mar. 17); B. G. Marsden, CCO, 16th ed. (2005), pp. 122–3; S. Nakano, Nakano Note, No. 1579 (2008 Feb. 15). 2P/Encke Recovered: Visible throughout orbit Last seen: Visible throughout orbit 1987 XIII Closest to the Earth: 1987 August 15 (0.8854 AU) Calculated path: CAP (Rec), AQR (Dec. 5), PSC (1986 Mar. 13), AQR (Nov. 3), PSC (Dec. 21), ARI (1987 Apr. 29), TAU (Jun. 2), GEM (Jun. 29), CNC (Jul. 13), LEO (Jul. 23), SEX (Jul. 29), LEO (Aug. 4), CRT (Aug. 9), VIR (Aug. 12), CRV (Aug. 14), VIR (Aug. 20), HYA (Aug. 27), LIB–HYA (Sep. 1), LIB (Sep. 7), SCO (Sep. 15), OPH (Sep. 29), SCO (Oct. 1), OPH (Oct. 4), SGR (Oct. 14), CAP (Dec. 18), AQR (1989 Jan. 1) This comet passed aphelion on 1985 November 21. Almost exactly a month later, S. Nakano (1985, 1986) determined an orbit that took 93 positions from 1970–1985, included full planetary perturbations, and solved for 240

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nongravitational effects. After integrating the comet’s motion to this apparition, he predicted the comet would next pass perihelion on 1987 July 17.40. No observations were attempted near the end of 1985 or during the early months of 1986, as the comet was too close to the Sun. The comet reached a minimum elongation of 1.8
on 1986 March 6. The first observations of the comet were made by K. J. Meech (Kitt Peak National Observatory, Arizona, USA) when she used the 213-cm reflector to acquire two CCD images totaling 600 seconds during 1986 June 3.45–3.47. No description or astrometric positions were provided. The predicted position was α = 0h 11.0m, δ = +4
250 (2000). After having moved northward since the time of aphelion, the comet attained a declination of +7
on July 31 and then began a southerly motion. T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired several CCD images using the 91-cm reflector on August 31. The magnitude was given as 19.5. The position on the first image was α = 23h 57.5m, δ = +5
590 (2000). Astronomers on Kitt Peak provided the only observations during the remainder of 1986. Gehrels and Scotti acquired images on September 1, 2, 25, and 26. The magnitude on the 25th was given as 19.2. Meech acquired images on October 30–31 and November 1–3, measuring magnitudes of 19.62–19.97. D. C. Jewitt and Meech (1987) concluded that these observations indicated the rotation rate of the nucleus was probably 22.43 hours, although periods of 1/2, 1/3, and 2/3 this period “may also satisfy the photometry.” They added, “A low-albedo nucleus is suggested.” The comet reached a maximum elongation of 174
on September 19. After having moved southward since late July, the comet attained a declination of 2
on December 4 and then began a northerly motion. The comet remained too close to the Sun for observations during the first half of 1987. After reaching a minimum elongation of 5
on April 9, the comet reached a maximum elongation of 16
on June 2, and then dropped back to a minimum elongation of only 3
on July 8. After having moved northward since last December, the comet attained a declination of +28
on June 24 and then began a southerly motion. The next observations of this comet came during late July, following its perihelion passage. The first observer was G. W. Wolf (Wellington, New Zealand), who spotted the comet with 7  50 binoculars on the 21st and gave the magnitude as 5.2. Three observers spotted the comet on the 24th: R. H. McNaught (Siding Spring Observatory, New South Wales, Australia), G. J. Garradd (Tamworth, New South Wales, Australia), and A. R. Pearce (Woodlands, Western Australia, Australia). McNaught was using 9  63 binoculars and gave the magnitude as 6.9. Garradd was using his 15-cm reflector and gave the magnitude as 7.1. Both of these observers “thought P/Encke was a uniform disk in bright twilight, but there was clearly a central [condensation] in darker sky.” Garradd added that the coma was 10 across. Pearce was using a 32-cm reflector. He gave the magnitude as 7.6 241

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and reported a moderately condensed coma 1.20 across. He added that the comet was “small and condensed with quite high surface brightness.” The same three observers saw the comet again on the 25th. The magnitude was given as 7.0 by Garradd, 7.3 by McNaught, and 7.7 by Pearce. Garradd and McNaught noted a strongly condensed coma, while Pearce said it was moderately condensed and 10 across. On the 26th, the magnitude was given as 7.1 by Garradd, 7.4 by McNaught, and 7.7 by Pearce. The appearance of the coma was basically unchanged from the previous night. Using a 6-cm refractor, Wolf gave the magnitude as 6.2 on the 28th. D. A. J. Seargent (Australia) saw the comet using his 15  80 binoculars on the 29th and estimated the magnitude as 7.5, while Pearce gave the magnitude as 7.8. Pearce added that the coma appeared moderately condensed and 20 across. On the 30th, T. Lovejoy (Shailer Park, Queensland, Australia) gave the magnitude as 7.7 using 15  80 binoculars. Seargent saw the comet on July 31 and gave the magnitude as 7.7. The comet continued to steadily fade during August. Observations by Seargent and Wolf on the 1st revealed magnitudes of 7.9 and 8.0, respectively, with Seargent reporting a strongly condensed coma about 10 across. M. L. Clark (Australia) saw the comet on six nights spanning the 2nd to the 26th. He used a 31-cm reflector throughout this period and noted the magnitude faded from 7.9 to 10.3. Clark said the coma was moderately condensed and 1.50 across on the 2nd, slightly condensed and 4–50 across from the 13th to the 19th, and uncondensed and 20 across on the 26th. Pearce saw the comet on ten nights during the 2nd to the 28th. Using a variety of telescopes, he noted the comet faded from magnitude 8.6 to 10.4. His 13-cm refractor revealed a coma diameter that was generally between 20 and 40 across. Pearce added that the coma was moderately condensed at the beginning of the month, but was slightly condensed by the 18th. Pearce’s observation on August 28th was the final visual observation of this apparition. No further observations were made during the remainder of 1987. The comet reached a maximum elongation of 70
on September 22. After having moved southward since the latter half of June, the comet attained a declination of 30
on September 30 and then began a northerly motion. The comet was not seen at the beginning of 1988 as it passed only 3
from the Sun on February 7. The first observations of the year were made by Meech (Mauna Kea, Hawaii, USA), when she acquired three CCD images on May 17 and four CCD images on May 18 while using the 224-cm reflector. After having moved northward since last September, the comet attained a declination of 8
on June 15 and then began a southerly motion. Meech (Cerro Tololo Inter-American Observatory, Chile) acquired three CCD images on August 20 while using the 152-cm reflector. The comet reached a maximum elongation of 179
on August 24. J. X. Luu and Jewitt (McGraw-Hill Observatory, Kitt Peak, Arizona, USA) used the 236-cm Ritchey–Chrétien reflector and a CCD camera to obtained photometry of the comet on three nights in September. They said the comet maintained a 242

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stellar appearance and gave R magnitudes of 19.50–19.77 on the 3rd, 19.48–20.08 on the 6th, and 19.45–20.09 on the 7th. They noted the presence of cyclic variations in the comet’s brightness amounting to 0.620.04 magnitude, which they interpreted as indicating the direct observation of an “aspherical rotating nucleus.” They determined the rotation period of the nucleus as 15.08 hours. These observers also noted that the CCD images revealed “a reddened continuum in conjunction with a reflectivity gradient smaller than that of the nucleus of P/Tempel 2.” The comet was last detected in September while Meech was using the 224-cm reflector. She acquired six CCD images during September 9.32–9.36, two CCD images during September 10.37–10.40, two CCD images during September 11.32–11.33, and three CCD images during September 12.35–12.40. The comet appeared stellar on all occasions and the nuclear magnitude was given as 20.0 on the 9th. The position was α = 21h 56.0m, δ = 13
150 (2000) on September 12.39. After having moved southward since mid-June, the comet attained a declination of 15
on October 23 and then began a northerly motion. Meech used the 224-cm reflector at Mauna Kea to acquire three CCD images of the comet’s predicted position during 1988 December 10.23–10.25. Each exposure was 600 seconds in length. Meech (2014) said the comet “was not apparent in a single raw 600s image.” Meech suggested the comet might be visible if the images were stacked, but this was never done. The comet reached a minimum elongation of 1.0
on 1989 March 1 and then passed aphelion on March 8. Multiple apparition orbits have been calculated by Nakano (1987, 1990, 1994), B. G. Marsden (1997), Rocher (2000, 2001, 2003), and K. Kinoshita (2003). These calculations included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of July 17.40 and a period of 3.29 years. Using positions from the apparitions spanning 1974 to 1987, Nakano (1987, 1990) gave nongravitational terms within the following ranges: A1 = +0.02 to +0.04 and A2 = 0.0023. Orbits by Nakano (1994), Marsden (1997), Rocher (2000, 2001, 2003), and Kinoshita (2003) revealed nongravitational terms within the following ranges: A1 = 0.02 to 0.00 and A2 = 0.0018 to 0.0011. T ω Ω (2000.0) i q e 1987 Jul. 17.4011 (TT) 186.2530 334.7405 11.9314 0.331734 0.849891

absolute magnitude: H0 = 10.20, n = 3.37 (V. S. Filonenko and K. I. Churyumov, 1989) full moon: Annual Comet: full moons do not limit the overall period of the comet’s visibility sources: S. Nakano, Nakano Note, No. 485 (1985 Dec. 22); S. Nakano, MPC, No. 10520 (1986 Mar. 26); T. Gehrels and J. V. Scotti, MPC, No. 11110 (1986 243

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Sep. 18); T. Gehrels and J. V. Scotti, MPC, No. 11208 (1986 Oct. 17); T. Gehrels and J. V. Scotti, MPC, No. 11276 (1986 Nov. 16); D. C. Jewitt and K. J. Meech, AJ, 93 (1987 Jun.), pp. 1542–8; T. Gehrels and J. V. Scotti, ICQ, 9 (1987 Jul.), p. 118; G. W. Wolf, G. J. Garradd, and R. H. McNaught, IAUC, No. 4425 (1987 Jul. 24); G. J. Garradd, G. W. Wolf, and T. Lovejoy, IAUC, No. 4447 (1987 Sep. 8); R. H. McNaught, G. J. Garradd, A. R. Pearce, M. L. Clark, and D. A. J. Seargent, ICQ, 9 (1987 Oct.), pp. 146, 168; S. Nakano, Nakano Note, No. 519 (1987 Nov. 14); J. Kobayashi, IAUC, No. 4503 (1987 Nov. 27); K. J. Meech, MPC, No. 13356 (1988 Aug. 27); K. J. Meech, MPC, Nos. 13781, 13783 (1988 Nov. 23); V. S. Filonenko and K. I. Churyumov, KomTs, No. 406 (1989 Sep. 30), pp. 3–4; S. Nakano, Nakano Note, No, 545 (1990 May 20); J. X. Luu and D. C. Jewitt, Icarus, 86 (1990 Jul.), pp. 69–81; K. J. Meech correspondence with G. W. Kronk (1994); S. Nakano, Nakano Note, No. 618 (1994 Apr. 29); B. G. Marsden, CCO, 12th ed. (1997), pp. 46–7; P. Rocher correspondence with G. W. Kronk (2000, 2001, 2003); K. Kinoshita correspondence with G. W. Kronk (2003); A. R. Pearce correspondence with G. W. Kronk (2012); K. J. Meech correspondence with G. W. Kronk (2014). C/1987 A1 (Levy) Discovered: 1987 January 5.55 (Δ = 1.47 AU, r = 0.98 AU, Elong. = 42
) Last seen: 1987 May 24.19 (Δ = 2.13 AU, r = 2.60 AU, Elong. = 106
) 1986 XVII=1987a Closest to the Earth: 1986 October 10 (0.6327 AU) Calculated path: OPH (Disc), LIB (Feb. 24), VIR (Mar. 17), HYA (Mar. 27), CRV (Apr. 3), CRT (Apr. 12), HYA (May 6) In the course of his routine search for comets, D. H. Levy (Tucson, Arizona, USA) discovered this comet on 1987 January 5.55 while using his 41-cm reflector. He had just finished doing some writing and noted the early morning sky was partly cloudy. He initially swept for 40 minutes, but temporarily left to check the computer. When he came back he noted the slight glow of dawn. After two more sweeps, he spotted “a small, faint diffuse glow” that “had the appearance and texture of a comet.” Levy studied the comet for about 45 seconds, estimating the magnitude as 10 and the coma diameter as 30 . He then checked the position in a star atlas, which revealed nothing at that location. Upon returning to the telescope, the object was no longer visible, as “dawn had overpowered its dim light.” Although he indicated a position of α = 17h 19.8m, δ = +11
170 (2000), this was later said to be “substantially in error,” because of twilight and poor seeing. The actual position would have been α = 17h 21.0m, δ = +10
230 (2000). Although the next night was cloudy, he found the comet again on January 7.55 and estimated the magnitude as 11. He said the comet was then slightly condensed and 30 across. Independent confirmations were reported by several observers. W. Kakei (Nihondaira Observatory, Shimizu, Shizuoka, Japan) photographed the comet on January 8.84, using a 13-cm hyperboloid astrocamera, and 244

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estimated the magnitude as 12. T. Furuyama (Tone, Gunma, Japan) photographed the comet during January 8.84–8.85, but provided no physical description. T. Seki (Geisei, Kochi, Japan) photographed the comet on January 8.85–8.86, giving the magnitude as 11. Also, on January 8.86, H. Mori (Japan) photographed the comet using a 25-cm reflector and estimated the magnitude as 13. J. Kobayashi (Kumamoto, Kumamoto, Japan) spotted the comet on January 8.87 using his 31-cm reflector and gave the magnitude as 10.5. C. S. Morris (Little Rock, California, USA) had reported that he saw the comet in twilight on January 8.56 at about magnitude 11, using his 26-cm reflector; however, IAU Circular 4296 reported that this “observation is to be discounted.” The comet was followed by numerous visual observers until moonlight interfered. Levy reported a magnitude of 11.3 on the 9th and noted a very slightly condensed coma. That same night, K. Kanai (Japan) saw the comet using a 15-cm reflector and gave the magnitude as 11.0. He reported a very slightly condensed coma 1.80 across. The same two observers saw the comet again on the 10th, giving the magnitude as 11.0. Levy noted a slightly condensed coma about 30 across, as well as a tail extending about 150 toward PA 315
. Kanai described the coma as slightly condensed and 2.50 across. Levy gave the magnitude as 11.3 on the 11th, noting a slightly condensed coma 20 in diameter. That same night, Morris and A. Hale (Las Cruces, New Mexico, USA) also made observations. Morris gave the magnitude as 10.5 and reported a slightly condensed coma 2.70 across. Hale saw the comet using his 20-cm reflector and gave the magnitude as 10.9. He added that the coma was slightly condensed and 1.50 across. On January 12, the magnitude was given as 11.1 by Levy, 11.3 by G. S. Keitch (Wrington, England), and 11.2 by A. R. Pearce, who was visiting Keitch from Australia. Levy noted a slightly condensed coma 20 across. Keitch and Pearce were both using a 30-cm reflector and noted a slightly condensed coma 1.20 across. No observations were made during January 13–19 because of moonlight. S. Ueda (Kushiro, Hokkaido, Japan) photographed the comet on the 20th, using a 16-cm reflector. Visual observations resumed on the 24th, when A. Nakamura (Kuma, Ehime, Japan) saw the comet with his 20-cm reflector and gave the magnitude as 12.1. He noted a coma 1.20 across. The comet faded during the remainder of the month. The most prolific observer was A. Ishikawa (Japan), who used a 20-cm reflector. During five nights spanning the 25th to the 31st, he reported the magnitude faded from 11.5 to 12.4, while the coma diameter was consistently 20 across. In addition, he indicated the coma showed little condensation. Levy made three observations using his 41-cm reflector. On the 26th, he reported a very slightly condensed coma 2.50 across and a tail extending 1.80 in PA 340
. Levy saw the comet on the 27th and gave the magnitude as 11.5. He added that the coma was about 2.50 in diameter. An observation by Levy on January 29 revealed a magnitude of 12.0 and a coma 20 across. 245

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The comet continued to fade in February as its distance from the Sun increased. It was seen by R. J. Bouma (Netherlands) and Levy on the 1st. Bouma was using his 25-cm reflector. He and Levy both gave the magnitude as 11.9. Bouma said the coma was uncondensed and 1.80 across, while Levy estimated the coma diameter as 2.50 . Levy noted a magnitude of 12.1 on the 2nd, using his 41-cm reflector, and about 13.0 on the 5th, using the 91-cm reflector at Steward Observatory (Arizona, USA). On the latter date, he said the coma was very slightly condensed and 30 across. Morris (Pyramid Lake, California, USA) saw the comet on the 6th, using his 26-cm reflector. He gave the magnitude as 11.2 and noted a very slightly condensed coma 4.00 across. Hale gave the magnitude as 12.0 on the 7th. Following interference from moonlight, J. D. Shanklin (Cambridge, England) observed the comet using a 20-cm refractor on February 25. He gave the magnitude as 13.1 and said the coma was slightly condensed and 10 across. Only a few physical descriptions were provided during March. Levy gave the magnitude as 12.9 on the 3rd and said the coma was very slightly condensed and 20 across. E. A. Jacobson (Evansville, Minnesota, USA) saw the comet using his 25-cm reflector on the 8th and gave the magnitude as 12.7. He said the coma was very slightly condensed and 10 across. T. Gehrels and J. V. Scotti (Steward Observatory) acquired CCD images of the comet on March 27 and 28, using the 91-cm reflector. The nuclear magnitude was given as 18.1 on the first date, while the magnitude was given as 17.6 on the second date. The only observation made during April came on the 3rd, when J. W. Briggs (Chamberlin Observatory field station, Bailey, Colorado, USA) photographed the comet using the 41-cm reflector. He described the comet as “very faint and diffuse” with a coma diameter of 2300 . The comet reached a maximum elongation of 161
on the same date. After having moved southward since its discovery, the comet attained a declination of 24
on April 9 and then began a northerly motion. May was the final month of observations and Gehrels and Scotti were the only observers. They used the 91-cm reflector to acquire CCD images of the comet during May 1.22–1.25, May 2.18–2.21, May 23.17–23.20, and May 24.15–24.19. The magnitude was given as 19.4 on the 2nd and 20.5 on the 24th. Gehrels and Scotti noted the comet appeared “extremely weak” on the 24th and 25th. The position on the final image was α = 10h 42.1m, δ = 21
200 (2000). The first orbit was calculated by B. G. Marsden and was published on 1987 January 12. Marsden used nine positions from January 8–11 and determined a parabolic orbit with a perihelion date of 1986 December 18.31. Marsden calculated revised parabolic orbits that were published through mid-April, which established the perihelion date as December 17.52. Marsden took 33 positions from January 8 to April 3 and included perturbations by all nine planets. He determined a hyperbolic orbit with a perihelion date of December 17.54 and an eccentricity of 1.00079. 246

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D. W. E. Green (1987) took 33 positions from the entire period of visibility and included perturbations by all nine planets. The result was a hyperbolic orbit with a perihelion date of December 17.53 and an eccentricity of 1.00038. This orbit is given below. T ω Ω (2000.0) i q e 1986 Dec. 17.5286 (TT) 95.2451 17.1167 96.5830 0.921485 1.000383

absolute magnitude: H0 = 10.2, n = 5.3 (Kronk) full moon: Dec. 16, 1987 Jan. 15, Feb. 13, Mar. 15, Apr. 14, May 13, Jun. 11 sources: D. H. Levy and C. S. Morris, IAUC, No. 4295 (1987 Jan. 8); W. Kakei, T. Seki, B. A. Skiff, and B. G. Marsden, IAUC, No. 4296 (1987 Jan. 12); W. Kakei, H. Mori, J. Kobayashi, D. H. Levy, A. Hale, C. S. Morris, G. S. Keitch, and A. Pearce, IAUC, No. 4297 (1987 Jan. 15); B. G. Marsden and D. H. Levy, IAUC, No. 4307 (1987 Jan. 30); W. Kakei, T. Seki, and S. Ueda, MPC, No. 11566 (1987 Feb. 13); B. G. Marsden, D. H. Levy, and C. S. Morris, IAUC, No. 4344 (1987 Mar. 14); D. H. Levy, K. Kanai, C. S. Morris, and R. J. Bouma, ICQ, 9 (1987 Apr.), p. 67; T. Furuyama, H. Mori, and T. Seki, MPC, Nos. 11685, 11738 (1987 Apr. 14); D. H. Levy, ST, 73 (1987 May), pp. 546–7; T. Gehrels, J. V. Scotti, J. W. Briggs, and B. G. Marsden, MPC, Nos. 11781, 11783, 11845 (1987 May 13); D. H. Levy, A. Hale, T. Gehrels, and J. V. Scotti, ICQ, 9 (1987 Jul.), p. 112; T. Gehrels and J. V. Scotti, MPC, Nos. 11893, 11896 (1987 Jul. 11); D. W. E. Green, MPC, 12124 (1987 Aug. 9); A. R. Pearce and E. A. Jacobson, ICQ, 9 (1987 Oct.), p. 159; A. Nakamura and A. Ishikawa, ICQ, 12 (1990 Jan.), p. 6; G. S. Keitch, ICQ, 12 (1990 Oct.), p. 124; J. D. Shanklin, ICQ, 15 (1993 Oct.), p. 155. 114P/1986 Y1 Discovered: 1986 December 28.29 (Δ = 0.61 AU, r = 1.55 AU, Elong. = 152
) (Wiseman–Skiff) Last seen: 1987 May 25.17 (Δ = 2.25 AU, r = 2.33 AU, Elong. = 81
) Closest to the Earth: 1986 December 27 (0.6120 AU) 1986 XV=1987b Calculated path: CNC (Disc), CMi (Dec. 31), MON (1987 Jan. 18), HYA (Apr. 6) This comet was found during 1987 January by J. Wiseman on two photographic plates exposed by B. A. Skiff with the 33-cm photographic telescope at Lowell Observatory’s Anderson Mesa Station (Arizona, USA) on 1986 December 28.29 and December 28.34. The magnitude was estimated as 14 and the position on the first plate was α = 8h 06.1m, δ = +8
100 (2000). Skiff and Wiseman were able to confirm the comet on 1987 January 19.11 and January 19.13. The comet had faded to magnitude 14.5. On all occasions, the comet appeared diffuse with a strong condensation. The comet reached a maximum elongation of 160
on January 13. Following the discovery announcement, two groups of astronomers announced that they found the comet on survey photographs. Astronomers of the Yamaneko Group of Comet Observers (YGCO) found it on a 247

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photograph exposed on January 1.64 at the Hoshikawa and Nagano stations (Japan). The magnitude was estimated as 13.5. R. H. McNaught (Siding Spring Observatory, New South Wales, Australia) found a “very weak image” of the comet on a photograph exposed during January 9.59–9.66. Photographs were obtained by H. Mori (YGCO Hoshikawa and Nagano Stations) and T. Seki (Geisei, Kochi, Japan) on January 20. Mori estimated the magnitude as 15.5, while Seki noted a strong condensation. Mori estimated the same magnitude on the 22nd. The first visual observation was also reported on the 22nd, when D. H. Levy (Tucson, Arizona, USA) estimated the magnitude as 14.5 while using his 41-cm reflector. He described the comet as very slightly condensed and 10 across, with a possible tail. Levy saw the comet again on the 23rd and 25th, estimating the magnitude as 14.0. The comet appeared very slightly condensed on both occasions, with Levy giving the coma diameter as 10 on the first date and 0.80 on the second. On the 26th, C. S. Morris (Pyramid Lake, California, USA) saw the comet with his 26-cm reflector and gave the magnitude as 13.3. He said the coma was slightly condensed and 0.80 across. J.-C. Merlin (France) observed the comet using his 40-cm reflector on January 31. He gave the magnitude as 13.8 and reported a strongly condensed coma 0.30 across. Merlin also noted a tail extending about 250 toward PA 262
. Amateur astronomers were no longer following the comet as February began. The first observation of the month came from T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) when they acquired a single CCD image on the 1st using the 91-cm reflector. They estimated the magnitude as 15 and noted a tail extending >9000 in PA 330
. The only other observations reported during February were photographic ones obtained by astronomers at Perth Observatory (Bickley, Western Australia, Australia) during the 2nd, 3rd, 4th, and 5th. No physical descriptions were provided. After having moved southward since its discovery, the comet attained a declination of 4
on February 24 and then began a northerly motion. The comet was only seen from two locations during March. S. J. Bus (Lowell Observatory, Anderson Mesa Station, Arizona, USA) acquired two CCD images of the comet on the 8th, using the 183-cm reflector. No physical description was provided. Gehrels and Scotti acquired several images on the 27th, noting a magnitude of 17.6. After having moved northward since late February, the comet attained a declination of 3
on April 20 and then began a southerly motion. There were no observations made during April, but images were obtained in May by Gehrels and Scotti. They gave the magnitude as 18.6 on the 1st, 18.9 on the 2nd, and 19.0 on the 23rd. The comet was last detected during May 25.16–25.17, when Gehrels and Scotti acquired two CCD images using the 91-cm reflector. They gave the magnitude as 19.4 on the first date and the position as α = 9h 23.3m, δ = 4
140 (2000) on the last. 248

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The first orbit was calculated by B. G. Marsden, using six positions from December 28 to January 21. The comet was shown to move in a shortperiod orbit, with a perihelion date of 1986 November 22.76 and a period of 6.53 years. Marsden commented that the comet passed about 0.25 AU from Jupiter in 1984. S. Nakano (1988) took 38 positions from the entire 1986 apparition and included perturbations by all nine planets. He determined the perihelion date as November 22.76 and the period as 6.52 years. Multiple apparition orbits have been calculated by Marsden (1994, 2001), P. Rocher (1994, 2000, 2001, 2006), S. Nakano (1994, 2003, 2007), and K. Kinoshita (2000, 2009). All of these calculations included full planetary perturbations, while the calculations by Kinoshita (2000, 2009) and Nakano (2007) also solved for nongravitational effects. The perihelion date was given as November 22.76 and the period was 6.52 years. The nongravitational terms were within the following ranges: A1 = +0.28 to +0.50 and A2 = +0.0037 to +0.0060. The orbit of Kinoshita (2009) is given below. T ω Ω (2000.0) i q e 1986 Nov. 22.7611 (TT) 171.7482 271.7219 18.1974 1.505070 0.568632

absolute magnitude: H10 = 13.2 (Kronk) full moon: Dec. 16, 1987 Jan. 15, Feb. 13, Mar. 15, Apr. 14, May 13, Jun. 11 sources: J. Wiseman and B. A. Skiff, IAUC, No. 4299 (1987 Jan. 20); H. Mori, T. Seki, and B. G. Marsden, IAUC, No. 4301 (1987 Jan. 21); D. H. Levy and C. S. Morris, IAUC, No. 4303 (1987 Jan. 26); J. Wiseman, B. A. Skiff, [YGCO Hoshikawa and Nagano stations], and H. Mori, MPC, Nos. 11567, 11569 (1987 Feb. 13); C. S. Morris and J.-C. Merlin, ICQ, 9 (1987 Apr.), p. 80; T. Gehrels, J. V. Scotti, and S. J. Bus, MPC, Nos. 11686–7 (1987 Apr. 14); [Perth], T. Gehrels, and J. V. Scotti, MPC, No. 11781 (1987 May 13); T. Gehrels, J. V. Scotti, and D. H. Levy, ICQ, 9 (1987 Jul.), p. 125; T. Gehrels and J. V. Scotti, MPC, No. 11894 (1987 Jul. 11); R. H. McNaught, MPC, No. 12170 (1987 Sep. 7); S. Nakano, Nakano Note, No. 523 (1988 Nov. 1); P. Rocher correspondence with G. W. Kronk (1994, 2000, 2001, 2006); B. G. Marsden, CCO, 9th ed. (1994), pp. 34, 69; S. Nakano, Nakano Note, No. 598R (1994 Jan. 13); K. Kinoshita correspondence with G. W. Kronk (2000, 2009); B. G. Marsden, CCO, 14th ed. (2001), pp. 94–5; S. Nakano, Nakano Note, No. 939 (2003 Apr. 20); S. Nakano, Nakano Note, No. 1472 (2007 May 4). Discovered: 1987 January 19.48 (Δ = 1.38 AU, r = 1.33 AU, Elong. = 66
) Last seen: 1987 July 17.00 (Δ = 1.88 AU, r = 2.16 AU, Elong. = 92
) Closest to the Earth: 1987 May 27 (0.5500 AU) Calculated path: PSC (Disc), AQR (Mar. 1), CAP (May 6), PsA (May 7), MIC (May 12), SGR (May 18), CrA (May 23), SCO (May 27), NOR (Jun. 1), SCO 1987 III=1987c (Jun. 2), LUP (Jun. 3), CEN (Jun. 8), HYA (Jun. 14), VIR (Jun. 26) C/1987 B1 (Nishikawa– Takamizawa– Tago)

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This comet was independently found by four observers in Japan. N. Nishikawa (Minamata, Kumamoto, Japan) discovered the comet on 1987 January 19.48 while using a 15-cm refractor. He estimated the magnitude as 9 and gave the position as α = 0h 06.8m, δ = +7
090 (2000). K. Takamizawa (Saku, Nagano, Japan) independently discovered this comet on January 20.40. He estimated the magnitude as 9.5 and said the coma was 50 across. A. Tago (Tsuyama, Okayama, Japan) independently discovered the comet on January 20.431 and estimated the magnitude as 9. S. Mitsuma (Honjo, Saitama, Japan) independently discovered the comet on January 20.434 and gave the magnitude as 9. The first confirmations were made on January 20 and 21. J. Kobayashi (Kumamoto, Kumamoto, Japan) saw the comet with a 31-cm reflector on January 20.52. He determined the magnitude as 9.2 and the coma diameter as 60 . M. Koishikawa (Sendai Observatory, Miyagi, Japan) photographed the comet using a 20-cm reflector during January 21.39–21.40. He estimated the magnitude as 9 and noted a diffuse coma 80 across, with a weak central condensation. C.-Y. Shao (Oak Ridge Observatory, Massachusetts, USA) obtained a 17-minute exposure of the comet on January 23.99 using the 41-cm astrograph. He estimated the magnitude as 9 and reported a strong condensation and a short tail toward the northeast. The comet was well followed by Northern Hemisphere observers during the remainder of January. A. Hale (Las Cruces, New Mexico, USA) and C. S. Morris (Mt. Gleason, California, USA) saw the comet on the 22nd. Hale was using a 20-cm reflector and gave the magnitude as 8.1, noting a moderately condensed coma 40 across. Morris was observing with his 26-cm reflector and gave the magnitude as 8.6. He said the coma was very slightly condensed. The comet was also seen by D. H. Levy (Arizona, USA) on the 22nd. He was using his 41-cm reflector, which revealed a fainter magnitude of 8.9. More importantly, he reported a tail extending 0.6
toward PA 25
. On the 24th, Hale gave the magnitude as 8.3. Morris switched to his 20  80 binoculars and also reported the magnitude as 8.3. He added that the coma was very slightly condensed. A. Ishikawa (Japan), who would prove to be one of the most prolific Northern Hemisphere observers of this comet, gave the magnitude as 8.6 while using his 13-cm reflector. He added that the slightly condensed coma was 50 across. During the remainder of the month, Ishikawa reported that the comet generally brightened, with the magnitude being given as 8.2 on the 31st. R. J. Bouma (Netherlands) used a variety of instruments to observe the comet during the 26th to the 31st, noting a general brightening from magnitude 8.2 to 7.9. He noted the coma was slightly to moderately condensed and 4–50 across. Hale noted a tail extending 250 in PA 70
on the 30th. The comet was situated toward the west-southwest in the evening sky as February began, and its elongation was decreasing as it approached perihelion. On the 1st, the magnitude was given as 8.3 by Morris (Lockwood Valley, California, USA), 8.1 by Ishikawa, and 7.9 by A. Nakamura 250

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(Kuma, Ehime, Japan). Morris and Ishikawa, both noted a moderately condensed coma that was 4.40 across and 50 across, respectively. Nakamura also noted a moderately condensed coma, as seen in his 20-cm reflector, and gave the diameter as 5.50 . The number of observers dwindled during the remainder of the month. Ishikawa continued to follow the comet with his 13-cm reflector and noted it brightened to 7.7 by the 15th. During this period, he said the coma was 3–40 across. His last observation on the 16th was made in slight twilight, at which time the magnitude was given as 7.8, while the coma was 20 across. Hale also saw the comet on the 16th and estimated the magnitude as 7.2. Three observers saw the comet on the 17th. Morris was using his 26-cm reflector, noting a magnitude of 7.8, a moderately condensed coma 2.80 across, and a tail extending 200 in PA 25
. W. C. Morrison (Canada) used his 15-cm refractor to determine the magnitude as 8.4. He said the coma was slightly condensed and 30 across. D. E. Machholz (California, USA) saw the comet with his 13-cm refractor and also gave the magnitude as 8.4. He noted a slightly condensed coma that was 40 across. On the 18th, Morris gave the magnitude as 7.8 and reported a moderately condensed coma 2.80 across. The last person to see the comet prior to perihelion was Morrison, who gave the magnitude as 8.3 on February 19. He said the coma was slightly condensed and 30 across. The comet reached a minimum elongation of 0.5
on March 9. The first person to detect it as it was exiting twilight was D. A. J. Seargent (The Entrance, New South Wales, Australia), who spotted it on March 27 using 15  80 binoculars. He determined the magnitude as 6.7 and noted a strongly condensed coma about 1.50 across. Seargent and G. J. Garradd (Tamworth, New South Wales, Australia) independently saw the comet on the 29th. Seargent gave the magnitude as 6.6 and noted a strongly condensed coma. Garradd was using 7  50 binoculars, reporting a magnitude of 7.2 and a coma diameter of 30 . On the 30th, V. F. de Assis Neto (Sao Francisco de Oliveira, Brazil) gave the magnitude as 6.9, using 10  70 binoculars. The comet faded slowly during April and May, as its decreasing distance from Earth countered the increasing distance from the Sun. Observers in the Southern Hemisphere made the majority of the observations, with A. F. A. L. Jones (New Zealand) and Seargent leading the pack. Jones used a variety of instruments while observing the comet during April 11 to May 10, but his 5-cm refractor revealed a slow fading from magnitude 7.1 to 7.7 and a coma that generally grew from 30 to 70 across. His 32-cm reflector revealed a possible tail extending toward PA 255
on May 8 and PA 240
on May 10. Seargent used 15  80 binoculars from April 2 to May 3 and 10  50 binoculars from May 22 to May 29. He indicated that the comet generally faded from magnitude 6.7 to 7.4 during this period. Seargent also provided a series of coma descriptions, noting it was strongly condensed and about 2.50 across on April 10, moderately condensed and 60 across on April 26, 251

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moderately condensed and 70 across on May 3, very slightly condensed and 80 across on May 22, very slightly condensed and 100 across on May 25, and very slightly condensed and 80 across on May 28. He also reported a tail was visible on April 10, which extended about 1
in PA 245
. After having moved southward since its discovery, the comet attained a declination of 45
on May 28 and then began a northerly motion. The comet reached a maximum elongation of 160
on June 2, yet observations were winding down. Garradd saw the comet using 7  50 binoculars on the 1st and gave the magnitude as 7.6. The final astrometric positions were obtained by A. C. Gilmore (Mt. John University Observatory, Lake Tekapo, New Zealand) during June 1.55–1.56. He used a 61-cm reflector and gave the position as α = 16h 32.1m, δ = 42
510 (2000). No descriptions were provided. G. W. Wolf (Wellington, New Zealand) observed with 7  50 binoculars on the 3rd, 7th, and 12th, giving the magnitude as 7.8, 8.0, and 8.3, respectively. Hale saw the comet on the 15th, when his 41-cm reflector revealed a magnitude of 8.8. A. L. Cochran (McDonald Observatory, Texas, USA) acquired a spectroscopic observation during June 25.16–25.22 while using the 272-cm reflector and an Intensified Dissector Scanner. Although no physical description was provided, Cochran detected cyanogen, diatomic carbon, triatomic carbon, methylidyne, and the amidyl radical. Although professional observations ended with Cochran’s observation, the comet continued to be followed by amateur astronomers. G. W. Kronk (Troy, Illinois, USA) saw the comet on June 26, using his 33-cm reflector. He estimated the magnitude as 9.5 and noted a coma 1.50 across. E. A. Jacobson (Evansville, Minnesota, USA) made observations using his 25-cm reflector on June 26, 27, 28, and 30. He gave the magnitude as 9.4 on the first three dates and 9.5 on the last. The coma was described as slightly condensed and 3.10 across on the 27th. Jacobson also used a 29-cm reflector and reported a tail on the 27th and 30th, noting that it extended 20 toward PA 135
on the first night and 30 toward PA 125
on the last night. The final observations of this comet were made by Wolf using his 6-cm refractor. He gave the magnitude as 9.5 on July 1.70, 9.8 on July 10.73, and 10.0 on July 17.00. The predicted position on the final date was α = 13h 23.9m, δ = 17
010 (2000). Early in July, D. I. Olsson-Steel and B. A. Lindblad (Lund Observatory, Sweden) suggested that this comet might be associated with the Epsilon Geminid meteor shower. They said the theoretical radiant for this comet was located at α = 93
, δ = +28
, while Earth’s closest approach (0.05 AU) to the comet’s orbit was occurring on October 7. The actual displacement of the predicted right ascension from the observed right ascension of the Epsilon Geminids was 10 days. In addition, Earth and the comet’s orbit were separated by 0.12 AU on July 21, with the predicted radiant being at α = 35
, δ = +19
. Several observers watched for activity on this night, but no 252

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one saw more than two possible meteors from this radiant during their watch periods, which ranged from 1.1 to 2.7 hours. The first parabolic orbit was calculated by D. W. E. Green and was published on January 23. Using nine positions from January 19–22, he gave the perihelion date as 1987 February 18.03. Additional parabolic orbits were calculated by S. Nakano on January 26 and B. G. Marsden on March 14. Nakano used 14 positions from January 20–25 and determined the perihelion date as March 18.19. Marsden used 21 positions from January 20 to February 19 and determined the perihelion date as March 17.29. The first elliptical orbit was published by Marsden on April 30. He used 51 positions from January 21 to April 29, determining the perihelion date as March 17.34 and the period as about 3214 years. Further calculations by Marsden were published on May 13 and July 11. Although the perihelion date was essentially unchanged, the period was given as about 2483 years for the first orbit and about 2919 years for the second orbit. This last orbit is given below. T ω Ω (2000.0) i q e 1987 Mar. 17.3440 (TT) 200.4017 176.0121 172.2300 0.869579 0.995742

absolute magnitude: H0 = 6.6, n = 4.4 (Kronk) full moon: Jan. 15, Feb. 13, Mar. 15, Apr. 14, May 13, Jun. 11, Jul. 11, Aug. 9 sources: N. Nishikawa, K. Takamizawa, A. Tago, S. Mitsuma, and J. Kobayashi, IAUC, No. 4300 (1987 Jan. 21); N. Nishikawa, M. Koishikawa, C.-Y. Shao, D. W. E. Green, A. Hale, and C. S. Morris, IAUC, No. 4302 (1987 Jan. 23); S. Mitsuma and S. Nakano, IAUC, No. 4304 (1987 Jan. 26); C. S. Morris, IAUC, No. 4326 (1987 Mar. 1); B. G. Marsden, IAUC, No. 4345 (1987 Mar. 14); C. S. Morris and R. J. Bouma, ICQ, 9 (1987 Apr.), p. 78; D. A. J. Seargent and V. F. de Assis Neto, IAUC, No. 4361 (1987 Apr. 8); V. F. de Assis Neto, G. J. Garradd, and D. A. J. Seargent, IAUC, No. 4373 (1987 Apr. 24); B. G. Marsden, IAUC, No. 4380 (1987 Apr. 30); A. Hale, IAUC, No. 4384 (1987 May 5); B. G. Marsden, MPC, No. 11845 (1987 May 13); A. Hale and B. G. Marsden, IAUC, No. 4392 (1987 May 14); A. Hale, IAUC, No. 4402 (1987 Jun. 4); A. Hale, D. H. Levy, and D. A. J. Seargent, ICQ, 9 (1987 Jul.), pp. 116–17; D. I. OlssonSteel, B. A. Lindblad, G. W. Wolf, and A. Hale, IAUC, No. 4414 (1987 Jul. 3); B. G. Marsden, MPC, No. 12009 (1987 Jul. 11); G. W. Wolf, R. H. McNaught, and A. J. S. Pereira, IAUC, No. 4424 (1987 Jul. 24); A. C. Gilmore, MPC, No. 12033 (1987 Aug. 9); W. C. Morrison, G. J. Garradd, and E. A. Jacobson, ICQ, 9 (1987 Oct.), pp. 164–5; D. E. Machholz, ICQ, 11 (1989 Jan.), p. 15; A. Ishikawa and A. Nakamura, ICQ, 12 (1990 Jul.), p. 80; A. L. Cochran, E. S. Barker, T. F. Ramseyer, and A. D. Storrs, Icarus, 98 (1992), pp. 151-62; G. W. Kronk, ICQ, 15 (1993 Jan.), p. 15; A. L. Cochran correspondence with G. W. Kronk (2012); A. L. Cochran, Icarus, 218 (2012 Mar.), pp. 144–68. 253

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C/1987 B2 Discovered: 1987 January 24.40 (Δ = 1.31 AU, r = 0.85 AU, Elong. = 41
) (Terasako) Last seen: 1987 March 6.39 (Δ = 2.05 AU, r = 1.59 AU, Elong. = 49
) Closest to the Earth: 1987 January 12 (1.2561 AU) 1986 XVIII=1987d Calculated path: SCL (Disc), CET (Feb. 2) M. Terasako (Hamamatsu, Shizuoka, Japan) discovered this comet less than 5
from Fomalhaut on 1987 January 24.40. He was using 150-mm binoculars and gave the magnitude as 8. The position was α = 23h 19.0m, δ = 30
160 (2000). Terasako had conducted regular comet-hunting sessions for 1374 hours before finding this comet. He confirmed the discovery on January 25.38 before reporting it to the proper authorities. Independent confirmations were made by S. Mitsuma (Honjo, Saitama, Japan) and H. Shibasaki (Tokyo Astronomical Observatory, Dodaira Station, Saitama, Japan) on January 26.38. They both estimated the magnitude as 8 and described the comet as diffuse with a condensation. News of the comet spread quickly and numerous observations were made during the remainder of January. D. H. Levy (Tucson, Arizona, USA) and J. da S. Campos (Warner Beach, South Africa) saw the comet on the 27th. Levy was using a 20-cm reflector and gave the magnitude as 6.9. He said the coma was moderately condensed and noted a faint sunward tail that extended 100 toward PA 250–270
. Campos said the comet appeared to be magnitude 8.5 in his 13-cm reflector. He added that the coma appeared strongly condensed and 20 across. Also on the 27th, a photograph by T. Seki (Geisei, Kochi, Japan) revealed the coma diameter as 70 . D. A. J. Seargent (The Entrance, New South Wales, Australia) saw the comet with his 15  80 binoculars on the 28th and 29th, giving the magnitude as 7.3 and 7.2, respectively. A. F. A. L. Jones (Nelson, New Zealand) saw the comet using his 11  80 binoculars on the 29th and gave the magnitude as 8.1. He said the coma was 50 across and very slightly condensed. That same night, D. J. Waldron (Siding Spring Observatory, New South Wales, Australia) obtained a 30-minute J exposure which revealed a narrow gas tail extending 1000 in PA 93
and “a dust fan from this point, through p.a. 180
,” increasing in intensity and length to 150 in PA 238
. On the 30th, Levy and A. Hale (Las Cruces, New Mexico, USA) observed with their 20-cm reflectors. Levy gave the magnitude as 6.8 and noted a strongly condensed coma 40 across. He added that a tail extended 100 in PA 65
, while the “sunward feature” extended 100 in PA 260
and appeared “sharper” than on the 27th. Hale said the tail extended 250 toward PA 180
. He added that his 10  50 binoculars revealed the magnitude as 7.3. On January 31, Jones and Seargent gave the magnitude as 7.9 and 7.5, respectively. Jones said the coma was about 5’ across, while Seargent indicated the coma was moderately condensed. The comet was moving away from both the Sun and Earth during February. The most prolific observer during the month was A. Ishikawa (Japan), who saw the comet on eight nights. Using his 13-cm and 20-cm 254

cometography: a catalog of comets

reflectors, he reported that the comet faded from magnitude 7.8 on the 2nd to 8.9 by the 28th. He indicated that the coma remained slightly condensed and varied from 3–50 across. C. S. Morris (Lockwood Valley, California, USA) observed the comet on the 1st using 20  80 binoculars. He gave the magnitude as 7.5 and noted a moderately condensed coma that was 7.50 across. Morris also reported two tails: one extending 500 in PA 78
and the other extending 200 in PA 235
. Morris again noted two tails on the 2nd: one extending 250 in PA 78
and the other extending 200 in PA 220
. Hale also observed on the 2nd, noting a magnitude of 7.6 and reporting a tail extending 250 in PA 180
. On the 6th, Seargent gave the magnitude as 8.3. With some interference from moonlight, G. W. Kronk (Troy, Illinois, USA) and Ishikawa managed to acquire observations on the 8th and 9th. Using his 33-cm reflector, Kronk estimated the magnitude as 9 on both dates, adding that the coma was slightly condensed and 2–30 across. Ishikawa saw the comet on the 8th and gave the magnitude as 8.6. He added that the coma was slightly condensed and 30 across. The comet was at a low altitude in the western sky on February 14 when Ishikawa become the first person to see the comet after the February full Moon, glimpsing the comet during the few minutes between the times it set and the Moon rose. He gave the magnitude as 8.5 and said the coma was slightly condensed and 30 across. J. E. Bortle (Stormville, New York, USA) saw the comet on the 16th, using his 32-cm reflector. He estimated the magnitude as 9.1, noting the coma was very slightly condensed and 3.20 across. Morris observed the comet on the 17th and 18th, using his 26-cm reflector. He gave the magnitude as 8.5 and 8.7, respectively. On the former date, he reported a coma that was slightly condensed and 3.2’ across, while a tail extended 30 in PA 235
. Also on the 18th, Seargent gave the magnitude as 9.1. The comet reached a maximum elongation of 51
on February 21. On the 28th, Hale gave the magnitude as 9.9 and said the coma was very slightly condensed. The comet was continuing to drop into evening twilight as March began. It also continued to fade as it moved away from both the Sun and Earth. Only a few physical descriptions were provided before the comet was lost in twilight. A. Nakamura (Kuma, Ehime, Japan) saw the comet using his 20-cm reflector on the 1st, giving the magnitude as 9.8 and reporting an uncondensed coma 40 across. R. A. Keen (Colorado, USA) saw the comet using his 32-cm reflector on the 2nd. He gave the magnitude as 9.3 and noted a very slightly condensed coma 40 across. Ishikawa observed the comet on the 1st, 2nd, and 3rd. He used his 20-cm reflector on the 1st and gave the magnitude as 9.0. He added that the coma was slightly condensed and 40 across. Ishikawa used his 13-cm reflector on the 2nd and 3rd. The magnitude was given as 9.1 and 9.4, respectively, while the coma was described as slightly condensed and 3.5–40 across. The comet was last detected on March 6.37 and March 6.39, when A. C. Gilmore (Mt. John University Observatory, Lake Tekapo, New Zealand) 255

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acquired photographic exposures of 10.2 and 20 minutes using a 61-cm reflector. No descriptions were provided. The position on the last photograph was α = 2h 25.0m, δ = 7
330 (2000). The first parabolic orbit was calculated by D. W. E. Green, using seven positions from January 26–28, and was published on 1987 January 28. The perihelion date was determined as 1986 December 25.06. Green’s colleague, B. G. Marsden, published an orbit on February 13. This used 23 positions from January 27 to February 3 and revealed a perihelion date of December 24.90. Green published an elliptical orbit on 1987 September 7. He used 25 positions from January 27 to March 5, determining the perihelion date as December 24.87 and the period as about 724 years. This orbit is given below. T ω Ω (2000.0) i q e 1986 Dec. 24.8716 (TT) 195.2764 97.7060 40.8543 0.393020 0.995125

absolute magnitude: H0 = 6.9, n = 2.4 (Kronk) full moon: 1987 Jan. 15, Feb. 13, Mar. 15 sources: M. Terasako, S. Mitsuma, and H. Shibasaki, IAUC, No. 4303 (1987 Jan. 26); H. Shibasaki, T. Seki, D. W. E. Green, and D. H. Levy, IAUC, No. 4305 (1987 Jan. 28); H. Shibasaki, S. Mitsuma, T. Seki, and B. G. Marsden, MPC, Nos. 11568, 11614 (1987 Feb. 13); D. J. Waldron, J. da S. Campos, D. A. J. Seargent, and C. S. Morris, IAUC, No. 4313 (1987 Feb. 18); D. H. Levy, J. da S. Campos, D. A. J. Seargent, C. S. Morris, R. A. Keen, and J. E. Bortle, ICQ, 9 (1987 Apr.), pp. 67–8; M. Terasako, ST, 73 (1987 Apr.), p. 457; D. H. Levy and A. Hale, ICQ, 9 (1987 Jul.), pp. 102, 112–13; D. W. E. Green, MPC, No. 12200 (1987 Sep. 7); A. F. A. L. Jones, ICQ, 9 (1987 Oct.), pp. 146, 159; A. C. Gilmore, MPC, No. 12856 (1988 Apr. 2); A. Nakamura, ICQ, 12 (1990 Jul.), p. 78; A. Ishikawa, ICQ, 13 (1991 Jan.), p. 14; G. W. Kronk, ICQ, 15 (1993 Jan.), p. 15; P. M. Kilmartin correspondence with G. W. Kronk (2011). 86P/1987 B3 Recovered: 1987 January 29.46 (Δ = 2.38 AU, r = 2.69 AU, Elong. = 98
) (Wild 3) Last seen: 1988 September 11.46 (Δ = 2.30 AU, r = 3.26 AU, Elong. = 158
) Closest to the Earth: 1987 May 3 (1.4653 AU) 1987 XX=1987e Calculated path: VIR (Rec), LIB (Aug. 2), SCO (Sep. 27), OPH (Oct. 15), SCO (Oct. 17), OPH (Oct. 29), SGR (Nov. 21), CAP (1988 Jan. 31), PsA–CAP (Mar. 1), AQR (Mar. 18), CET (Jun. 11), AQR (Sep. 7), SCL (Sep. 10) A prediction for the return of this comet was published by S. Nakano (1983, 1986). He took 33 positions from the 1980 discovery apparition and included perturbations by all nine planets. He then integrated the comet’s motion to this apparition and gave the predicted perihelion date as 1987 August 31.26. 256

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This comet was recovered by T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) when they acquired two CCD images using the 91-cm reflector during 1987 January 29.46–29.52. On the first date, the magnitude was given as 19.5, while the position was α = 14h 18.5m, δ = +2
490 (2000). They noted a diffuse coma 1400 across. Three confirming images were acquired by Gehrels and Scotti during February 1.46–1.48. They said the coma was 1600 across. The comet moved slightly southward following its recovery and finally began a northward motion after attaining a declination of +2.7
on 1987 February 12. Gehrels and Scotti acquired three images of the comet on February 28 and gave the magnitude as 19.5. They obtained two more images on March 2. After having moved northward since mid-February, the comet attained a declination of +4
on April 18 and then began a southerly motion. The comet reached a maximum elongation of 163
on April 23. J. W. Briggs (Chamberlin Observatory field station, Bailey, Colorado, USA) photographed the comet with the 41-cm reflector on June 22 and described its appearance as “weak”. Gehrels and Scotti acquired images of the comet during July 21–22. For the latter date, they gave the magnitude as 18.1 and noted a tail extending 3000 in PA 110
. The comet’s elongation steadily decreased as the year progressed, and it also continued its southward movement. It attained its most southerly declination of 29
on December 19 and reached a minimum elongation of 7
on 1988 January 13. After having moved northward since last December, the comet attained a declination of 18
on 1988 June 10 and then began a southerly motion. The final observations of this comet came during 1988 September 10.43–10.45 and September 11.44–11.47, when K. J. Meech (Mauna Kea, Hawaii, USA) acquired CCD images using the 224-cm reflector. She estimated the nuclear magnitude as 21. The final position was α = 23h 53.1m, δ = 24
540 (2000) on September 11.46. The comet had reached a maximum elongation of 158
on September 10. Multiple apparition orbits have been calculated by D. W. E. Green (1987, 1989), Nakano (1998, 2005, 2012), K. Kinoshita (1998, 2001), and B. G. Marsden (1998, 2005). All of these calculations included full planetary perturbations, while those published from 1998 onward also solved for nongravitational effects. The perihelion date was determined as September 1.06 and the period was 6.90 years. Nakano (1998), Kinoshita (1998), and Marsden (1998) revealed nongravitational terms within the following ranges: A1 = +0.29 to +0.39 and A2 = +0.1460 to +0.1463. Adding positions from the 2001 apparition, Kinoshita (2001), Marsden (2005), and Nakano (2005) revealed nongravitational terms within the following ranges: A1 = +0.46 to +0.87 and A2 = +0.1095 to +0.1133. With the comet having been missed at its 2008 apparition, Nakano (2012) redetermined the orbit using the positions from 1980–2001 and gave the nongravitational terms as A1 = +0.10 and A2 = +0.0801. The orbit of Kinoshita (2001) is given below. 257

cometography: a catalog of comets T ω Ω (2000.0) i q e 1987 Sep. 1.0574 (TT) 179.5916 72.6695 15.4559 2.291864 0.367467

absolute magnitude: H10 = 13.4 (Kronk) full moon: 1987 Jan. 15, Feb. 13, Mar. 15, Apr. 14, May 13, Jun. 11, Jul. 11, Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2, Mar. 3, Apr. 2, May 1, May 31, Jun. 29, Jul. 29, Aug. 27, Sep. 25 sources: S. Nakano, Nakano Note, No. 433 (1983 Sep. 11); S. Nakano, MPC, No. 10521 (1986 Mar. 26); T. Gehrels and J. V. Scotti, IAUC, No. 4309 (1987 Feb. 2); D. W. E. Green, IAUC, No. 4311 (1987 Feb. 5); T. Gehrels and J. V. Scotti, MPC, No. 11568 (1987 Feb. 13); T. Gehrels and J. V. Scotti, MPC, No. 11686 (1987 Apr. 14); J. W. Briggs, MPC, No. 11894 (1987 Jul. 11); T. Gehrels and J. V. Scotti, MPC, Nos. 12167, 12170 (1987 Sep. 7); K. J. Meech, MPC, No. 13782 (1988 Nov. 23); D. W. E. Green, CCO, 6th ed. (1989), pp. 32, 64; S. Nakano, Nakano Note, No. 679 (1998 May 1); K. Kinoshita correspondence with G. W. Kronk (1998, 2001); B. G. Marsden, CCO, 13th ed. (1999), pp. 74–5; B. G. Marsden, CCO, 16th ed. (2005), pp. 122–3; S. Nakano, Nakano Note, No. 1199 (2005 Jul. 4). 87P/1987 B4 Recovered: 1987 January 29.33 (Δ = 2.08 AU, r = 3.02 AU, Elong. = 161
) (Bus) Last seen: 1988 July 16.26 (Δ = 1.71 AU, r = 2.61 AU, Elong. = 146
) Closest to the Earth: 1988 June 3 (1.4797 AU) 1987 Calculated path: GEM (Rec), CNC (May 11), LEO (Jul. 5), VIR (Sep. 16), LIB XXXIV=1987f (Dec. 6), SCO (1988 Jan. 24), OPH (Feb. 4), SGR (Mar. 27), OPH (Jun. 7) S. Nakano (1985, 1986) determined an orbit for this apparition using 18 positions from 1981 February 9 to June 27 and full planetary perturbations. He predicted the comet would next arrive at perihelion on 1987 December 21.34. S. W. Milbourn (1986) took the orbit calculated by B. G. Marsden for the 1981 apparition and applied full planetary perturbations to predict the next perihelion date as December 19.52. This comet was recovered by T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) during 1987 January 29.33–29.41 when they acquired five CCD images using the 91-cm reflector. They described the comet as magnitude of 19.5 with a diffuse coma 1700 across. The position on the first image was α = 7h 24.0m, δ = +18
350 (2000). Gehrels and Scotti acquired additional CCD images during February 1.28–1.32. The only additional observations made during 1987 also came from Gehrels and Scotti, as they acquired images on February 28 and March 2. No physical descriptions were provided. After having moved northward since its recovery, the comet attained a declination of +20
on March 31 and then began a southerly motion. The comet reached a minimum elongation of 0.2
on September 18. After having moved southward since last March, the comet attained a declination of 21
on 1988 March 9 and then began a northerly motion. 258

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The first observations acquired during this year came from A. C. Gilmore (Mt. John University Observatory, Lake Tekapo, New Zealand) on June 14 and 19, but no physical descriptions were provided. The comet reached a maximum elongation of 176
on June 15. After having moved northward since early March, the comet attained a declination of 19
on June 26 and then began a southerly motion. The final observations of this comet came on 1988 July 15.26 and July 16.26, when S. J. Bus (Lowell Observatory, Anderson Mesa Station, Arizona, USA) obtained CCD images using the 183-cm reflector. No physical descriptions were provided. The position on the last date was α = 17h 18.0m, δ = 19
090 (2000). Multiple apparition orbits have been calculated by D. W. E. Green (1987, 1992), B. G. Marsden (1996, 2005), Nakano (1997, 2004, 2010), and K. Kinoshita (2000, 2007). All of these calculations included full planetary perturbations, while those published from 1996 onward also solved for nongravitational effects. The result was a perihelion date of December 19.50–19.52 and a period of 6.54 years. The orbits of Marsden (1996) and Nakano (1997) revealed nongravitational terms within the following ranges: A1 = +2.05 to +2.28 and A2 = 0.4243 to 0.4379. Adding positions from the 2000 apparition, Kinoshita (2000), Nakano (2004), and Marsden (2005) revealed nongravitational terms within the following ranges: A1 = +0.38 to +0.60 and A2 = 0.3532 to 0.3556. Kinoshita (2007) used positions from 1981–2007 to determine nongravitational terms of A1 = +0.96 and A2 = 0.3581. Nakano (2010) used positions from 1987–2007 to determine nongravitational terms of A1 = +1.90 and A2 = 0.3364. The orbit of Marsden (2005) is given below. T ω Ω (2000.0) i q e 1987 Dec. 19.5049 (TT) 24.5312 182.2121 2.5701 2.192777 0.372792

absolute magnitude: H10 = 13.1 (Kronk) full moon: 1987 Jan. 15, Feb. 13, Mar. 15, Apr. 14, May 13, Jun. 11, Jul. 11, Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2, Mar. 3, Apr. 2, May 1, May 31, Jun. 29, Jul. 29 sources: S. Nakano, Nakano Note, No. 488 (1985 Dec. 22); S. Nakano, MPC, No. 10522 (1986 Mar. 26); S. W. Milbourn, BAA Handbook for 1987 (1986 Oct.), pp. 88; T. Gehrels, J. V. Scotti, and D. W. E. Green, IAUC, No. 4310 (1987 Feb. 5); T. Gehrels and J. V. Scotti, MPC, Nos. 11568–9 (1987 Feb. 13); T. Gehrels and J. V. Scotti, MPC, Nos. 11686–7 (1987 Apr. 14); A. C. Gilmore and S. J. Bus, MPC, No. 13358 (1988 Aug. 27); D. W. E. Green, CCO, 7th ed. (1992), pp. 32, 67; B. G. Marsden, CCO, 11th ed. (1996), pp. 68–9; S. W. Milbourn, CCO, 12th ed. (1997), pp. 70–1; S. Nakano, Nakano Note, No. 662 (1997 May 4); K. Kinoshita correspondence with G. W. Kronk (2000, 2007); S. Nakano, Nakano Note, No. 1051 (2004 Apr. 7); B. G. Marsden, CCO, 259

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16th ed. (2005), pp. 122–3; S. Nakano, Nakano Note, No. 1931 (2010 Apr. 29); B. A. Skiff correspondence with G. W. Kronk (2011, 2012). 10P/Tempel 2 Recovered: 1986 December 29.46 (Δ = 3.81 AU, r = 4.26 AU, Elong. = 111
) Last seen: Visible throughout orbit 1988 XIV=1987g Closest to the Earth: 1988 June 28 (0.7691 AU) Calculated path: LEO (Rec), VIR (1987 Aug. 31), LIB (1988 Jan. 11), SER (Mar. 10), LIB (Jul. 11), SCO (Aug. 12), OPH (Aug. 23), SGR (Sep. 19), MIC (Nov. 3), CAP (Nov. 17), PsA (Nov. 20), CAP (Nov. 28), AQR (Nov. 29), CET (1989 Jan. 12), PSC (Mar. 13), CET (Mar. 16), TAU (Apr. 27), ORI (Jun. 14), TAU (Jul. 14), ORI (Aug. 3), GEM (Sep. 2), ORI (Dec. 10), TAU (1990 Jan. 16), ORI (Mar. 26), GEM (May 7), CNC (Aug. 11), GEM (1991 Mar. 2), CNC (Apr. 27) The prediction for the return of this comet was not actually published until a couple of weeks after the comet’s recovery, but ten days before it was finally confirmed. D. K. Yeomans (1987) took 110 positions from the years 1961–1983, included perturbations by all nine planets, and solved for nongravitational effects. He then integrated the comet’s motion to this apparition and predicted the next perihelion date as 1988 September 16.73. This comet was recovered by T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) on three CCD images acquired during 1986 December 29.46–29.49 while using the 91-cm reflector. They judged the magnitude as 20.4 and the position on the first image as α = 11h 22.6m, δ = +12
370 (2000). The comet was not announced until a second set of images was acquired. This finally happened during 1987 January 25.38–25.42, when five images were obtained using the same instrumentation. Gehrels and Scotti then gave the magnitude as 20.0. The comet was observed from two observatories in 1987. Gehrels and Scotti acquired images on March 27 and May 23, which revealed the magnitude as 19.8. K. J. Meech (Kitt Peak National Observatory, Arizona, USA) acquired CCD images during March 31–April 3 using the 213-cm reflector. These revealed a stellar object, the magnitude of which varied from 19.48 to 19.81. Meech and her colleague, D. C. Jewitt, suggested possible rotation periods of 7.5 and 8.9 hours, but noted these did not “lead to a convincing light curve, and we do not claim to have detected the rotation period.” They added that the comet might have been “weakly active.” Meanwhile, the comet reached a maximum elongation of 170
on February 27 and a minimum elongation of 8
on September 24. After having moved northward since its recovery, the comet attained a declination of +21
on April 21 and then began a southerly motion. The comet was followed from several observatories in 1988. Meech acquired images during February 10–16, April 14–17, and May 17–19, using the 224-cm reflector at Mauna Kea (Hawaii, USA), and on March 25, using the 152-cm reflector at Cerro Tololo Inter-American Observatory (Chile). 260

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M. J. S. Belton and E. M. Alvarez acquired images on every night from March 18–22 using the 224-cm reflector at Mauna Kea. Jewitt and J. X. Luu acquired images on February 25, February 27–29, June 22–23, June 26, and September 9 using the 236-cm Ritchey-Chrétien reflector at McGraw-Hill Observatory (Arizona, USA). They also obtained images during April 9–15 and June 30–July 1, using the 127-cm reflector at McGraw-Hill Observatory, and on July 13, using a 91-cm reflector at Kitt Peak National Observatory. Jewitt and Luu made a preliminary announcement in the International Astronomical Association Circular on April 19 concerning their April observations. They noted, “The comet’s image is stellar and exhibits cyclic brightness variations of approximate period 9 hr (two maxima per period) and peak-to-peak range 0.7 mag. These observations are compatible with the direct detection of the nucleus of P/Tempel 2. An aspherical (2:1 axis ratio) nucleus is implied.” They gave the mean Mould R magnitude as 17.30.1 and added that the “inferred mean absolute red magnitude” of the nucleus was 14.30.2, which was “about 1 mag fainter than the nucleus of P/Halley.” They published a formal analysis in the 1989 June issue of the Astronomical Journal. Jewitt and Luu determined that the mean red magnitude was 18 in February and 17 in April, while the comet “was clearly active” by June. They said the February photometry best fit a rotation period of 8.94 hours, while the April photometry fit a rotation period of 8.95 hours. The mean absolute magnitude of the nucleus during both periods was 14.3. During this same period, the comet attained a declination of 5
on February 8 and then moved northward to a declination of +4
on May 26. The comet reached a maximum elongation of 156
on May 17. Two other observatories provided observations in May. A series of short exposures were obtained at La Silla Observatory (Chile) on May 16 using the 154-cm reflector. W. Wisniewski (Catalina Station, Mt. Bigelow, Arizona, USA) acquired images during May 20–22 using the 154-cm reflector. Wisniewski confirmed the rotation period suggested by Jewitt and Luu, noting the best fit to his data was 8 hours 58 minutes. He added that the amplitude was smaller, being only 0.2 magnitude, which he suggested was an indication of coma development. This coma development was actually confirmed by the La Silla images a few days earlier, with R. M. West reporting, “A fan-shaped dust tail extends over p.a. 230 to 290 deg, with denser parts at the edges and also at p.a. 260 deg. The 230- to 260-deg sector can be followed to at least 3500 from the asymmetric, diffuse coma. The B images show a faint, short extension near p.a. 290 deg.” Also in 1988, visual observers began looking for the comet as early as April 22; however, despite the experience level of some of the observers, including A. Hale (Las Cruces, New Mexico, USA) and C. S. Morris (California, USA), the comet was not spotted with confidence and was said to be fainter than magnitude 13.5. Morris finally succeeded in definitely seeing the comet on June 4, when his 26-cm reflector revealed a magnitude 261

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of 13.1 and a slightly condensed coma 1.20 across. M. Amoretti (Sanremo, Italy) reported seeing the comet with his 35-cm reflector on June 11. He gave the magnitude as 12.3 and noted the coma was very strongly condensed. D. H. Levy (Catalina Station, Mt. Bigelow, Arizona, USA) saw the comet using the 154-cm reflector on June 13. He estimated the magnitude as 13.5 and said the strongly condensed coma was 0.20 across. The majority of visual observers reported the comet was very slightly condensed during July. This led to the comet appearing over a magnitude fainter in large telescopes than in smaller ones. J. E. Bortle (Stormville, New York, USA) observed the comet with his 50-cm reflector on the 3rd and 4th, giving the magnitude as 13.0 and 13.3, respectively. He said the coma was 0.50 across. Hale was observing with his 41-cm reflector on the 3rd and gave the magnitude as 13.8. K. T. Cernis (Lithuania) observed the comet on the 6th, using his 25-cm reflector, and estimated the magnitude as 11.5. He noted that the coma was 10 across. Another observation by Cernis on the 10th indicated a magnitude of 11.6 and a coma 1.50 across. Hale next saw the comet on the 11th and 12th, noting magnitudes of 13.4 and 13.3, respectively. Morris and Cernis also saw the comet on the 12th. Morris gave the magnitude as 12.5 and said the coma was 1.90 across. Cernis was using 20  110 binoculars and estimated the magnitude as 11.0. He added that the coma was 2’ across. Bortle and Hale independently observed the comet on the 16th. Bortle reported a magnitude of 12.1 and a coma 1.60 across. Hale gave the magnitude as 12.7. During the 13th to the 18th, Cernis gave magnitudes of 10.7–11.2 and reported a coma 3–60 across. During the 15th to the 19th, Morris gave magnitudes of 10.7–11.1 and reported a coma 3.5–80 across. The comet was most observed during August, and it brightened throughout the month as it continued to approach perihelion. A. R. Pearce (Western Australia, Australia) and D. A. J. Seargent (The Entrance, New South Wales, Australia) were among the most prolific observers and were the only observers to follow the comet for the entire month. Pearce followed the comet from the 1st through the 31st, using his 20-cm reflector, and reported the magnitude increased from 11.3 to 9.4. Seargent used his 15  80 binoculars to observe the comet from the 2nd through the 30th. He said the magnitude brightened from 9.4 to 8.5. Both observers noted very little condensation early in the month and moderate condensation during the last days of the month. Although both observers reported some variations in the coma size throughout the month, these were probably more a result of seeing conditions than actual changes. Pearce’s reflector revealed coma diameters that ranged from 2.5–4.50 , while Seargent’s binoculars revealed diameters of 6–100 . Morris reported a tail on two nights while using his 26-cm reflector. He said it extended 20 in PA 350
on the 9th and 30 in PA 320
on the 12th. Pearce, Hale, and Morris were the top observers during September. Pearce mostly used his 20-cm reflector and noted the magnitude brightened 262

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from 9.5 on the 2nd to 8.8 by the 15th. The coma varied from 4–50 across, while the condensation was slight to moderate. Among Hale’s observations were three made with his 10  50 binoculars, which revealed the magnitude brightened from 9.4 on the 3rd to 8.5 by the 15th. Most of Morris’ observations were made using 20  80 binoculars. He actually noted the comet faded slightly, being at magnitude 8.2 on the 7th and 8.4 by the 17th. Morris added that the coma remained slightly condensed with a diameter of 7.5–80 . Morris reported observations of the tail on two nights. Using his 26-cm reflector, he said it extended 50 in PA 300
on the 10th and 40 in PA 300
on the 11th. Observations continued to dwindle during October as the comet faded. Hale saw the comet with his 10  50 binoculars on the 1st, 3rd, and 13th, and gave the magnitude as 8.8 each night. He switched to his 41-cm reflector on the 28th and gave the magnitude as 9.5. Morris saw the comet with his 20  80 binoculars on the 9th, giving the magnitude as 8.7. He also reported a slightly condensed coma 60 across. He also saw the comet with his 26-cm reflector on the same night, reporting the same magnitude and level of condensation, but noting a coma diameter of 40 . Morris used his reflector on the 10th and 31st, noting the magnitude faded from 8.8 to 9.2. Although the coma remained slightly condensed, its diameter was given as 3.60 and 5.20 , respectively. The comet attained its most southerly declination of 31
on October 18. The final binocular observations were made by Seargent and R. Haver (Rome, Italy) early in November. Using 15  80 binoculars, Seargent saw the comet on the 2nd and 8th, giving the magnitude as about 9.6 and 9.9, respectively. Haver also used 15  80 binoculars on the 5th and gave the magnitude as 9.3. He added that the coma was slightly condensed and 6.50 across. Only a few observations were made during the remainder of November. Hale saw the comet with his 41-cm reflector on the 12th and gave the magnitude as 10.2. On the 13th, Morris observed with his 26-cm reflector and gave the magnitude as 10.0. He noted the coma was very slightly condensed and 30 across. Another observation was made by Hale on the 27th, at which time he gave the magnitude as 10.4. Pearce saw the comet using his 20-cm reflector on the 26th, 27th, and 28th. He gave the magnitude as 10.0 on the first date and 10.1 on the last two dates. Pearce said the coma was slightly condensed and 3–40 across. Only a handful of observations were made during December, as the comet continued to fade. Hale observed the comet on three nights using his 41-cm reflector. He gave the magnitude as 10.6 on the 3rd, 11.4 on the 12th, and 11.3 on the 28th. Only the slightest trace of condensation was noted. Morris was using his 26-cm reflector and gave the magnitude as 10.7 on the 11th and 11.9 on the 30th. He also noted that the coma was very slightly condensed. Morris gave the coma diameter as 2.80 on the 11th and 1.60 on the 30th. 263

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The last visual observations were made during 1989 January, with all observers reporting a very slightly condensed coma. Hale reported a magnitude of 11.4 on the 1st. J. Kobayashi (Japan) observed the comet using a 31-cm reflector on the 2nd. He gave the magnitude as 13.1 and said the coma was 1.50 across. Hale reported magnitudes of 11.5 and 11.4 on the 5th and 9th, respectively. Hale also tried to see the comet on January 26, but no trace was seen. He suggested the magnitude was then fainter than 11.5. Meech acquired the only observations during the remainder of 1989. Using the 224-cm reflector at Mauna Kea, she acquired seven CCD images on February 8. Her next observation was made using the 358-cm Canada– France–Hawaii Telescope at Mauna Kea on December 27 and 29, when she obtained two CCD images on the first date and 11 CCD images on the second date. The comet reached a minimum elongation of 8
on May 23 and a maximum elongation of 172
on December 24. After having moved northward since last October, the comet attained a declination of +16
on August 4. It then moved southward until reaching a declination of +15
on November 8. Meech acquired the only images during 1990. Using the 402-cm reflector at the Cerro Tololo Inter-American Observatory, she acquired 10 CCD images on the night of April 29/30. Back at Mauna Kea, she used the 224-cm reflector to acquire 22 CCD images of the comet on December 15. The comet reached a minimum elongation of 1.7
on July 12. After having moved northward since last November, the comet attained a declination of +21
on May 31. It then moved southward until reaching a declination of +17
on November 5. The comet was nearing aphelion as 1991 began and reached a maximum elongation of 179
on January 24. Meech acquired 11 CCD images of the comet on February 13, using the 224-cm reflector at Mauna Kea. She described the comet as “stellar.” B. E. A. Mueller (Kitt Peak National Observatory, Arizona, USA) acquired CCD images of the comet on April 11, using the 213-cm reflector, but provided no description. The comet attained its most northerly declination of +23
on April 9. The comet was last detected during 1991 May 15.16–15.17 and May 16.16–16.18, when Mueller acquired CCD images of the comet using the 213-cm reflector. She estimated the magnitude as 21 on the 16th. The position was α = 8h 09.6m, δ = +22
290 (2000) on the final image. The comet was located at an elongation of 65
when last detected. It passed aphelion on June 13. Z. Sekanina (1987, 1988) used observations of a sunward fan-like coma during nine of the comet’s apparitions to determine the position of the rotation axis of this comet. In a paper published in 1987 September, he derived an obliquity of 54
and said the latitude of the southernmost boundary of the active source was +60
. In IAU Circular number 4553, published on 1988 February 23, Sekanina noted that Earth was then within 10 degrees of the comet’s equatorial plane and that conditions were right 264

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“for detecting large brightness variations due to nuclear rotation.” In IAU Circular number 4624, published on 1988 July 8, Sekanina said observations by Jewitt and Meech in 1987 and 1988 “suggests that the nuclear dimensions are about 18  11  7 km.” In addition, based on the albedo suggested by M. A’Hearn, H. Campins and D. Schleicher (1988), the size of the active area was between 1.2 and 2.8 square kilometers. A’Hearn, Campins and Schleicher (1988) provided details of their observations using the 224-cm reflector and the Infrared Telescope Facility on Mauna Kea (Hawaii, USA). They confirmed a rotation period of about 9 hours (noted above) and added, “The effective nuclear radius at maximum is 5.6  0.2 km, with geometric albedo 0.024  0.005, and axial ratio greater than or equal to 1.9.” The spectrum was observed by A’Hearn, P. Feldman, E. E. Roettger, and Schleicher (1988) using both the International Ultraviolet Explorer (IUE) and the 224-cm reflector on Mauna Kea. They detected water, cyanogen, and diatomic carbon. For his PhD in astronomy, T. L. Farnham (1996) examined images acquired by Meech from 1988 May 18 to 1989 February 9. He concluded “that the dust in the tail of P/Tempel 2 is composed of particles larger than 10 μm, with a dominant size of ~30 μm. The images contain no convincing evidence for the existence of small particles, which makes the particle distribution somewhat unusual.” Farnham added that the, “Sekanina model of the nucleus works well for reproducing the basic shape of the tail. The orientation of the pole creates an elongation of the model coma that duplicates the elongation observed in the comet, and the orientation of the pole provides an explanation for the rapid increase in activity during the months before perihelion.” Multiple apparition orbits have been calculated by Yeomans and P. W. Chodas (1989), S. Nakano (1996, 2001, 2002, 2007, 2012), and K. Kinoshita (2000, 2003, 2010). All of these calculations included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of about September 16.73 and a period of 5.29 years. The nongravitational terms were within the following ranges: A1 = +0.02 to +0.05 and A2 = +0.0010 to +0.0014. The orbit of Nakano (2012) is given below. T ω Ω (2000.0) i q e 1988 Sep. 16.7345 (TT) 191.0640 119.7928 12.4282 1.383423 0.544430

absolute magnitude: H0 = 5.6, n = 9.8 (Kronk) full moon: 1986 Dec. 16, 1987 Jan. 15, Feb. 13, Mar. 15, Apr. 14, May 13, Jun. 11, Jul. 11, Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2, Mar. 3, Apr. 2, May 1, May 31, Jun. 29, Jul. 29, Aug. 27, Sep. 25, Oct. 25, Nov. 23, Dec. 23, 1989 Jan. 21, Feb. 20, Mar. 22, Apr. 21, May 20, Jun. 19, Jul. 18, Aug. 17, Sep. 15, Oct. 14, Nov. 13, Dec. 12, 1990 Jan. 11, Feb. 9, 265

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Mar. 11, Apr. 10, May 9, Jun. 8, Jul. 8, Aug. 6, Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30, Apr. 28, May 28, Jun. 27 sources: D. K. Yeomans, MPC, No. 11522 (1987 Jan. 15); T. Gehrels and J. V. Scotti, IAUC, No. 4312 (1987 Feb. 5); T. Gehrels and J. V. Scotti, MPC, No. 11569 (1987 Feb. 13); T. Gehrels and J. V. Scotti, MPC, No. 11782 (1987 May 13); T. Gehrels and J. V. Scotti, ICQ, 9 (1987 Jul.), p. 119; T. Gehrels and J. V. Scotti, MPC, No. 11894 (1987 Jul. 11); Z. Sekanina, ESASP, No. 278 (1987 Sep.), pp. 323–36; Z. Sekanina, IAUC, No. 4553 (1988 Feb. 23); D. C. Jewitt and J. X. Luu, IAUC, No. 4582 (1988 Apr. 19); D. C. Jewitt and K. J. Meech, APJ, 328 (1988 May 15), 974–86; R. M. West, IAUC, No. 4599 (1988 May 16); W. Wisniewski, IAUC, No. 4603 (1988 May 25); M. A’Hearn, H. Campins, and D. Schleicher, IAUC, No. 4614 (1988 Jun. 15); A. Hale, C. S. Morris, M. Amoretti, and J. E. Bortle, ICQ, 10 (1988 Jul.), p. 86; M. A’Hearn, P. Feldman, E. E. Roettger, and D. Schleicher, IAUC, No. 4622 (1988 Jul. 5); Z. Sekanina, D. C. Jewitt, K. J. Meech, M. A’Hearn, H. Campins, and D. Schleicher, IAUC, No. 4624 (1988 Jul. 8); J. E. Bortle, A. Hale, and C. S. Morris, IAUC, No. 4628 (1988 Jul. 15); J. E. Bortle and C. S. Morris, IAUC, No. 4649 (1988 Sep. 1); C. S. Morris, IAUC, No. 4656 (1988 Sep. 26); C. S. Morris and A. Hale, ICQ, 10 (1988 Oct.), pp. 120–1; A. Hale and C. S. Morris, IAUC, No. 4670 (1988 Nov. 1); R. Haver, A. Hale, and C. S. Morris, IAUC, No. 4694 (1988 Dec. 22); A. R. Pearce, D. A. J. Seargent, A. Hale, and C. S. Morris, ICQ, 11 (1989 Jan.), pp. 20–2; A. Hale, ICQ, 11 (1989 Apr.), p. 34; D. C. Jewitt and J. X. Luu, AJ, 97 (1989 Jun.), pp. 1766–90; D. K. Yeomans and P. W. Chodas, AJ, 98 (1989 Sep.), pp. 1085, 1088–9; K. J. Meech, MPC, No. 16298 (1990 Jun. 8); D. H. Levy, ICQ, 13 (1991 Jul.), p. 130; B. E. A. Mueller, MPC, No. 18491 (1991 Aug. 25); J. Kobayashi, ICQ, 14 (1992 Jan.), p. 21; M. J. S. Belton and E. M. Alvarez, K. J. Meech correspondence with G. W. Kronk (1994); T. L. Farnham, Modeling Cometary Dust Tails with a Pseudo-Finson–Probstein Technique. Unpublished doctoral dissertation, University of Hawaii, Honolulu, USA (1996); S. Nakano, Nakano Note, No. 640 (1996 Apr. 11); R. Haver, ICQ, 19 (1997 Jul.), p. 205; K. Kinoshita correspondence with G. W. Kronk (2000, 2003, 2010); S. Nakano, Nakano Note, No. 776 (2001 Apr. 4); S. Nakano, Nakano Note, No. 841 (2002 May 5); K. T. Cernis, ICQ, 27 (2005 Jul.), p. 179; S. Nakano, Nakano Note, No. 1460 (2007 Apr. 10); T. L. Farnham correspondence with G. W. Kronk (2012). 299P/Catalina– Discovered: 1987 January 31.67 (Δ = 2.79 AU, r = 3.57 AU, Elong. = 136
) PanSTARRS Last seen: 1987 January 31.70 (Δ = 2.79 AU, r = 3.57 AU, Elong. = 136
) Closest to the Earth: 1988 June 6 (2.0761 AU) Calculated path: CRT (Disc) [Did not leave this constellation] This comet was discovered on 2014 February 27 and, within less than two weeks, prediscovery images were found extending back to 2013 January 21. On March 29, S. Nakano announced that he had successfully linked this 266

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comet to the asteroidal object 2005 EL284, which had been observed between March and July of 2005. With the comet’s orbit now traced through two apparitions, P. Sicoli (2014) began looking through digital archives to see if the comet could be found at an earlier date. He successfully located a trail on a 10-minute exposure acquired in 1987 with the 122-cm Schmidt telescope at Siding Spring Observatory (New South Wales, Australia). The photograph was a 10-minute exposure obtained during January 31.67–31.70 in the course of the Equatorial Red Survey. Sicoli gave the magnitude as 19.1 and noted a position of α = 11h 16.5m, δ = 8
560 (2000). G. V. Williams (2014) used 145 observations from the apparitions spanning 1987 to 2014 and included perturbations from all nine planets and Ceres, Pallas, and Vesta. He gave the perihelion date as 1988 February 10.00 and the period as 8.86 years. This was also confirmed by S. Nakano (2014), who took 155 observations from 1987–2014 and applied perturbations by Mercury to Neptune and by Ceres, Pallas, and Vesta. His orbit is given below. T ω Ω (2000.0) i q e 1988 Feb. 9.9968 (TT) 319.3835 274.6444 10.4907 3.022953 0.294135

absolute magnitude: H10 = 11.3 (Meyer) full moon: Jan. 15, Feb. 13 sources: D. W. E. Green, CBET, No. 3818 (2014 Mar. 9); S. Nakano and G. V. Williams, CBET, No. 3839 (2014 Mar. 29); P. Sicoli, MPEC, No. 2014H26 (2014 Apr. 24); P. Sicoli and G. V. Williams, MPC, Nos. 88085, 88332 (2014 May 14); S. Nakano, Nakano Note, No. 2699 (2014 May 28). 88P/1987 E1 Recovered: 1987 March 6.68 (Δ = 2.10 AU, r = 1.65 AU, Elong. = 50
) (Howell) Last seen: 1988 January 13.21 (Δ = 2.74 AU, r = 2.80 AU, Elong. = 83
) Closest to the Earth: 1987 September 10 (1.1832 AU) 1987 VI=1987h Calculated path: SGR (Rec), CAP (Mar. 12), AQR (Apr. 18), PSC (Jun. 5), CET (Jun. 21), PSC (1988 Jan. 12) Predictions for the return of this comet were published by S. Nakano (1985, 1986) and S. W. Milbourn (1986). These used positions from the discovery apparition, as well as perturbations by all nine planets. The perihelion date was predicted as 1987 April 14.76 by Nakano and April 14.50 by Milbourn. This comet was recovered by A. C. Gilmore and P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) on two photographs acquired using a 61-cm reflector. The first image was a 30-minute exposure obtained on 1987 March 6.68, while the second was a 36-minute exposure obtained on March 6.70. The position on the first image was α = 19h 50.8m, δ = 21
570 (2000). Confirmation photographs were acquired on March 7.68 and March 7.70. The nuclear magnitude was 267

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estimated as 18 on the 6th and 7th, while the comet was described as diffuse, with condensation. The comet was next observed during June. Astronomers at Lowell Observatory’s Anderson Mesa Station (Arizona, USA) acquired CCD images using the 183-cm reflector on June 23. No descriptive information was provided. A few days later, A. Hale (Las Cruces, New Mexico, USA) visually spotted the comet using his 41-cm reflector. He estimated the magnitude as 13.3 on the 29th and 12.9 on the 30th. Hale had been visually searching for the comet since March 28, hoping to catch a glimpse as soon as it had brightened enough. The comet’s brightness changed very little during July and the coma remained very slightly condensed. C. S. Morris (near Mt. Wilson, California, USA) observed the comet using his 26-cm reflector on the 1st. He gave the magnitude as 12.6 and said the coma was 1.80 across. On the same night, Hale gave the magnitude as 13.0. Hale gave the magnitude as 12.9 on the 6th. On the 7th, Morris gave the magnitude as 12.8 and said the coma was 2.00 across. After a period of moonlight, three observers spotted the comet on the 25th. Hale gave the magnitude as 12.7. M. L. Clark (Perth, Western Australia, Australia) observed using his 31-cm reflector and gave the magnitude as 12.9. A. R. Pearce (Perth) observed with his 32-cm reflector and gave the magnitude as 12.8. Both Clark and Pearce added that the coma was 20 across. Pearce noted that the comet was “faint and almost totally diffuse; best seen at low power.” On the 26th, Morris (Lockwood Valley, California, USA) gave the magnitude as 12.5 and the coma diameter as 3.40 . He also reported a faint, stellar condensation of about magnitude 15. The comet continued to show little change in brightness during August. Hale gave the magnitude as 12.8 on the 1st and said the coma was very slightly condensed. On the 4th, the comet was observed by R. J. Bouma (Netherlands) and E. A. Jacobson (Evansville, Minnesota, USA) using 25-cm reflectors. Bouma gave the magnitude as 12.9 and said the very slightly condensed coma was 0.80 across. Jacobson gave the magnitude as 13.1 and noted the coma was slightly condensed and 1.10 across. After having moved northward since its recovery, the comet attained a declination of 0.5
on 1987 August 7 and then began a southward motion. On the 22nd, A. Boattini (Italy) observed the comet using his 40-cm reflector. He gave the magnitude as 12.7 and reported a slightly condensed coma about 0.290 across. Jacobson saw the comet on the 23rd, giving the magnitude as 13.4. He added that the coma was slightly condensed and 0.90 across. On the 28th, Hale gave the magnitude as 12.9. Only three observers made visual observations during September. N. Watanabe (Japan) saw the comet on the 14th using a 25-cm reflector. He gave the magnitude as 12.8 and noted a slightly condensed coma 1.00 across. Morris made his final observation of the comet on the 20th, giving the magnitude as 13.2. He added that the coma was uncondensed and about 20 across. R. A. Keen (Colorado, USA) saw the comet using his 268

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32-cm reflector on the 23rd. He gave the magnitude as 13.7 and noted a very slightly condensed coma 1.0’ across. T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired CCD images of the comet on the 1st, using the 91-cm reflector. The magnitude was given as 15.4 and the nuclear magnitude was 17.6. They added that the coma was moderately condensed and the tail extended >9.60 in PA 244
. Despite the comet reaching a maximum elongation of 171
on October 5, only a few observations were made in October. Keen made his final observation on the 1st, giving the magnitude as 13.8. He added that the coma was uncondensed and 1.00 across. Bouma used a 51-cm reflector and gave the magnitude as 14.2 on the 20th and 23rd, and 14.4 on the 30th. He noticed no condensation on the first and last dates, but said the coma was slightly condensed on the 23rd. The coma diameters were 0.7–0.9’. S. Ueda (Kushiro, Hokkaido, Japan) photographed the comet on the 25th with a 16-cm reflector. He estimated the magnitude as 14. After having moved southward since early August, the comet attained a declination of 4
on October 24 and then began a northward motion. The only observation made during the remainder of the year came from Oak Ridge Observatory (Massachusetts, USA). Using the 155-cm reflector, C.-Y. Shao obtained a 41-minute exposure using a Kodak IIIa-F (red) photographic plate. No descriptive information was provided. The comet was last detected during 1988 January 9.16–9.17 and January 13.20–13.21, when J. B. Gibson (Palomar Observatory, California, USA) acquired CCD images using the 152-cm reflector. No descriptions were provided. The position on the final image was α = 1h 02.7m, δ = +2
430 (2000). Multiple apparition orbits have been calculated by B. G. Marsden (1987, 1996), Nakano (1989, 1998, 1999, 2001, 2004, 2005, 2014), Milbourn (1989), P. Rocher (2000, 2001, 2003, 2004), and K. Kinoshita (2004). All of these calculations included full planetary perturbations, while those published from 1998 onward also solved for nongravitational effects. The perihelion date was generally given as April 14.54–14.55, while the period was 5.93 years. Nakano (1989) did include a solution for nongravitational terms (A1 = +0.28 and A2 = 0.2588), but noted it produced almost identical residuals as the orbit that did not include these terms. The remaining calculations included three or more apparitions, and most produced nongravitational terms that were within the following ranges: A1 = +0.36 to +0.47 and A2 = 0.0551 to 0.0229. Kinoshita (2004) and Nakano (2005) achieved better residuals by solving for three nongravitational terms. Kinoshita determined them as A1 = +0.47, A2 = 0.0550, and A3 = +0.11, while Nakano gave them as A1 = +0.39, A2 = 0.0551, and A3 = +0.13. The orbit of Nakano (2005) is given below. T ω Ω (2000.0) i q e 1987 Apr. 14.5439 (TT) 214.8101 75.9439 5.5688 1.612098 0.508113

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absolute magnitude: H10 = 9.4 (Kronk) full moon: Feb. 13, Mar. 15, Apr. 14, May 13, Jun. 11, Jul. 11, Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2 sources: S. Nakano, Nakano Note, No. 472 (1985 Jul. 7); S. Nakano, MPC, No. 10519 (1986 Mar. 26); S. W. Milbourn, HBAA for 1987 (1986), p. 72; C.-Y. Shao, HOPL (1987); A. C. Gilmore, P. M. Kilmartin, and B. G. Marsden, IAUC, No. 4335 (1987 Mar. 9); C. S. Morris, ICQ, 9 (1987 Jul.), p. 124; A. Hale and C. S. Morris,, IAUC, No. 4415 (1987 Jul. 7); A. R. Pearce, M. L. Clark, C. S. Morris, and A. Hale, IAUC, No. 4450 (1987 Sep. 19); A. Hale, M. L. Clark, A. R. Pearce, A. Boattini, T. Gehrels, J. V. Scotti, and R. A. Keen, ICQ, 9 (1987 Oct.), pp. 146, 170; T. Gehrels and J. V. Scotti, MPC, Nos. 12255, 12257 (1987 Oct. 7); S. Ueda, MPC, No. 12495 (1987 Dec. 5); R. J. Bouma, E. A. Jacobson, and C. S. Morris, ICQ, 10 (1988 Jan.), p. 28; C.-Y. Shao, MPC, No. 12629 (1988 Jan. 4); [Anderson Mesa], MPC, No. 12746 (1988 Feb. 2); A. Hale, ICQ, 10 (1988 Apr.), p. 56; J. B. Gibson, MPC, No. 12858 (1988 Apr. 2); S. W. Milbourn, CCO, 6th ed. (1989), pp. 32, 64; S. Nakano, Nakano Note, No. 534 (1989 May 15); N. Watanabe, ICQ, 11 (1989 Oct.), p. 46; B. G. Marsden, CCO, 11th ed. (1996), pp. 68–9; S. Nakano, MPC, No. 31205 (1998 Feb. 11); S. Nakano, CCO, 13th ed. (1999), pp. 74–5; P. Rocher correspondence with G. W. Kronk (2000, 2001, 2003, 2004); S. Nakano, Nakano Note, No. 783 (2001 Apr. 26); K. Kinoshita correspondence with G. W. Kronk (2004); S. Nakano, Nakano Note, No. 1040 (2004 Mar. 21); S. Nakano, Nakano Note, No. 1324 (2005 Apr. 12); P. M. Kilmartin correspondence with G. W. Kronk (2011); S. Nakano correspondence with G. W. Kronk (2014); J. B. Gibson, K. Peffer correspondence with G. W. Kronk (2014). 68P/Klemola Recovered: 1987 February 16.56 (Δ = 2.91 AU, r = 2.35 AU, Elong. = 47
) Last seen: 1988 December 10.45 (Δ = 3.57 AU, r = 4.49 AU, Elong. = 156
) 1987 XIV=1987i Closest to the Earth: 1987 September 10 (0.8686 AU) Calculated path: SCT (Rec), SGR (Feb. 23), AQL (Mar. 15), CAP (Mar. 27), AQL (Apr. 7), AQR (Apr. 11), PEG (Jun. 7), PSC (Jun. 14), CET (Sep. 11), PSC (Oct. 4), CET (Nov. 2), PSC (1988 Feb. 2), CET (Feb. 10), TAU (Apr. 3), ORI (May 29), TAU (Jul. 13), ORI (Jul. 22), GEM (Aug. 23), MON (Sep. 30) Predictions for the return of this comet were published by S. Nakano (1980, 1985, 1986). These used positions from the 1965 and 1976 apparitions, as well as perturbations by all nine planets. The perihelion date for this return was determined as 1987 July 22.64. The comet passed 0.94 AU from Jupiter on 1978 May 7, which very slightly increased the perihelion distance and period. This comet was recovered on two CCD images acquired during 1987 February 16.56–16.57 by J. B. Gibson (Palomar Observatory, California, USA) using the 152-cm reflector and a Gunn r filter. He said the comet was essentially stellar and of magnitude 19, while the position was α = 18h 44.2m, δ = 14
12’ (2000) on the first date. Gibson confirmed the comet 270

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during March 17.53–17.54, when he acquired three CCD images using the same equipment. He then gave the magnitude as 18 and noted a tail between about PA 210–270
, which was bordered by streamers about 1500 long, with less-extended structure visible between the streamers. The next observation was a visual one by A. Hale (Las Cruces, New Mexico, USA) on May 30. He was using his 41-cm reflector and gave the magnitude as 13.9. The comet brightened slightly during June. A. R. Pearce (Broome, Western Australia, Australia) saw it with his 32-cm reflector on the 1st and gave the magnitude as 13.3. He added that the coma was slightly condensed and 0.80 across. Hale observed the comet on the 5th, giving the magnitude as 13.7. On the 21st, M. Amoretti (Sanremo, Italy) determined the comet’s magnitude as 12.7, as seen in his 35-cm reflector. Hale gave the magnitude as 13.1 on the 23rd. C. S. Morris (California, USA) observed the comet on the 25th, using his 26-cm reflector. He gave the magnitude as 13.3 and noted a slightly condensed coma about 1.00 across. On the 27th, Morris gave the magnitude as 13.1 and reported the coma was 0.90 across. D. W. E. Green (Massachusetts, USA) observed the comet on the 29th using a 41-cm reflector and gave the magnitude as 13.1. He said the coma seemed very slightly condensed and about 0.50 across. The comet brightened only slightly during July, while the coma remained slightly condensed. Morris (near Mt. Wilson, California, USA) saw the comet on four nights. He gave the magnitude as 13.1 on the 1st and reported the coma was 0.80 across. On the 7th, Morris gave the magnitude as 13.0 and noted the coma was still 0.80 across. Morris made additional observations on the 25th and 26th, reporting a magnitude of 12.8 and the coma diameter as 1.3–1.40 . Hale observed the comet on three nights. He gave the magnitude as 13.2 on the 1st, 13.1 on the 6th, and 13.0 on the 25th. Pearce gave the magnitude as 12.9 on the 2nd. He reported a coma 0.80 across. J. E. Bortle (Stormville, New York, USA) observed the comet using his 32-cm reflector. He gave the magnitude as 12.7 and the coma diameter as 1.10 . After having moved northward since its recovery, the comet attained a declination of +8
on July 29 and then began a southward motion. The comet showed further signs of brightening in August. Hale gave the magnitude as 12.8 on the 1st and reported a moderately condensed coma. R. J. Bouma (Netherlands) observed the comet on the 3rd using a 25-cm reflector. He reported a magnitude of 12.4 and a coma diameter of 1.50 . On the 23rd, Morris (Lockwood Valley, California, USA) determined the magnitude as 12.4. He added that the coma was slightly condensed and 1.40 across. Hale gave the magnitude as 12.6 on the 28th, while Morris gave it as 12.4 on the 30th. Morris said the coma was still 1.40 across. T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired CCD images of the comet on the 17th, using the 91-cm reflector. They gave the magnitude as 14.9 and the nuclear magnitude as 17.1. Scotti added that the 271

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coma was moderately condensed and exhibited a slightly curved tail extending >7.20 from PA 236
to 248
. The comet was most observed by amateur astronomers during September and showed very little condensation. Bortle and Hale detected the comet on the 2nd. Bortle was using a 50-cm reflector and gave the magnitude as 12.7. He said the coma was 1.50 across. Hale determined the magnitude as 12.6. Hale next saw the comet on the 17th, giving the magnitude as 12.7. Bouma saw the comet on the 18th. He gave the magnitude as 12.6 and reported the coma was 2.20 across. Morris observed the comet on the 20th, giving the magnitude as 12.5 and the coma diameter as 1.80 . On the 25th, Bouma judged the magnitude as 12.7 and the coma diameter as 2.00 . The magnitude was determined as 12.8 by Morris on the 27th, while the coma was 1.30 across. Bouma and Hale gave the magnitude as 12.8 and 12.9, respectively, on the 29th. Bouma added that the coma was 1.80 across. Bouma judged the magnitude as 12.7 on the 30th, adding that the coma diameter was 2.00 . The comet reached a maximum elongation of 176
on September 28. The comet faded during October. R. A. Keen (Boulder, Colorado, USA) observed it using his 32-cm reflector on the 1st. He gave the magnitude as 12.9 and reported the coma was uncondensed and 1.00 across. Another observation was made by Keen on the 12th, when he gave the magnitude as 13.3. He added that the coma appeared very slightly condensed and 0.80 across. Hale reported a magnitude of 13.6 on the 16th. Bouma saw the comet on the 17th, judging the magnitude as 13.4. He added that the coma was uncondensed and 2.00 across. With the comet getting fainter, Bouma began using a 51-cm reflector near the end of October. He gave the magnitude as 13.6 on the 23rd and 13.5 on the 30th. Bouma reported that the coma was uncondensed and 1.2–1.30 across. M. L. Clark (Armadale, Western Australia, Australia) saw the comet using his 31-cm reflector on the 24th. He said the comet was an easy target and gave the magnitude as 13.2. He added that the coma was slightly condensed and about 2.50 across. After having moved southward since the end of July, the comet attained a declination of 6
on November 11 and then began a northward motion. Clark obtained the final visual observation on the 12th, when he gave the magnitude as 13.8. He said the comet was “very, very difficult” to see by “averted vision only.” He noted very slight condensation in a coma 1.50 across. The last observation of 1987 was made by K. J. Meech (Mauna Kea, Hawaii, USA), when she acquired four CCD images using the 224-cm reflector on November 26. The comet was not observed during most of 1988, both because of its faintness and because of its proximity to the Sun. The comet reached a minimum elongation of 8
on June 3 and then attained its most northerly declination of +15
on July 3. The comet was last detected during 1988 December 10.39–10.45, when Meech acquired five CCD images; however, no descriptions were provided. 272

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The position on the last date was α = 6h 35.0m, δ = +9
300 (2000). Meech (Cerro Tololo Inter-American Observatory, Chile) acquired nine CCD images of the comet’s predicted position during 1989 January 9.19–9.20 using the 91-cm reflector, but the comet was not detected. She attempted additional observations of this comet from Cerro Tololo on 1992 March 7, when she used the 402-cm reflector and an R filter to acquire six CCD images totaling 1200 seconds; however, no trace of the comet was found. Multiple apparition orbits have been calculated by D. W. E. Green (1992), Nakano (1995, 2006), G. V. Williams (1999), and K. Kinoshita (2000, 2008). All of these calculations included full planetary perturbations, while those published from 1995 onward also solved for nongravitational effects. The result was a perihelion date of July 22.63 and a period of 10.95 years. Nakano (1995) gave nongravitational terms of A1 = 0.33 and A2 = 0.0111. The remaining calculations gave nongravitational terms within the following ranges: A1 = 0.04 to 0.03 and A2 = 0.0023 to 0.0016. The orbit of Nakano (2006) is given below. T ω Ω (2000.0) i q e 1987 Jul. 22.6332 (TT) 154.5429 176.4841 10.9498 1.772773 0.640452

absolute magnitude: H0 = 8.4, n = 6.6, from visual observations (Meyer) full moon: Feb. 13, Mar. 15, Apr. 14, May 13, Jun. 11, Jul. 11, Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2, Mar. 3, Apr. 2, May 1, May 31, Jun. 29, Jul. 29, Aug. 27, Sep. 25, Oct. 25, Nov. 23, Dec. 23 sources: S. Nakano, Nakano Note, No. 374 (1980 Apr. 4); S. Nakano, Nakano Note, No. 475 (1985 Jul. 7); S. Nakano, MPC, No. 10520 (1986 Mar. 26); J. B. Gibson, IAUC, No. 4349 (1987 Mar. 23); J. B. Gibson, MPC, No. 11687 (1987 Apr. 14); A. Hale and A. R. Pearce, IAUC, No. 4407 (1987 Jun. 13); A. Hale, A. R. Pearce, C. S. Morris, and D. W. E. Green, ICQ, 9 (1987 Jul.), p. 134; M. Amoretti and C. S. Morris, IAUC, No. 4422 (1987 Jul. 20); A. Hale, C. S. Morris, and J. E. Bortle, IAUC, No. 4433 (1987 Aug. 13); T. Gehrels and J. V. Scotti, MPC, Nos. 12168, 12170 (1987 Sep. 7); C. S. Morris, A. Hale, A. R. Pearce, T. Gehrels, J. V. Scotti, and R. A. Keen, ICQ, 9 (1987 Oct.), pp. 171–2; C. S. Morris, M. Amoretti, A. Hale, and R. A. Keen, IAUC, No. 4462 (1987 Oct. 3); J. E. Bortle, A. Hale, C. S. Morris, R. J. Bouma, and M. L. Clark, ICQ, 10 (1988 Jan.), pp. 30–1; D. W. E. Green, CCO, 7th ed. (1992), pp. 32, 67; K. J. Meech correspondence with G. W. Kronk (1994); S. Nakano, Nakano Note, No. 623 (1995 Apr. 20); G. V. Williams, CCO, 13th ed. (1999), pp. 72–3; K. Kinoshita correspondence with G. W. Kronk (2000, 2008); S. Nakano, Nakano Note, No. 1307 (2006 Apr. 7). C/1987 F1 Discovered: 1987 March 28.26 (Δ = 2.91 AU, r = 3.63 AU, Elong. = 130
) (Torres) Last seen: 1992 January 31.57 (Δ = 12.84 AU, r = 13.34 AU, Elong. = 118
) Closest to the Earth: 1987 April 24 (2.7302 AU) 273

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1987 V=1987j Calculated path: CEN (Disc), HYA (May 8), CRV (May 27), VIR (Jul. 11), COM (1988 Feb. 8), UMa (Apr. 19), COM (Sep. 15), CVn (Oct. 8), UMa (1989 Feb. 17). DRA (1990 Jan. 15), UMa (1990 Jan. 18), DRA (1990 Feb. 3), UMa (1990 Feb. 28), DRA (1990 Nov. 9), UMa (1991 Jan. 4), DRA (1991 Jan. 16), CAM (1991 Apr. 21), UMa (1991 May 14), DRA (1991 Nov. 12), C. Torres (Cerro El Roble Observatory, Chile) discovered this comet on plates exposed on 1987 March 28.26, March 29.07, and March 29.25. The magnitude was given as 15 on the 28th and 16 on the 29th, while the comet was described as diffuse, with a condensation and a short tail. On the first date, the position was α = 13h 55.8m, δ = 49
230 (2000). The comet was confirmed by M. Kempin (Perth Observatory, Bickley, Western Australia, Australia) on April 1.34. He gave the magnitude as 16 and noted a tail 20 long. The comet was followed by three observatories during April and five during May; however, only two physical descriptions were provided. Torres photographed the comet on April 1 and estimated the magnitude as 16. T. Seki (Geisei, Kochi, Japan) photographed the comet on April 23, using his 60-cm reflector, and estimated the magnitude as 16. The comet reached a maximum elongation of 149
on April 25. Although four observatories acquired images of the comet during June, only one provided physical descriptions; however, two additional observers also provided the only visual observations. T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired CCD images of the comet on the 22nd and 23rd, using the 91-cm reflector. The magnitude was given as 15.3 on both dates, while a tail was detected on the second date that extended 4.50 , curving from PA 122
toward PA 168
. Scotti noted that this last observation was also made in twilight. D. H. Levy (Catalina Station, Mt. Bigelow, Arizona, USA) saw the comet using the 154-cm reflector on June 22. He estimated the magnitude as 13.0. Levy also noted a moderately condensed coma and a tail 30 long. C. S. Morris (California, USA) saw the comet on the 27th, using his 26-cm reflector and estimated the magnitude as 12.8. He added that the coma was slightly condensed and 1.20 across. During the remainder of 1987 the comet was only detected on two other occasions. Astronomers at Perth Observatory (Bickley, Western Australia, Australia) photographed it on July 17 and K. J. Meech (Mauna Kea, Hawaii, USA) acquired four CCD images on November 25, using a 224-cm reflector. Meech provided the only description when she noted a well-bounded coma and a “narrow parallel tail.” The comet’s elongation reached a minimum of 2
on October 6. As 1988 began, the comet was located in the southeastern morning sky. Scotti managed to acquire two images on January 15, when the comet was 54
above the horizon. He gave the nuclear magnitude as 19.2 and noted a tail extending 4.60 in PA 172
. 274

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Meech was the only observer of the comet during the remainder of its apparition. During 1988, she acquired CCD images on February 13 and 16, using the 224-cm reflector at Mauna Kea, on March 18–22 and March 24, using the 152-cm reflector at Cerro Tololo Inter-American Observatory (Chile), and on May 17 and December 9–10, using the 224-cm reflector at Mauna Kea. On all occasions, she noted, “Well bounded coma, narrow parallel tail.” The comet reached a maximum elongation of 153
on March 17 and a minimum of 30
on September 6. After having moved northward since its discovery, the comet attained a declination of +34
on June 6. It then moved slowly southward until it attained a declination of +33
on September 3. During 1989, Meech detected the comet on two nights from Mauna Kea. She acquired 12 CCD images on June 2, using the 224-cm reflector, with a total exposure time of 2400 seconds. She noted a “well bounded coma, narrow parallel tail.” On December 27, Meech acquired 14 CCD images, totaling 1800 seconds, while using the 358-cm reflector. She said the comet showed less condensation and was more diffuse than on previous images. In addition, the “parallel sided tail structure [was] gone.” These images provided the last astrometric positions, with the comet at α = 12h 13.8m, δ = +60
340 (2000) on December 27.52. The comet reached a maximum elongation of 131
on February 22 and a minimum elongation of 43
on August 16. After having moved northward since last September, the comet attained a declination of +57
on April 18 and then moved southward to a declination of +52
on September 7 before resuming a northward motion. Meech observed the comet on one night during each of the next two years. A total of 25 CCD images were acquired on 1990 December 17, using the 224-cm reflector and an R filter. Meech said there was no central condensation, but the status of the tail could not be determined because there was a low signal-to-noise ratio because of the crowded field and poor seeing. Meech acquired 32 CCD images, with a total exposure time of 7040 seconds, on 1991 February 13. She noted, “very faint tail, relatively no central condensation.” Meech added that there was “substantial tail/coma toward PA 140
.” The comet’s elongation was greatest on 1990 February 5 (124
) and 1991 January 22 (121
), while it was at a minimum elongation on 1990 July 31 (49
) and 1991 July 19 (52
). The comet was continuing to spiral northward as it moved across the sky, moving northward to +69
by 1990 March 28, southward to +63
by August 31, northward to +76
by 1991 March 10, and then southward to +69
by August 20 before resuming a northward motion. The final observations of this comet were acquired on 1992 January 5.52–5.57, January 6.37–6.43, and January 31.46–31.57 by Meech, while using the 224-cm reflector and an R filter. The total exposure times on each date were 3600, 4200, and 7200 seconds. Meech noted, “no central condensation, no tail, diffuse dust cloud only.” The predicted position at 275

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the time of the last image was α = 9h 48.0m, δ = +78
530 (2000). The comet reached a maximum elongation of 121
on January 12. Meech used the Hubble Space Telescope to image the comet’s predicted position on 1997 May 10; however, a total exposure time of 13,200 seconds failed to show the comet. Meech (1993) came to the following conclusions about this comet: “Between 9 and 13 AU” this comet “exhibited a significant change in its tail morphology. The tail became much more diffuse and unstructured with poorly defined boundaries, in contrast to the earlier narrow parallel-sided structure.” She suggested this was due to the “presence of small dust grains. Because these grains, unlike the larger ones, are affected significantly by radiation pressure, they would not have remained in the vicinity of the comet since perihelion and thus they must have been produced at large [distances from the Sun].” For his PhD in astronomy, T. L. Farnham (1996) examined images acquired by Meech during 1987 and 1988. He said there were “no distinct features in the outer coma or in the tail, but there is an asymmetry in the shape of the coma,” adding “the coma is denser on the lower (western) edge.” He concluded “The emission is dominated by large, low-velocity particles that form a narrow, long-lived tail. The absence of small grains in the tail, combined with the observations of continued emission at large [distances from the Sun], implies that there are few small particles in the nucleus.” The first orbit was calculated by D. W. E. Green and was published on 1987 April 8. It was based on six positions from March 28 to April 1 and gave the perihelion date as 1987 March 29.67. Green calculated additional parabolic orbits, which were published on May 1, May 13, and July 11. These gave perihelion dates of April 10.87, April 9.58, and April 10.30, respectively. The first hyperbolic orbit was published by Green on 1988 January 4. He used 24 positions from 1987 March 28 to July 17, determining a perihelion date of April 10.26 and an eccentricity of 1.00120. Green calculated a revised hyperbolic orbit which was published on 1988 August 27. This used 39 positions from 1987 March 28 to 1988 May 17. The result was a perihelion date of April 10.27 and an eccentricity of 1.00106. B. G. Marsden (1990) took 45 positions from 1987 March 28 to 1989 June 2 and included perturbations by all nine planets. He determined the perihelion date as April 10.28 and the eccentricity as 1.00101. Upon the publication of Meech’s final astrometric positions, Green (1990) calculated an orbit that used 43 positions from the entire apparition. The perihelion date was determined as April 10.27 and the eccentricity was 1.00101. This orbit is given below. T ω Ω (2000.0) i q e 1987 Apr. 10.2749 (TT) 329.0892 194.4877 124.0800 3.624588 1.001008

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absolute magnitude: H10 = 4.5, from visual observations (Meyer) full moon: 1987 Mar. 15, Apr. 14, May 13, Jun. 11, Jul. 11, Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2, Mar. 3, Apr. 2, May 1, May 31, Jun. 29, Jul. 29, Aug. 27, Sep. 25, Oct. 25, Nov. 23, Dec. 23, 1989 Jan. 21, Feb. 20, Mar. 22, Apr. 21, May 20, Jun. 19, Jul. 18, Aug. 17, Sep. 15, Oct. 14, Nov. 13, Dec. 12, 1990 Jan. 11 sources: C. Torres, IAUC, No. 4355 (1987 Mar. 31); C. Torres, M. Kempin, and D. W. E. Green, IAUC, No. 4360 (1987 Apr. 8); T. Seki and D. W. E. Green, IAUC, No. 4381 (1987 May 1); C. Torres, [Perth], T. Seki, and D. W. E. Green, MPC, Nos. 11782, 11831 (1987 May 13); D. W. E. Green, IAUC, No. 4394 (1987 May 15); D. H. Levy, T. Gehrels, J. V. Scotti, and C. S. Morris, ICQ, 9 (1987 Jul.), p. 117; C. Torres, T. Gehrels, J. V. Scotti, and D. W. E. Green, MPC, Nos. 11894, 11896, 12008 (1987 Jul. 11); [Perth], MPC, No. 12361 (1987 Nov. 5); D. W. E. Green, MPC, No. 12704 (1988 Jan. 4); J. V. Scotti, MPC, Nos. 12858, 12865 (1988 Apr. 2); K. J. Meech and D. W. E. Green, MPC, Nos. 13360, 13459 (1988 Aug. 27); K. J. Meech and B. G. Marsden, MPC, Nos. 15604, 15672 (1990 Jan. 11); K. J. Meech and D. W. E. Green, MPC, Nos. 16296, 16377 (1990 Jun. 8); K. J. Meech, Workshop on the Activity of Distant Comets, eds. W. F. Huebner, H. U. Keller, D. C. Jewitt, J. Klinger, and R. West, Southwest Research Institute (1993), pp. 12–20; K. J. Meech correspondence with G. W. Kronk (1994); T. L. Farnham, Modeling Cometary Dust Tails with a Pseudo-Finson-Probstein Technique. Unpublished doctoral dissertation, University of Hawaii, Honolulu, USA (1996); K. J. Meech, O. R. Hainaut, and B. G. Marsden, Icarus, 170 (2004), pp. 463–91; T. L. Farnham correspondence with G. W. Kronk (2012). 6P/d’Arrest Recovered: 1987 March 31.39 (Δ = 4.04 AU, r = 4.86 AU, Elong. = 142
) Last seen: 1989 December 27.36 (Δ = 2.39 AU, r = 3.29 AU, Elong. = 152
) 1989 II=1987k Closest to the Earth: 1989 February 1 (2.2773 AU); 1989 November 21 (2.2201 AU) Calculated path: LEO (Rec), VIR (Sep. 26), BOO (1988 Feb. 1), VIR (Mar. 3), COM (Mar. 22), VIR (Jul. 18), LIB (Oct. 1), SCO (Nov. 3), OPH (Nov. 11), SER (Nov. 29), SGR (Dec. 19), CAP (1989 Jan. 17), AQR (Feb. 16), CET (Mar. 22), PSC (Mar. 27), CET (Mar. 31), TAU (Jun. 6), ORI (Jul. 17) A prediction for the return of this comet was calculated by B. G. Marsden (1987). He took 87 positions from 1970–1982, included perturbations by all nine planets, and solved for nongravitational effects. After integrating the comet’s motion to this apparition, the predicted perihelion date was 1989 February 4.20. This comet was recovered during 1987 March 31.39–31.40, when K. J. Meech and D. C. Jewitt (Kitt Peak National Observatory, Arizona, USA) acquired two CCD images using the 213-cm reflector. They gave the position on the first image as α = 10h 31.9m, δ = +18
230 (2000) and the nuclear magnitude as 23. They noted, “The object did not appear extended through 277

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a 900 diaphragm and a broadband Mould R filter.” They confirmed the recovery during April 2.40–2.41. The comet had moved northward following its recovery, but after attaining a declination of +19
on May 2 it began a southward motion. It then reached a minimum elongation of 8
on September 14. After having moved southward since early May, the comet attained a declination of +6
on December 23 and then began a northward motion. Nearly a year would pass before the comet was observed again. Then on 1988 March 13, T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired six CCD images using the 91-cm reflector. The comet’s magnitude was given as 20.4. Meech (Cerro Tololo InterAmerican Observatory, Chile) obtained CCD images on March 24 and 25 using the 152-cm reflector. The comet reached a maximum elongation of 158
on March 31. Meech (Mauna Kea, Hawaii) acquired five CCD images of the comet on April 15 and eight on April 17 using the 224-cm reflector. She estimated the nuclear magnitude as 20 on the first night. After having moved northward since last December, the comet attained a declination of +20
on May 14 and then began a southward motion. No further observations were obtained during the remainder of 1988. The comet attained its most southerly declination of 17
on 1989 January 9, before turning northward. It then reached a minimum elongation of 0.2
on February 8. After having moved northward since early January, the comet attained a declination of +7
on July 17 and then began a southward motion. Meech was the only observer during 1989 as she continued to acquire images using the University of Hawaii’s 224-cm reflector. She obtained 18 images on August 2, 10 images on August 3, and six images on October 4, but provided no descriptions. After having moved southward since mid-July, the comet attained a declination of 1
on November 29 and then began a northward motion. The comet reached a maximum elongation of 156
on December 14. The comet was last detected during December 27.28–27.36, when Meech acquired 14 CCD images using the 358-cm Canada–France–Hawaii Telescope and V, R, and I filters. No description was provided. The position at the time of the final observation was α = 5h 16.7m, δ = +0
200 (2000). Multiple apparition orbits have been published by D. K. Yeomans and P. W. Chodas (1989), S. Nakano (1996, 1999, 2001, 2008), K. Kinoshita (2000, 2003), and Marsden (2005). These included full planetary perturbations and solved for nongravitational effects. The result was generally a perihelion date of February 4.19–4.20 and a period of 6.39 years. The nongravitational terms were given as A1 = +0.25 and A2 = +0.1146 by Yeomans and Chodas, while Nakano, Kinoshita, and Marsden gave terms in the following ranges: A1 = +0.61 to +0.88 and A2 = +0.0868 to +0.1161. The orbit of Kinoshita (2000) is given below. 278

cometography: a catalog of comets T ω Ω (2000.0) i q e 1989 Feb. 4.1902 (TT) 177.0798 139.4915 19.4237 1.291918 0.624676

absolute magnitude: H10 = 13.3 (Meyer) full moon: Mar. 15, Apr. 14, May 13, Jun. 11, Jul. 11, Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2, Mar. 3, Apr. 2, May 1, May 31, Jun. 29, Jul. 29, Aug. 27, Sep. 25, Oct. 25, Nov. 23, Dec. 23, 1989 Jan. 21, Feb. 20, Mar. 22, Apr. 21, May 20, Jun. 19, Jul. 18, Aug. 17, Sep. 15, Oct. 14, Nov. 13, Dec. 12, 1990 Jan. 11 sources: B. J. Marsden, MPC, No. 11501 (1987 Jan. 15); K. J. Meech and D. C. Jewitt, IAUC, No. 4365 (1987 Apr. 13); K. J. Meech and D. C. Jewitt, MPC, No. 11782 (1987 May 13); T. Gehrels and J. V. Scotti, MPC, No. 13004 (1988 May 1); K. J. Meech, MPC, No. 13360 (1988 Aug. 27); D. K. Yeomans and P. W. Chodas, AJ, 98 (1989 Sep.), pp. 1083–93; K. J. Meech, MPC, No. 15605 (1990 Jan. 11); K. J. Meech, MPC, No. 16298 (1990 Jun. 8); K. J. Meech correspondence with G. W. Kronk (1994); S. Nakano, CCO, 11th ed. (1996), pp. 46–7; S. Nakano, Nakano Note, No. 692 (1999 Oct. 31); K. Kinoshita correspondence with G. W. Kronk (2000, 2003); S. Nakano, Nakano Note, No. 800R (2001 Dec. 22); B. G. Marsden, CCO, 16th ed. (2005), pp. 98–9; S. Nakano, Nakano Note, No. 1625 (2008 May 28). 44P/Reinmuth 2 Recovered: 1987 April 11.49 (Δ = 2.31 AU, r = 2.48 AU, Elong. = 88
) Last seen: 1987 November 24.97 (Δ = 1.81 AU, r = 1.95 AU, Elong. = 83
) 1987 XXVI=1987l Closest to the Earth: 1987 August 8 (1.0420 AU) Calculated path: SGR (Rec), CAP (Apr. 29), SGR (Aug. 21), CAP (Sep. 15), AQR (Oct. 19) S. Nakano (1985, 1986) calculated an orbit using 65 positions from the apparitions spanning 1960–1981 and applied perturbations by all nine planets. After integrating the comet’s motion to this apparition he predicted the next perihelion date as 1987 October 25.70. This comet was recovered by J. B. Gibson (Palomar Observatory, California, USA) on three CCD images acquired on 1987 April 11.49, using the 152-cm reflector and a Gunn r filter. Gibson said the comet was nearly stellar and exhibited a nuclear magnitude of 19. The position on the first image was α = 19h 43.3m, δ = 24
490 (2000). The comet was also detected on three images acquired during April 13.47–13.48. The comet was next observed on June 24, when D. D. Balam and J. B. Tatum (Climenhaga Observatory, British Columbia, Canada) obtained two photographs. No physical description was given. A. Hale (Las Cruces, New Mexico, USA) tried to visually spot the comet using his 41-cm reflector on June 29, but was not successful. He concluded it was fainter than magnitude 14.0. The first visual observation was made by D. W. E. Green (Oak Ridge Observatory, Cambridge, Massachusetts, USA) on July 6. Using a 41-cm 279

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reflector, he determined the magnitude as 14.3. D. H. Levy (Tucson, Arizona, USA) located the comet using his 41-cm reflector on July 8 and 9, giving the magnitude as 13.7 and 13.8, respectively. He noted a moderately condensed coma 10 across. T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired three CCD images of the comet on both July 21 and July 22 using the 91-cm reflector. They estimated the magnitude as 15 on the second date. Hale located the comet on July 25, using his 41-cm reflector. He gave the magnitude as 13.5. The comet reached a maximum elongation of 178
on July 27. Visual observations continued in August. On the 16th, Hale noted a magnitude of 13.6, while C. S. Morris (Lockwood Valley, California, USA) judged the magnitude as 13.5 as seen with his 26-cm reflector. Morris added that the moderately condensed coma was 1.00 across. Another observation by Morris on the 23rd revealed a magnitude of 13.3, while the coma appearance was unchanged. Hale saw the comet on the 28th and gave the magnitude as 13.5. Gehrels and Scotti acquired a couple of CCD images on August 31, using the 91-cm reflector. They reported the magnitude as 15.7 and the nuclear magnitude as 17.2. Only two observations were reported for September. Morris gave the magnitude as 13.6 on the 20th and noted a slightly condensed coma 1.00 across. C.-Y. Shao (Oak Ridge Observatory, Massachusetts, USA) acquired a 29-minute exposure using the 155-cm reflector, but no physical description was provided. Scotti acquired three CCD images of the comet on October 15. He gave the magnitude as 15.6 and noted a tail extending 5600 in PA 72
. Hale was unsuccessful in his search for the comet on October 16 and 21. He concluded the comet must have been fainter than magnitude 13.0 on the first date and fainter than 13.5 on the second. At Oak Ridge Observatory, Shao obtained a 25-minute exposure on the 19th, while R. E. McCrosky acquired a 35-minute exposure on the 22nd. Both astronomers were using the 155-cm reflector. On November 16, McCrosky acquired a 41-minute exposure, but provided no physical description. On November 22, T. Kojima (Chiyoda, Gunma, Japan) gave the magnitude as 15. The comet was last detected on November 24.97, when McCrosky and Shao (Oak Ridge Observatory) acquired a 30-minute exposure using the 155-cm reflector. The position was α = 21h 40.5m, δ = 7
080 (2000). Multiple apparition orbits have been calculated by K. Muraoka (1992), S. Nakano (1997, 2005), B. G. Marsden (1999, 2005), and K. Kinoshita (2004). These calculations included full planetary perturbations and solved for nongravitational terms. The perihelion date was established as October 25.69, while the period was 6.72 years. The nongravitational terms were within the following ranges: A1 = 0.11 to +0.10 and A2 = 0.0194 to 0.0022. The orbit of Nakano (2005) is given below.

280

cometography: a catalog of comets T ω Ω (2000.0) i q e 1987 Oct. 25.6876 (TT) 45.4166 296.7531 6.9796 1.936020 0.456488

absolute magnitude: H0 = 9.9, n = 4.5 (Meyer) full moon: Mar. 15, Apr. 14, May 13, Jun. 11, Jul. 11, Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5 sources: S. Nakano, Nakano Note, No. 484 (1985 Dec. 16); S. Nakano, MPC, No. 10522 (1986 Mar. 26); R. E. McCrosky and C.-Y. Shao, HOPL (1987); J. B. Gibson, IAUC, No. 4369 (1987 Apr. 21); J. B. Gibson, MPC, Nos. 11778, 11782–3 (1987 May 13); D. H. Levy, ICQ, 9 (1987 Jul.), p. 122; D. W. E. Green and D. H. Levy, IAUC, No. 4417 (1987 Jul. 9); D. D. Balam and J. B. Tatum, MPC, No. 11894 (1987 Jul. 11); D. D. Balam and J. B. Tatum, MPC, No. 12033 (1987 Aug. 9); T. Gehrels and J. V. Scotti, MPC, Nos. 12166, 12168 (1987 Sep. 7); T. Gehrels, J. V. Scotti, A. Hale, C. S. Morris, ICQ, 9 (1987 Oct.), p. 170; T. Gehrels and J. Scotti, MPC, Nos. 12254, 12256 (1987 Oct. 7); J. Scotti and R. E. McCrosky, MPC, Nos. 12495, 12496, 12500 (1987 Dec. 5); C. S. Morris, T. Gehrels, J. V. Scotti, and A. Hale, ICQ, 10 (1988 Jan.), p. 27; R. E. McCrosky and C.-Y. Shao, MPC, Nos. 12627, 12629 (1988 Jan. 4); T. Kojima, MPC, Nos. 12746, 12747 (1988 Feb. 2); A. Hale, ICQ, 10 (1988 Apr.), p. 55; K. Muraoka, CCO, 7th ed. (1992), pp. 32, 67, 74; S. Nakano, Nakano Note, No. 668 (1997 Jul. 10); B. G. Marsden, CCO, 13th ed. (1999), pp. 66–7; K. Kinoshita correspondence with G. W. Kronk (2004); B. G. Marsden, CCO, 16th ed. (2005), pp. 112–13; S. Nakano, Nakano Note, No. 1191 (2005 Jun. 16); S. Nakano correspondence with G. W. Kronk (2011). 16P/Brooks 2 Recovered: 1987 April 11.50 (Δ = 2.78 AU, r = 2.43 AU, Elong. = 59
) Last seen: 1988 January 16.00 (Δ = 1.72 AU, r = 2.01 AU, Elong. = 92
) 1987 Closest to the Earth: 1987 October 2 (0.8486 AU) XXIV=1987m Calculated path: CAP (Rec), AQR (Apr. 24), PSC (May 29), CET (Sep. 18), PSC (Dec. 31) Predictions for the return of this comet were published by Z. Sekanina and D. K. Yeomans (1985) and S. Nakano (1985, 1986). These orbits used positions from the 1960, 1974, and 1980 apparitions, included full planetary perturbations, and solved for nongravitational effects. After integrating the comet’s motion forward to this apparition, the perihelion date was predicted as 1987 October 16.53 by Sekanina and Yeomans and October 16.54 by Nakano. This comet was recovered by J. B. Gibson (Palomar Observatory, California, USA), using the 152-cm reflector, a CCD camera, and a Gunn r filter on 1987 April 11.50. The position was α = 21h 31.9m, δ = 10
240 (2000). Gibson estimated the nuclear magnitude as 20 and noted a possible narrow tail extending 0.20 in about PA 270
. An additional image was obtained on

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April 11.51, while two others were obtained on April 13.50 and April 13.51. The nuclear magnitude was given as 20.5–21 on April 13.50. The next observations were made visually during the first days of July. J. V. Scotti was visiting D. H. Levy at Levy’s old Jarnac Observatory (Corona de Tucson, Arizona, USA). On the 3rd, Scotti made a possible observation of this comet using Levy’s 41-cm reflector and estimated the magnitude as 14–15. Levy was observing other objects on that night, but used the 41-cm reflector on the 4th to confirmed Scotti’s observation. He gave the magnitude as 14.1 and noted an uncondensed coma 30 across. Scotti acquired CCD images of this comet on July 21 and 22, using the 91-cm reflector. He noted a strongly condensed coma and a magnitude of 16.8. There was also a tail extending 11100 in PA 246
. The comet had steadily moved northward since its recovery and attained a declination of +5
on August 15 before turning southward. It was observed by R. J. Bouma (Netherlands) on August 3 and 7, using a 25-cm reflector. He estimated the magnitude as 13.3 on the first date and gave it as 13.4 on the second date. On both occasions, Bouma noted a slightly condensed coma about 0.50 across. Scotti visually observed the comet on the 17th, using Levy’s 41-cm reflector. He estimated the magnitude as 12.8 and noted a slightly condensed coma. A. Hale (Las Cruces, New Mexico, USA) saw the comet on the 30th and 31st, using his 41-cm reflector. He gave the magnitude as 14.2. Scotti acquired two CCD images of the comet on August 31. He gave the magnitude as 16.1 and the nuclear magnitude as 17.8. Scotti added that the tail extended 5.20 in PA 248
. Three observatories acquired images during the first three days of September, but no physical descriptions were provided. The first observations following the full moon were provided by E. A. Jacobson (Minnesota, USA) on September 14 and 15. He was using his 25-cm reflector and estimated the magnitude as 13.4 on each night. On the second night, he noted the coma was uncondensed and about 0.70 across. Hale saw the comet on the 17th and gave the magnitude as 13.6. Bouma saw the comet on the 18th. He gave the magnitude as 12.7 and noted a very slightly condensed coma 1.50 across. C. S. Morris (Lockwood Valley, California, USA) and Hale independently observed the comet on the 20th, judging the magnitude as 13.4 and 13.5, respectively. Morris said the coma was slightly condensed and 1.10 across, while Hale noted the coma was moderately condensed. An observation by Bouma on the 25th revealed a magnitude of 12.7 and a very slightly condensed coma. Morris saw the comet on the 27th. He determined the magnitude as 12.8 and said the coma was slightly condensed and 1.40 across. On the 29th, Bouma and Hale independently observed the comet, judging the magnitude as 12.7 and 13.3, respectively. Bouma said the coma was very slightly condensed and 1.40 across. Bouma saw the comet on September 30. He gave the magnitude as 12.8 and said the coma was uncondensed and about 1.50 across.

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The comet reached a maximum elongation of 178
on October 1. R. A. Keen (Boulder, Colorado, USA) and N. Watanabe (Nagaoka, Niigata, Japan) saw it on that same night and noted only slight condensation within the coma. Keen was using his 32-cm reflector, noting a magnitude of 12.5 and a coma diameter of 0.8’. Watanabe saw the comet using his 25-cm reflector and gave the magnitude as 13.5. He said the coma was 2.10 across. Jacobson saw the comet on the 3rd. He determined the magnitude as 12.8 and said the coma was 10 across. The comet was well observed following the October full moon, with most observers continuing to note only a slightly condensed coma. Keen and D. A. J. Seargent (Australia) saw it on the 12th. Keen gave the magnitude as 13.1 and the coma diameter as 1.0’. Seargent was observing with his 25-cm reflector and judged the magnitude as 13.5. He said the coma was less than 10 across. J. E. Bortle (Stormville, New York, USA) used his 50-cm reflector on the 15th to observe the comet. He gave the magnitude as 12.8 and noted a moderately condensed coma 1.00 across. Hale saw the comet on the 16th and determined the magnitude as 12.6. Keen and Bouma saw the comet on the 17th, giving the magnitude as 12.8 and 12.6, respectively. The coma diameter was given as 1.20 by Keen and about 20 by Bouma. Morris judged the magnitude as 12.4 on the 18th, noting a coma 1.10 across. On the 20th, Bouma gave the magnitude as 12.5. He reported a coma 1.60 across. Keen (Mt. Thorodin, Colorado, USA) and Bouma saw the comet on the 23rd. Keen estimated the magnitude as 13.0 and said the coma was uncondensed and 1.00 across. Bouma gave the magnitude as 12.5 and said the coma was 1.50 across. A. R. Pearce (Woodlands, Western Australia, Australia) saw the comet on the 24th using his 20-cm reflector. He gave the magnitude as 12.8 and said the coma was 10 in diameter. An observation by Hale on the 26th revealed an estimated magnitude of 12.7. Bouma saw the comet on the 29th and gave the magnitude as 12.7. He added that the coma was 1.50 across. After having moved southward since mid-August, the comet attained a declination of 2
on November 9 and then began a northward motion. Jacobson saw the comet on the same night using his 25-cm reflector and judged the magnitude as 12.6. He said the coma was moderately condensed and 20 across. Hale observed the comet on the 11th and gave the magnitude as 12.0. Jacobson and M. L. Clark (Australia) saw the comet on the 12th. Jacobson gave the magnitude as 12.6. He said the coma was slightly condensed and 1.40 across. Clark was using his 31-cm reflector and determined the magnitude as 13.3. He said the coma was slightly condensed and 1.50 across. On the 18th, Jacobson gave the magnitude as 12.9, noting a slightly condensed coma 10 across. Hale was not able to spot the comet in his 41-cm reflector on the 21st and suggested it was fainter than magnitude 13.5; however, A. Boattini (Italy) did see the comet in his 33-cm reflector on the same night and gave the magnitude as 13.0. Hale again failed to detect

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the comet with his 41-cm reflector on the 22nd and again suggested it was fainter than magnitude 13.5. Morris made the final visual observation on November 26. Using his 26-cm reflector, he determined the magnitude as 12.7 and noted a moderately condensed coma 1.40 across. The final two observations of this comet were acquired on 1987 December 19.05 and 1988 January 16.00 by R. E. McCrosky (Oak Ridge Observatory, Massachusetts, USA) using the 155-cm reflector. The photographs were exposed for 20 minutes on the first date and 36 minutes on the second. No descriptive information was provided. The position on the last date was α = 1h 48.2m, δ = +5
120 (2000). Multiple apparition orbits have been published by Yeomans and P. W. Chodas (1989), Nakano (1995, 1998, 2001, 2005), and K. Kinoshita (1998, 2001, 2003, 2009). These calculations included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of October 16.55–16.56 and a period of 6.89 years. The nongravitational terms were within the following ranges: A1 = +0.18 to +0.62 and A2 = 0.1567 to 0.1323. The orbit of Nakano (1998) is given below. T ω Ω (2000.0) i q e 1987 Oct. 16.5544 (TT) 198.1384 176.9498 5.5426 1.844798 0.490648

absolute magnitude: H10 = 10.5 (Kronk) full moon: Mar. 15, Apr. 14, May 13, Jun. 11, Jul. 11, Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2 sources: Z. Sekanina and D. K. Yeomans, AJ, 90 (1985 Nov.), p. 2336; S. Nakano, Nakano Note, No. 483 (1985 Dec. 16); S. Nakano, MPC, No. 10521 (1986 Mar. 26); S. Nakano, BAA Handbook for 1987 (1986 Oct.), p. 82; R. E. McCrosky, HOPL (1987–8); J. B. Gibson, IAUC, No. 4372 (1987 Apr. 24); J. V. Scotti and D. H. Levy, ICQ, 9 (1987 Jul.), p. 125; J. V. Scotti and D. H. Levy, IAUC, No. 4417 (1987 Jul. 9); J. V. Scotti, MPC, Nos. 12168, 12170 (1987 Sep. 7); A. Hale, IAUC, No. 4451 (1987 Sep. 22); J. V. Scotti, A. Hale, and R. A. Keen, ICQ, 9 (1987 Oct.), p. 170; J. V. Scotti, MPC, Nos. 12256–7 (1987 Oct. 7); R. A. Keen, C. S. Morris, and A. Hale, IAUC, No. 4472 (1987 Oct. 19); R. A. Keen and A. Hale, IAUC, No. 4488 (1987 Nov. 16); R. J. Bouma, C. S. Morris, A. Hale, D. A. J. Seargent, J. E. Bortle, A. R. Pearce, M. L. Clark, and A. Boattini, ICQ, 10 (1988 Jan.), pp. 28–9; R. E. McCrosky, MPC, No. 12747 (1988 Feb. 2); R. A. Keen, ICQ, 10 (1988 Apr.), p. 56; R. E. McCrosky, MPC, No. 12858 (1988 Apr. 2); D. K. Yeomans and P. W. Chodas, AJ, 98 (1989 Sep.), pp. 1083–93; E. A. Jacobson and N. Watanabe, ICQ, 11 (1989 Oct.), p. 47; S. Nakano, CCO, 10th ed. (1995), pp. 50–1; K. Kinoshita correspondence with G. W. Kronk (1998, 2001, 2003, 2009); S. Nakano, Nakano Note, No. 681 (1998 May 1); S. , Nakano, CCO, 14th ed. (2001), pp. 70–1; S. Nakano, Nakano Note, No. 1194 (2005 Jul. 4); J. V. Scotti correspondence with G. W. Kronk (2011).

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51P/Harrington Recovered: 1987 May 1.45 (Δ = 1.84 AU, r = 2.35 AU, Elong. = 108
) Last seen: 1987 November 24.60 (Δ = 1.33 AU, r = 1.61 AU, Elong. = 87
) 1987 Closest to the Earth: 1987 August 13 (0.8243 AU) XXVIII=1987n Calculated path: SGR (Rec), MIC (Oct. 10), CAP (Oct. 17), PsA (Nov. 4), CAP (Nov. 5), AQR (Nov. 17) Numerous predictions were made for this apparition. The first was by G. Sitarski (1973), who used 30 positions from the 1953 and 1960 apparitions, as well as perturbations by all nine planets, and integrated the motion of the comet up to 1988. For this apparition, he predicted the comet would arrive at perihelion on 1987 October 30.90. Sitarski added that the conditions for recovery would be good at this apparition, as the comet approached to within 0.8 AU from Earth. The comet was recovered during 1980 and Sitarski (1983) attempted to link all three apparitions to revise his prediction for the 1987 return. He noted that an apparent secular deceleration in the comet’s nongravitational motion existed and found an inconsistency in the positions from the 1980 apparition. At his request, B. G. Marsden checked into the problem and commented, “I was a little uncertain about the 1980 observations, which are not completely self-consistent with any reasonable orbit. . ..” Sitarski ultimately computed two orbits for the upcoming apparition of 1987. The orbit ignoring the 1980 positions, but using “modern values of planetary masses,” indicated a perihelion date of October 30.89. The orbit using positions from all three apparitions and a nongravitational deceleration indicated a perihelion date of October 31.98. S. Nakano (1985, 1986) and G. Forti (1986) also linked the 1953, 1960, and 1980 apparitions, including full planetary perturbations, and solving for nongravitational effects. Both noted a problem with the final position of 1980. Nakano ignored the final position and concluded that the comet would next arrive at perihelion on October 31.86. Forti decided to provide two pairs of predictions: one pair including the final position of 1980 and the other pair ignoring it. The first orbit of each pair solved for nongravitational effects, while the second orbit of each pair assumed fixed nongravitational parameters, which changed around the time of the comet’s close approach to Jupiter during 1956. Three of the orbits generated predicted perihelion dates within the range of October 31.40–31.43. The fourth orbit came from the group using all four positions from 1980 and solving for nongravitational effects. The resulting perihelion date was October 31.63. This comet was recovered during May 1.45–1.47, when T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired two CCD images using the 91-cm reflector. They estimated the magnitude as 20.0. The position on the first date was α = 19h 35.8m, δ = 15
520 (2000). Gehrels and Scotti confirmed the recovery during May 3.44–3.48, when they acquired four additional images using the same equipment.

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The magnitude was again estimated as 20.0, while the coma was 1500 across. Three additional images were acquired by Gehrels and Scotti during May 23.41–23.46. The magnitude was given as 18.9 and they noted a tail extending 1100 in PA 256
. The comet had moved slightly northward following its recovery, but after attaining a declination of 15.4
on May 25 it began a southward motion. The comet was not observed again until July, when J. Johnston (Perth Observatory, Bickley, Western Australia, Australia) acquired a 120-minute exposure using the 33-cm astrograph. The same telescope was used by M. Kempin (Perth Observatory) to obtain a 129-minute exposure on July 24. Neither Johnston nor Kempin provided a physical description. Gehrels and Scotti used the 91-cm reflector to acquire three CCD images of the comet on July 21 and another three on July 22. For the last date, the magnitude was given as 15.6 and the coma was described as moderately condensed. In addition, a tail extended 85” in PA 265
. A. Hale (Las Cruces, New Mexico, USA) tried to observe the comet using his 41-cm reflector on July 25, but failed. He concluded the comet was fainter than magnitude 13.5. The comet reached a maximum elongation of 179
on July 19. Gehrels and Scotti acquired three images on August 17 and four images on August 18. For the last date, they gave the magnitude as 15.5 and the nuclear magnitude as 18.1. The coma was fairly well condensed. Hale again tried to visually locate the comet on the 18th and 28th, but was not successful. He concluded the comet was fainter than magnitude 13.5. S. Ueda (Kushiro, Hokkaido, Japan) made the only observations in September. He photographed the comet using his 16-cm reflector on the 20th and 27th. He estimated the magnitude as 15 on the first date. The comet had been moving southward since late May, but after attaining a declination of 28
on September 28 it began a northward motion. Hale was again unsuccessful in finding the comet, concluding it was fainter than magnitude 13.0 on the 13th and fainter than 13.5 on the 19th. The very first visual observation ever acquired of this comet was made by Hale on October 16, when he gave the magnitude as 13.2. C. S. Morris (Whitaker Peak, California, USA) followed with a visual observation on the 18th. He was using a 26-cm reflector and gave the magnitude as 13.3. Morris added that the coma was uncondensed and 1.40 across. Hale saw the comet again on the 20th and gave the magnitude as 13.3. D. H. Levy (Catalina Station, Mt. Bigelow, Arizona, USA) saw the comet using the 154-cm reflector on the 26th. He estimated the magnitude as 13.0 and noted the coma was moderately condensed. E. A. Jacobson (Minnesota, USA) saw the comet on October 27 and 28, using his 25-cm reflector. For the first date, he gave the magnitude as 13.0 and noted a moderately condensed coma 10 across. On the second date, Jacobson gave the magnitude as 13.1 and said the moderately condensed coma was 1.60 across. November was the final month the comet was observed. Jacobson saw it on the 10th, giving the magnitude as 13.1 and noting a moderately 286

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condensed coma 1.20 across. Hale gave the visual magnitude as 13.3 on the 11th. A. C. Gilmore (Mt. John University Observatory, Lake Tekapo, New Zealand) obtained two photographs of the comet on the 19th, but provided no physical description. Hale attempted another visual observation on the 22nd, but was unsuccessful. He concluded the comet was fainter than magnitude 13.0. T. Kojima (Chiyoda, Gunma, Japan) used a 25-cm reflector to photograph the comet on the 22nd. He estimated the magnitude as 14.5. The final observations were obtained on November 24. Jacobson made the last visual observation on November 24.04, using his 25-cm reflector. He estimated the magnitude as 13.5. Johnston obtained a 90-minute exposure of the comet on November 24.60, using the 33-cm astrograph. No physical description was acquired, but the position was α = 22h 18.0m, δ = 20
580 (2000). Hale tried to observe the comet using his 41-cm reflector on December 10, but was unsuccessful. He concluded it must have been fainter than magnitude 13.5. Multiple apparition orbits have been calculated by S. Nakano (1995, 1998, 2001) and P. Rocher (2002). All of these calculations included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of October 31.79 and a period of 6.84 years. The nongravitational terms showed fairly large variations depending on which apparitions were used. Nakano (1995, 1998) used positions from the 1980, 1987, and 1994 apparitions and determined nongravitational terms within the following ranges: A1 = +0.72 to +0.86 and A2 = +0.0602 to +0.0611. Nakano (2001) and Rocher (2002) used positions from the 1987, 1994, and 2001 apparitions and determined nongravitational terms within the following ranges: A1 = +0.65 to +1.34 and A2 = 0.0873 to 0.0871. The orbit of Nakano (1998) is given below. T ω Ω (2000.0) i q e 1987 Oct. 31.7870 (TT) 233.0520 119.6161 8.6537 1.595911 0.557135

absolute magnitude: H0 = 5.7, n = 14.2, H10 = 11, from visual observations only (Meyer) full moon: 1987 Apr. 14, May 13, Jun. 11, Jul. 11, Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5 sources: G. Sitarski, AcA, 23 (1973), pp. 169–73; G. Sitarski and B. G. Marsden, AcA, 33 (1983), pp. 461–5; S. Nakano, Nakano Note, No. 489 (1985 Dec. 22); G. Forti, AAP, 155 (1986), pp. 169–71; S. Nakano, MPC, No. 10522 (1986 Mar. 26); S. Nakano, BAA Handbook for 1987 (1986 Oct.), p. 86; T. Gehrels and J. V. Scotti, IAUC, No. 4383 (1987 May 5); T. Gehrels and J. V. Scotti, MPC, No. 11783 (1987 May 13); T. Gehrels and J. V. Scotti, ICQ, 9 (1987 Jul.), p. 123; T. Gehrels and J. V. Scotti, MPC, Nos. 11895–6 (1987 Jul. 11); T. Gehrels and J. V. Scotti, MPC, Nos. 12168–9 (1987 Sep. 7); T. Gehrels, J. V. Scotti, and A. Hale, ICQ, 9 (1987 Oct.), p. 169; [Perth] and 287

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S. Ueda, MPC, No. 12362 (1987 Nov. 5); A. Hale, IAUC, No. 4487 (1987 Nov. 13); A. Hale, C. S. Morris, D. H. Levy, ICQ, 10 (1988 Jan.), p. 28; T. Kojima, MPC, No. 12747 (1988 Feb. 2); A. C. Gilmore, MPC, No. 12858 (1988 Apr. 2); [Perth], MPC, No. 13004 (1988 May 1); G. Forti, AAP, 215 (1989), pp. 382–3, 385; E. A. Jacobson, ICQ, 12 (1990 Jan.), p. 13; S. Nakano, CCO, 10th ed. (1995), pp. 60–1; S. Nakano, Nakano Note, No. 678 (1998 May 1); S. Nakano, MPC, No. 43161 (2001 Aug. 4); P. Rocher correspondence with G. W. Kronk (2002); J. Johnston and M. Kempin, G. Lowe correspondence with G. W. Kronk (2011); S. Nakano correspondence with G. W. Kronk (2011). C/1987 H1 Discovered: 1987 April 25.45 (Δ = 4.82 AU, r = 5.58 AU, Elong. = 136
) (Shoemaker) Last seen: 1995 January 2.5 (Δ = 18.05 AU, r = 18.78 AU, Elong. = 138
) Closest to the Earth: 1986 June 22 (4.5506 AU) 1986 XIV=1987o Calculated path: HER (Disc), SER (Jun. 1), CrB (1988 Feb. 29), BOO (Apr. 8), CVn (Jun. 29), BOO (Oct. 11), CVn (1989 Mar. 13), UMa (Apr. 10), CVn (Apr. 17), UMa (1990 Mar. 7), CVn (Nov. 17), UMa (Dec. 24) In the course of the Palomar Asteroid and Comet Survey, C. S. Shoemaker and E. M. Shoemaker (Palomar Observatory, California, USA) discovered this comet on film exposed during 1987 April 25.45–25.48 with the 46-cm Schmidt telescope. The position was α = 16h 50.7m, δ = +6
250 (2000). They estimated the magnitude as 14, and noted a tail extending 0.50 toward the southeast. B. A. Skiff (Lowell Observatory, Anderson Mesa Station, Arizona, USA) confirmed the discovery on May 4.35. He determined the magnitude as 16.8. The comet was well observed during the remainder of May. Skiff gave the magnitude as 16.5 and 16.8 on the 5th and 6th, respectively. T. Seki (Geisei, Kochi, Japan) photographed the comet on the 6th using his 60-cm reflector and noted it appeared stellar. T. Kojima (Chiyoda, Gunma, Japan) photographed the comet on the 9th using a 25-cm reflector and estimated the magnitude as 15.5. On the 16th and 18th, S. Ueda (Kushiro, Hokkaido, Japan) photographed the comet using his 16-cm reflector and estimated the magnitude as 15. The comet reached a maximum elongation of 148
on May 21. T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired CCD images of the comet on May 23 and 24 using the 91-cm reflector. The magnitude was estimated as 16 on both dates, while a tail was detected extending 50 in PA 145
on the 24th. Although several observatories followed the comet during June, there were only a handful of physical descriptions. Seki photographed the comet on the 3rd and estimated the magnitude as 17. J. W. Briggs (Chamberlin Observatory field station, Bailey, Colorado, USA) photographed the comet on the 20th using the 41-cm reflector and noted a tail 40 long. On the 22nd, Gehrels and Scotti acquired images of the comet which revealed a magnitude of 16.1 and a straight, narrow tail extending more than 5.40 in PA 140
. 288

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J. B. Gibson (Palomar Observatory, California, USA) acquired a CCD image of the comet on June 28 using the 152-cm reflector. He gave the magnitude as 17.0. Although several observatories followed the comet during July, August, and September, no physical descriptions were provided. After having moved northward since its discovery, the comet attained a declination of +15
on July 24. It then moved southward until attaining a declination of +13
on October 19. It then resumed a northerly motion. The comet reached a minimum elongation of 31
on November 7. Four observatories continued to follow the comet in 1988; however, Scotti provided the only physical descriptions. On January 15, he gave the magnitude as 16.8 and the nuclear magnitude as 18.8, noting a tail extending 1.80 toward PA 149
. On March 14, he gave the magnitude as 16.6 and the nuclear magnitude as 18.8, noting a tail extending 2.10 that curved from PA 169
to 147
. The comet reached a maximum elongation of 131
on April 19. Beginning on 1988 May 17, K. J. Meech (Mauna Kea, Hawaii, USA) provided the only observations of this comet for the remainder of its apparition. From 1988 into 1992, she used the 224-cm reflector as the comet slowly moved northward. Her final observation came on 1992 January 4.52. The magnitude was then given as 21.8, while the position was α = 11h 14.4m, δ = +52
450 (2000). This was the final astrometric position for this comet. The comet attained its most northerly declination of +56
on 1992 March 16. No further observations were made for nearly three years, as the comet generally moved very slowly toward the south, reaching maximum elongations at the end of January or early February and minimum elongations at the end of July or early August. The final observation was made on 1995 January 2.5, when Meech obtained a total exposure time of 17,300 seconds while using the 996-cm Keck I reflector, the Low Resolution Imaging Spectrometer, and an R filter. She noted a tail was still present, extending toward PA 80
. Meech used the Hubble Space Telescope to image the comet’s predicted position on 1995 December 6; however, a total exposure time of 13,000 seconds failed to show the comet. The first parabolic orbit was calculated by D. W. E. Green and was published on 1987 May 5. Green used six positions from April 25 and May 5 and determined a perihelion date of 1986 October 13.06. He claimed the perihelion date and argument of perihelion were “very uncertain.” Green published a revised parabolic orbit on May 13, when he used eight positions from April 25 to May 8 and determined the perihelion date as 1986 November 20.58. He published a further revised parabolic orbit on July 11. This used 36 positions from the period April 25 to June 26 and determined the perihelion date as November 17.16. The first hyperbolic orbit was calculated by Green and was published on 1988 January 4. He used 57 positions from April 25 to August 26 and 289

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included perturbations by all nine planets. The result was a perihelion date of November 17.09 and an eccentricity of 1.00226. Green published revisions on 1988 August 27, 1988 November 23, and 1990 June 8. The latter orbit used 82 positions from the period 1987 April 25 to 1989 December 28 and included perturbations by all nine planets. The result was a perihelion date of November 17.11 and an eccentricity of 1.00284. M. Królikowska (2014) took 127 positions from 1987 April 25 to 1992 January 4 and included full planetary perturbations. She determined the perihelion date as November 17.10 and the eccentricity as 1.00284. This orbit is given below. There were several calculations of the original and future orbits during the years this comet was under observation. The earliest was published by S. Yabushita and I. Hasegawa (1989). This indicated that both the original and future orbits were elliptical with periods of about 2.0 million and 10.4 million years, respectively. The original orbit was later corrected to 4.0 million years by Yabushita and Hasegawa (1990). Królikowska (2014) determined the original and future orbits upon completing a redetermination of the comet’s orbit. She said the original orbit was elliptical with a period of about 3.3 million years, while the future orbit was hyperbolic with an eccentricity of 1.00003. T ω Ω (2000.0) i q e 1986 Nov. 17.1043 (TT) 16.9957 268.3259 132.4743 5.457518 1.002842

absolute magnitude: H10 = 5 (Meyer) full moon: 1987 Apr. 14, May 13, Jun. 11, Jul. 11, Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2, Mar. 3, Apr. 2, May 1, May 31, Jun. 29, Jul. 29, Aug. 27, Sep. 25, Oct. 25, Nov. 23, Dec. 23, 1989 Jan. 21, Feb. 20, Mar. 22, Apr. 21, May 20, Jun. 19, Jul. 18, Aug. 17, Sep. 15, Oct. 14, Nov. 13, Dec. 12, 1990 Jan. 11, Feb. 9, Mar. 11, Apr. 10, May 9, Jun. 8, Jul. 8, Aug. 6, Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30, Apr. 28, May 28, Jun. 27, Jul. 26, Aug. 25, Sep. 23, Oct. 23, Nov. 21, Dec. 21, 1992 Jan. 19 sources: C. S. Shoemaker, E. M. Shoemaker, and B. A. Skiff, IAUC, No. 4384 (1987 May 5); B. A. Skiff and D. W. E. Green, MPC, Nos. 11783, 11831 (1987 May 13); D. W. E. Green, IAUC, No. 4395 (1987 May 18); T. Gehrels and J. V. Scotti, ICQ, 9 (1987 Jul.), p. 113; T. Seki, T. Kojima, S. Ueda, T. Gehrels, J. V. Scotti, J. W. Briggs, and D. W. E. Green, MPC, Nos. 11895–6, 12008 (1987 Jul. 11); J. B. Gibson, MPC, No. 12033 (1987 Aug. 9); D. W. E. Green, MPC, No. 12704 (1988 Jan. 4); J. V. Scotti, MPC, Nos. 12856, 12865 (1988 Apr. 2); J. V. Scotti, MPC, Nos. 13003, 13007 (1988 May 1); D. W. E. Green, MPC, No. 13458 (1988 Aug. 27); K. J. Meech and D. W. E. Green, MPC, Nos. 13782, 13843 (1988 Nov. 23); S. Yabushita and I. Hasegawa, The Observatory, 109 (1989 Oct.), p. 189; D. W. E. Green, MPC, No. 16377 (1990 Jun. 8); S. Yabushita and I. Hasegawa, The Observatory, 110 (1990 Dec.), p. 196; K. J. Meech correspondence with G. W. Kronk (1994); K. J. Meech, 290

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O. R. Hainaut, and B. G. Marsden, Icarus, 170 (2004), pp. 463–91; M. Królikowska, AAP, 567 (2014 Jul.), A126, 31pp. 19P/Borrelly Recovered: 1987 June 5.73 (Δ = 2.39 AU, r = 2.44 AU, Elong. = 81
) Last seen: 1988 May 19.30 (Δ = 2.28 AU, r = 2.13 AU, Elong. = 68
) 1987 Closest to the Earth: 1987 December 6 (0.4822 AU) XXXIII=1987p Calculated path: SCL (Rec), FOR (Jul. 12), ERI (Sep. 20), FOR (Oct. 24), ERI (Nov. 22), CET (Nov. 27), ARI (Dec. 23), TRI (1988 Jan. 14), PER (Jan. 18), AUR (Mar. 5), CAM (Mar. 8), AUR (Mar. 10), LYN (Apr. 3), UMa (May 8), LYN (May 16) S. Nakano (1985, 1986) took 45 positions from the apparitions spanning 1960 to 1981, included planetary perturbations, and solved for nongravitational effects. He predicted the comet would next arrive at perihelion on 1987 December 18.33. The comet was recovered on 1987 June 5.73, when A. C. Gilmore and P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) located it on a 45-minute exposure acquired with a 61-cm reflector. The position was α = 0h 35.5m, δ = 28
520 (2000). The comet was also located on exposures of 50 and 80 minutes that were acquired with the same telescope on June 5.76 and June 7.75, respectively. For both the 5th and 7th, Gilmore and Kilmartin estimated the nuclear magnitude as 19, and described the comet as diffuse, with a condensation. The comet moved slightly northward following its recovery, but after attaining a declination of 28.8
on June 17 it began a southward motion. The next observations of this comet were visual ones made on July 25 by M. L. Clark and A. R. Pearce (Perth, Western Australia, Australia). Clark was using his 31-cm reflector and gave the magnitude as 13.7, while Pearce was using his 32-cm reflector and gave the magnitude as 13.8. Both observers reported a very slightly condensed coma that was 0.50 across. The comet was only detected from two locations in August. Astronomers at Perth Observatory (Western Australia, Australia) photographed the comet on the 17th, 18th, and 26th, but provided no descriptions. A. Hale (Las Cruces, New Mexico, USA) visually spotted the comet on the 28th. Using his 41-cm reflector, he judged the magnitude as 12.5. The comet brightened during September. Clark reported magnitudes of 11.0, 10.8, and 10.4 on the 2nd, 17th, and 27th, respectively. He added that the coma was moderately condensed and 2–30 across. Pearce reported the magnitude remained at 10.8 during the 27th to the 30th. He also reported a moderately condensed coma, but gave diameters of 2–2.50 . A. F. A. L. Jones (Stoke, New Zealand) saw the comet on six nights from the 23rd to the 30th. He appears to have only noted the central condensation of the comet with his 32-cm reflector, giving the “coma” diameter as 0.5–1.00 . Jones reported that the magnitude increased from 12.9 to 12.0 during this period. 291

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The comet continued to brighten during October. Hale and R. A. Keen (Mt. Thorodin, Colorado, USA) saw the comet on the 1st. Both determined the magnitude as 11.3. Keen was using his 32-cm reflector and noted a slightly condensed coma 10 across. The comet attained its most southerly declination of 39
on October 12. On that same night, D. A. J. Seargent (The Entrance, New South Wales, Australia) saw the comet using his 25-cm reflector. He gave the magnitude as 10.4 and reported a moderately condensed coma 20 across. Hale judged the magnitude as 10.2 on the 16th. Pearce and Seargent independently observed the comet on the 17th, giving the magnitude as 9.6 and 9.3, respectively. Pearce was using his 20-cm reflector and noted a moderately condensed coma 3.50 across. On the 22nd and 23rd, Pearce determined the comet’s magnitude as 9.5. He said the coma was still moderately condensed, but with a diameter of 30 . On the 26th, Hale determined the magnitude as 9.4. Seargent saw the comet using his 15  80 binoculars on the 27th, giving the magnitude as 8.7 and estimating the coma diameter as 80 . The comet continued to slowly brighten during November. Seargent made a fine series of observations using his 15  80 binoculars, which indicated the comet brightened from 8.2 to 7.1 during the period of the 8th to the 25th. He continually noted a moderately condensed coma, the diameter of which increased from 60 to 120 . J. V. Scotti (Kitt Peak, Arizona, USA) observed the comet using 10  50 binoculars during the 15th to the 24th, indicating that it brightened from 7.9 to 7.6. He said the coma varied from slightly to moderately condensed. A. Boattini (Piazzano, Italy) observed a tail 80 long using his 40-cm reflector on the 15th and a tail extending 70 in PA 167
using his 33-cm reflector on the 18th. G. S. Keitch (Wrington, England) saw the comet using 20  80 binoculars on the 22nd and said the tail extended 100 in PA 134
. C. S. Morris (Whitaker Peak, California, USA) observed the comet on the 26th using his 26-cm reflector and noted a tail extending 400 in PA 180
. The comet reached a maximum elongation of 134
on November 29. Observers indicated the comet was at its brightest around midDecember. A. Ishikawa (Japan) saw the comet on 17 nights with his 13-cm reflector during the 2nd to the 31st. He gave the magnitude as 8.5 on the 2nd, magnitude 7.8–8.1 during the 15th to the 26th, and 8.3 on the 31st. A. Nakamura (Kuma, Ehime, Japan) observed the comet using his 20-cm reflector during the 1st to the 26th. He gave the magnitude as 8.1 on the 1st, 7.6–7.7 during the 14th to the 19th, and 7.8 on the 26th. J. E. Bortle (Stormville, New York, USA) observed the comet using 10  50 binoculars during the 9th to the 24th. He gave the magnitude as 7.5 on the 9th, 7.1–7.3 during the 13th to the 22nd, and 7.4 on the 24th. Most observers noted a moderately condensed coma that was 3–50 across at the beginning of the month, 9–140 across around mid-month, and 5–90 across by the end of the month. Bortle reported a tail extending toward PA 90
during the 12th to the 19th and gave the length as 90 on the 19th. C. E. Spratt (Victoria, British Columbia, Canada) used his 11  80 binoculars and reported a tail 292

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extending 100 in PA 60
on the 15th, 17th, and 24th. Boattini noted a tail 50 long in PA 65
on the 20th. The comet faded in 1988 January. The most prolific observer was Ishikawa, who saw the comet on 15 nights during the 1st to the 28th. He said the magnitude faded from 8.0 to 9.6. Pearce said the comet faded from 7.8 to 8.4 during the 7th to the 21st. Bortle noted a fading from 7.6 to 8.8 during the 5th to the 17th. Most observers indicated the comet was moderately condensed early in the month and slightly condensed at the end of the month. The coma diameter seemed to change little during the month, although the size varied depending on observer experience and size of the instrument used to make the observation. Bortle noted diameters of 9–110 from the 5th to the 17th, using 10  50 binoculars. Keen gave the diameter as 200 on the 8th, using 8  40 binoculars. Ishikawa noted diameters of 3–50 during the entire month while using his 13-cm reflector. Pearce noted diameters of 2.5–40 during the month, as seen through his 20-cm reflector. Ishikawa said the tail was 50 long on the 10th and 11th. Nakamura said the tail extended toward PA 100
on the 10th, and PA 90
on the 13th and 23rd. Observations dwindled in February as the comet continued to fade. Ishikawa was again the most prolific observer, as he saw the comet on nine nights during the 3rd to the 21st. He said the magnitude faded from 9.8 to 10.6. Ishikawa added that the coma was 2–30 across, while it remained slightly condensed. Morris reported that the magnitude faded from 9.1 to 9.6 from the 8th to the 16th. His 20  80 binoculars revealed a very slightly condensed coma 9–130 across. Bortle began using his 32-cm reflector to make observations and noted the comet’s magnitude varied from 9.5 to 9.7 during the 7th to the 22nd, with no clear sign of fading. The coma remained slightly to moderately condensed and 2.7–3.60 across. S. Garro (France) observed the comet using his 20-cm reflector on the 13th and noted tails extending 30 in PA 137
, 20 in PA 51
, 40 in PA 108
, and 20 in PA 142
. The number of observations was greatly reduced during March, as the comet’s faintness required larger telescopes. Most observers described the coma as only slightly condensed and 2–30 across. Bortle saw the comet on the 6th with his 32-cm reflector. He estimated the magnitude as 10. Hale and R. J. Bouma (Groningen, Netherlands) saw the comet on the 7th, both giving the magnitude as 10.5. Hale was using his 41-cm reflector, while Bouma was using his 25-cm reflector. On the 8th, the magnitude was given as 10.7 by Bouma and 10.9 by Bortle. Bortle’s next observation came on the 12th, when he gave the magnitude as 11.0. On the 13th, Hale gave the magnitude as 11.2. Bouma gave the magnitude as 11.2 on the 17th. Bortle and Hale gave the magnitude as 11.0 and 11.3, respectively, on the 20th. The comet attained its most northerly declination of +54
on March 24. The comet was last visually detected in April. Hale gave the magnitude as 12.1 on the 5th. D. H. Levy (Catalina Station, Mt. Bigelow, Arizona, USA) saw the comet using the 154-cm reflector on the 9th. He gave the magnitude as 12.4 and noted a strongly condensed coma about 20 across. Levy added 293

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that he detected a tail extending 50 toward PA 350
. Keen observed the comet with his 32-cm reflector on the 12th, giving the magnitude as 11.8. He noted a very slightly condensed coma 1.50 across. Hale made the final visual observation on April 19, giving the magnitude as 12.6. The comet was last detected during May 19.28–19.30, when K. J. Meech (Mauna Kea, Hawaii, USA) acquired three CCD images totaling 1350 seconds using the 224-cm reflector. The position was α = 9h 02.4m, δ = +45
510 (2000). No physical description was provided. Multiple apparition orbits have been calculated by K. Muraoka (1992), Nakano (1998, 2005, 2012), K. Kinoshita (2000, 2001, 2003), and P. Rocher (2000, 2001). All of these calculations included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of December 18.32 and a period of 6.86 years. The nongravitational terms were within the following ranges: A1 = +0.12 to +0.22 and A2 = 0.0492 to 0.0376. The orbit of Nakano (2005) is given below. T ω Ω (2000.0) i q e 1987 Dec. 18.3235 (TT) 353.3367 75.4331 30.3255 1.356796 0.624211

absolute magnitude: pre-perihelion: H0 = 6.1, n = 9.8, post-perihelion: H0 = 7.0, n = 6.6, from visual observations (Meyer) full moon: 1987 May 13, Jun. 11, Jul. 11, Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2, Mar. 3, Apr. 2, May 1, May 31 sources: S. Nakano, Nakano Note, No. 486 (1985 Dec. 22); S. Nakano, MPC, No. 10522 (1986 Mar. 26); A. C. Gilmore and P. M. Kilmartin, IAUC, No. 4404 (1987 Jun. 8); A. C. Gilmore and P. M. Kilmartin, MPC, No. 11895 (1987 Jul. 11); A. R. Pearce and M. L. Clark, IAUC, No. 4426 (1987 Jul. 30); A. Hale, IAUC, No. 4453 (1987 Sep. 24); M. L. Clark, A. R. Pearce, A. Hale, R. A. Keen, and A. F. A. L. Jones, ICQ, 9 (1987 Oct.), p. 169; A. F. A. L. Jones, R. A. Keen, A. Hale, and D. A. J. Seargent, IAUC, No. 4480 (1987 Oct. 27); [Perth], MPC, No. 12362 (1987 Nov. 5); D. A. J. Seargent, A. Boattini, J. V. Scotti, IAUC, No. 4492 (1987 Nov. 19); A. Hale, IAUC, No. 4512 (1987 Dec. 14); G. J. Garradd and A. Boattini, IAUC, No. 4520 (1987 Dec. 27); D. A. J. Seargent, J. V. Scotti, M. L. Clark, A. Hale, C. E. Spratt, and A. R. Pearce, ICQ, 10 (1988 Jan.), pp. 23–7; C. E. Spratt, IAUC, No. 4527 (1988 Jan. 12); C. S. Morris, IAUC, No. 4537 (1988 Jan. 27); J. E. Bortle, C. S. Morris, and A. Hale, IAUC, No. 4560 (1988 Mar. 8); A. Boattini, C. E. Spratt, J. E. Bortle, R. J. Bouma, A. Hale, and A. R. Pearce, ICQ, 10 (1988 Apr.), pp. 51–4; J. E. Bortle and A. Hale, IAUC, No. 4581 (1988 Apr. 15); D. H. Levy, R. A. Keen, and A. Hale, IAUC, No. 4611 (1988 Jun. 11); S. Garro and R. J. Bouma, ICQ, 10 (1988 Jul.), pp. 67, 87–9; K. J. Meech, MPC, No. 13360 (1988 Aug. 27); C. S. Morris, ICQ, 10 (1988 Oct.), p. 121; C. S. Morris and R. A. Keen, ICQ, 11 (1989 Jan.), pp. 9, 22–3; G. S. Keitch, A. Ishikawa, and A. Nakamura, ICQ, 12 (1990 Oct.), pp. 165–6; K. Muraoka, CCO, 7th ed. (1992), pp. 32, 67, 74; K. J. Meech correspondence 294

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with G. W. Kronk (1994); S. Nakano, Nakano Note, No. 683 (1998 May 2); K. Kinoshita correspondence with G. W. Kronk (2000, 2001, 2003); P. Rocher correspondence with G. W. Kronk (2000, 2001); S. Nakano, Nakano Note, No. 1205 (2005 Jul. 4); S. Nakano, Nakano Note, No. 2302 (2012 Jul. 29). 89P/1987 N1 Recovered: 1987 July 1.79 (Δ = 1.20 AU, r = 2.15 AU, Elong. = 153
) (Russell 2) Last seen: 1987 August 28.63 (Δ = 1.37 AU, r = 2.19 AU, Elong. = 134
) Closest to the Earth: 1987 July 15 (1.1772 AU) 1987 XI=1987q Calculated path: SGR (Rec) [Did not leave this constellation] Predictions for the return of this comet were published by S. Nakano (1985) and S. W. Milbourn (1986). Nakano took six positions from the 1980 apparition, included perturbations by Mercury to Pluto, and integrated the motion to reveal the next perihelion date as 1987 July 1.71. Milbourn (1986) took the orbit B. G. Marsden calculated for the 1980 apparition and integrated it to this apparition using perturbations by all nine planets. He determined the perihelion date as July 4.38. M. P. Candy found this comet on plates exposed by P. Jekabsons and J. Johnston (Perth Observatory, Bickley, Western Australia, Australia) on 1987 July 1.79, July 2.70, and July 2.80. The position on the first date was α = 20h 21.5m, δ = 40
420 (2000). Candy described it as nearly stellar, with a nuclear magnitude of about 20. Perth Observatory and Siding Spring Observatory (New South Wales, Australia) acquired only a few observations during July. C. M. Humphries and R. W. Wilson (Siding Spring Observatory) photographed the comet using the 122-cm Schmidt telescope on the 4th and estimated the magnitude as 18. They noted a strongly condensed nucleus within a coma 1000 in diameter. There was also a diffuse tail extending 0.40 in PA 250
. A photograph by Jekabsons and Johnston on the 6th revealed the comet was nearly stellar. Candy, Jekabsons, and Johnston acquired additional photographs on the 18th, 24th, and 31st, but no descriptive information was provided. The comet reached a maximum elongation of 158
on July 17. The comet moved southward following its recovery, but after attaining a declination of 43
on August 2, it began a slow northward motion. Candy, Jekabsons, and Johnston photographed the comet on August 18, while A. C. Gilmore (Mt. John University Observatory, Lake Tekapo, New Zealand) acquired two photographs on August 19. No physical descriptions were provided. The comet was last detected on August 28.63, when it was photographed by Candy, Jekabsons, and Johnson. No physical description was provided, but the position was α = 19h 53.3m, δ = 41
320 (2000). Multiple apparition orbits have been calculated by Nakano (1987, 1999, 2006), G. V. Williams (1999), and K. Kinoshita (2003, 2009). All of these calculations included full planetary perturbations, but Kinoshita (2009) was the only one to solve for nongravitational effects. The result was a 295

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perihelion date of July 3.73–3.75 and a period of 7.10 years. The nongravitational terms were given as A1 = +1.06 and A2 = 0.0313 by Kinoshita (2009). The orbit of Kinoshita (2009) is given below. T ω Ω (2000.0) i q e 1987 Jul. 3.7456 (TT) 245.3930 45.1099 12.5341 2.151363 0.417811

absolute magnitude: H10 = 14.3 (Meyer) full moon: 1987 Jun. 11, Jul. 11, Aug. 9, Sep. 7 sources: S. Nakano, Nakano Note, No. 474 (1985 Jul. 7); S. W. Milbourn, HBAA for 1987 (1986 Oct.), pp. 75–6; M. P. Candy, P. Jekabsons, and J. Johnston, IAUC, No. 4415 (1987 Jul. 7); M. P. Candy, P. Jekabsons, J. Johnston, C. M. Humphries, and R. W. Wilson, MPC, Nos. 12033–4 (1987 Aug. 9); M. P. Candy, P. Jekabsons, and J. Johnston, MPC, No. 12362 (1987 Nov. 5); S. Nakano, Nakano Note, No. 522 (1987 Dec. 10); A. C. Gilmore, MPC, No. 12859 (1988 Apr. 2); G. V. Williams, CCO, 13th ed. (1999), pp. 76–7; S. Nakano, Nakano Note, No. 694 (1999 Oct. 31); K. Kinoshita correspondence with G. W. Kronk (2003, 2009); S. Nakano, Nakano Note, No. 1322 (2006 Apr. 10). 30P/Reinmuth 1 Recovered: 1987 July 22.44 (Δ = 3.27 AU, r = 2.99 AU, Elong. = 65
) Last seen: 1988 April 14.06 (Δ = 2.04 AU, r = 1.88 AU, Elong. = 67
) 1988 VI=1987r Closest to the Earth: 1987 December 18 (1.3089 AU) Calculated path: TAU (Rec), ORI (Sep. 29), TAU (Nov. 12), GEM (Apr. 11) This comet passed 0.98 AU from Jupiter during 1986 June 24, which decreased the perihelion distance from 1.98 AU to 1.87 AU and decreased the period from 7.59 to 7.29 years. B. G. Marsden (1986) calculated an orbit using positions spanning the period of 1928 to 1973, included perturbations by all nine planets, and solved for nongravitational effects. He then integrated the comet’s motion to this apparition and predicted it would next arrive at perihelion on 1988 May 9.97. T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) recovered this comet on five CCD images acquired with the 91-cm reflector during 1987 July 22.44–22.48. They described the comet as very slightly diffuse, with a coma about 1500 across, and a possible tail in PA 260
. The comet was at α = 3h 35.1m, δ = +11
410 (2000) on the first image, but Gehrels and Scotti noted there was a “poor set of reference stars owing to twilight interference” for all five images. Gehrels and Scotti confirmed the recovery during July 23.44–23.46 and determined the magnitude as 19.6. An independent confirmation came from J. B. Gibson (Palomar Observatory, California, USA), when he acquired two CCD images on July 25.46, using the 152-cm reflector. No physical description was provided. The comet was followed by only a few observatories during the remainder of 1987. Gehrels and Scotti acquired images on August 17, which 296

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indicated the comet was magnitude 19.6, with a weak, moderately condensed coma. The comet had moved northward since its recovery and reached a declination of +13
on September 4. It then began moving southward. Gehrels and Scotti acquired images on September 27, which indicated a magnitude of 18.3 and a nuclear magnitude of 19.7. They noted a tail extending 3000 toward PA 262
. K. Endate and T. Fujii (Kitami, Hokkaido, Japan) photographed the comet on November 28, but provided no physical description. The comet reached a maximum elongation of 169
on November 30. After having moved southward since early September, the comet attained a declination of +11
on December 1 and then began a northward motion. R. E. McCrosky (Oak Ridge Observatory, Massachusetts, USA) obtained a 30-minute exposure using the 155-cm reflector on December 18, but did not provide a physical description. D. H. Levy (Catalina Station, Mt. Bigelow, Arizona, USA) saw the comet using the 154-cm reflector on December 21 and estimated the magnitude as 13.5. He noted a slightly condensed coma. Also on the 21st, Scotti acquired images of the comet that revealed a magnitude of about 16 and a nuclear magnitude of 18.7. He added that the coma was 0.780 across. The comet was widely observed during the early months of 1988, when it was expected to be at its brightest. The first physical description of the year came from Lowell Observatory. During a routine survey with the 33-cm photographic telescope at Lowell Observatory’s Anderson Mesa Station (Arizona, USA), B. A. Skiff exposed photographic plates on January 15, which held the images of eight moving objects. E. L. G. Bowell discovered the objects, and S. McDonald and D. Norman measured their positions. The details were forwarded to the Minor Planet Center. On Minor Planet Circular number 12853, it was announced that S. Nakano identified one of these minor planets (designated 1988 AH) as periodic comet 30P/Reinmuth 1. It was described as stellar and magnitude 16.8. A few physical descriptions were reported during the remainder of January and into March. T. Kojima (Chiyoda, Gunma, Japan) photographed the comet on January 23, February 10, February 19, and March 12, using a 25-cm reflector, and consistently estimated the magnitude as 16. Scotti acquired images on February 13, noting the magnitude as 16.4 and the nuclear magnitude as 19.1. He added that a tail extended 1.40 in PA 80
. Scotti acquired additional images on March 14, which revealed a nuclear magnitude of 18.7. He said the tail extended 6400 toward PA 88
. The comet was last detected on April 14.06, when McCrosky (Oak Ridge Observatory) obtained a 59-minute exposure using the 155-cm reflector. The comet was at α = 6h 05.8m, δ = +23
330 (2000). No physical description was provided. Aside from Levy’s observation using a 154-cm reflector, no other visual observations were made during this apparition; however, it is well documented that A. Hale (New Mexico, USA), a very experienced comet observer, did try to visually observe the comet on 13 occasions during the period 297

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of 1987 October 19 to 1988 May 13 using his 41-cm reflector. Although he never spotted the comet, his observations were made during the period when the comet should have been at its brightest and indicate that it remained fainter than magnitude 13.0–14.0. Multiple apparition orbits have been calculated by Marsden (1993, 1997), K. Kinoshita (1998, 2003, 2004, 2010), S. Nakano (2003, 2014), and P. Rocher (2004, 2006). All of these included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of May 9.98–9.99 and a period of 7.29 years. The nongravitational terms were within the following ranges: A1 = +0.07 to +0.33 and A2 = 0.0157 to 0.0116. The orbit of Rocher (2006) is given below. T ω Ω (2000.0) i q e 1988 May 9.9854 (TT) 13.0579 119.8079 8.1347 1.869283 0.503013

absolute magnitude: H10 = 9.4, from single visual observation, H0 = 11.2, n = 5.1, from non-visual observations (Meyer) full moon: 1987 Jul. 11, Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2, Mar. 3, Apr. 2, May 1 sources: B. G. Marsden, MPC, No. 10524 (1986 Mar. 26); R. E. McCrosky, HOPL (1987–8); T. Gehrels and J. V. Scotti, IAUC, No. 4424 (1987 Jul. 24); T. Gehrels, J. V. Scotti, and J. B. Gibson, MPC, No. 12034 (1987 Aug. 9); T. Gehrels and J. V. Scotti, MPC, Nos. 12169–70 (1987 Sep. 7); T. Gehrels and J. V. Scotti, ICQ, 9 (1987 Oct.), p. 170; T. Gehrels and J. V. Scotti, MPC, Nos. 12362, 12365 (1987 Nov. 5); A. Hale, D. H. Levy, T. Gehrels, and J. V. Scotti, ICQ, 10 (1988 Jan.), p. 29; K. Endate, T. Fujii, R. E. McCrosky, J. V. Scotti, B. A. Skiff, E. L. G. Bowell, S. McDonald, and D. Norman, MPC, Nos. 12748, 12771 (1988 Feb. 2); A. Hale, ICQ, 10 (1988 Apr.), p. 56; S. Nakano, T. Kojima, and J. V. Scotti, MPC, Nos. 12853, 12859–60, 12865 (1988 Apr. 2); T. Kojima, MPC, No. 13005 (1988 May 1); R. E. McCrosky, MPC, No. 13110 (1988 May 31); A. Hale, ICQ, 10 (1988 Jul.), p. 89; B. G. Marsden, CCO, 8th ed. (1993), pp. 34, 69, 76; B. G. Marsden, CCO, 12th ed. (1997), pp. 58–9; K. Kinoshita correspondence with G. W. Kronk (1998, 2003, 2004, 2010); S. Nakano, Nakano Note, No. 1011 (2003 Dec. 8); P. Rocher correspondence with G. W. Kronk (2004, 2006); S. Nakano, Nakano Note, No. 2729 (2014 Jun. 25); B. A. Skiff correspondence with G. W. Kronk (2014). C/1987 P1 Discovered: 1987 August 11.44 (Δ = 1.57 AU, r = 1.72 AU, Elong. = 81
) (Bradfield) Last seen: 1988 April 13.87 (Δ = 3.15 AU, r = 2.62 AU, Elong. = 50
) Closest to the Earth: 1987 December 12 (0.8337 AU) 1987 Calculated path: HYA (Disc), VIR (Aug. 15), LIB (Aug. 18), SCO (Oct. 4), XXIX=1987s OPH (Oct. 11), SER (Nov. 13), OPH (Nov. 14), AQL (Nov. 18), SGE (Dec. 2), DEL (Dec. 5), VUL (Dec. 9), PEG (Dec. 14), AND (1988 Jan. 7), PSC (Jan. 14), ARI (Jan. 27), TAU (Mar. 2) 298

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In the course of W. A. Bradfield (Dernancourt, South Australia, Australia) planning his next comet hunting session, he noted that the evening of 1987 August 11 would offer 46 minutes of dark sky between astronomical twilight and moonrise. Although the following days would offer longer periods of comet hunting, several days of cloudy weather were predicted, so he decided to observe on August 11. He drove to an area north of Adelaide and began sweeping with his 15-cm refractor, covering parts of Virgo, Libra, and Hydra. The moon rose above the eastern horizon around 8:00 p.m. local time, but he decided to make a few more sweeps. Shortly thereafter, on August 11.44, he detected a comet in Hydra and observed it for about an hour for signs of motion. No motion was detected because some of the faint nearby stars had been washed out by moonlight. Bradfield gave the position as α = 14h 13.3m, δ = 23
350 (2000). He estimated the magnitude as 10, and described the comet as diffuse, with no condensation. Knowing that cloudy weather was going to prevail in his area for the next few days, Bradfield called D. A. J. Seargent (The Entrance, New South Wales, Australia) the next morning and told him of his new discovery. Seargent then alerted several other observers to help confirm the comet. Several independent confirmations were made on August 12. A. C. Gilmore and P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) photographed the comet on August 12.34. They estimated the magnitude as 9, and said the comet was moderately condensed. On August 12.35, Gilmore visually observed the comet using a 10-cm reflector and determined the magnitude as 9.3. He said the coma was 50 across. R. H. McNaught (Siding Spring Observatory, New South Wales, Australia) photographed the comet with the 51-cm Uppsala Southern Schmidt telescope on August 12.39. He estimated the magnitude as 8.5, and said the comet exhibited a strong condensation. McNaught also noted a diffuse tail extending 50 in PA 110
. T. Lovejoy (Shailer Park, near Brisbane, Queensland, Australia) visually observed the comet on August 12.44, using a 20-cm reflector, and estimated the magnitude as 9. The comet was well followed during the remainder of August, especially by observers in the Southern Hemisphere. The most prolific observers were Lovejoy, who saw the comet on nine nights spanning the 14th to the 31st, G. J. Garradd (Tamworth, New South Wales, Australia), who saw the comet on eight nights spanning the 15th to the 29th, and A. R. Pearce (Woodlands, Western Australia, Australia), who saw the comet on seven nights spanning the 13th to the 28th. All three observers indicated that the comet brightened as August progressed, with the magnitude ranges being given as 9.0 to 7.8 by Lovejoy (15  80 binoculars and 20-cm reflector), 9.3 to 8.2 by Garradd (15-cm reflector, 20-cm reflector, and two pairs of binoculars), and 9.0 to 8.6 by Pearce (13-cm refractor). Pearce also noted a starlike nucleus of magnitude 10.5 on the 13th and said the comet exhibited a “parabolic head” and a “quite broad” tail on the 16th. These observers also noted the coma remained moderately condensed, with a diameter that 299

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generally increased from about 2.50 to 60 . Another Southern Hemisphere observer, M. L. Clark (Perth, Western Australia, Australia), obtained a nice series of measurements of the tail using his 31-cm reflector. He noted it extended 50 in PA 114
on the 13th, 100 in PA 116
on the 15th, 70 in PA 116
on the 16th, 110 in PA 116
on the 19th, and 330 in PA 119
on the 26th. The comet continued to brighten in September and remained moderately condensed. Garradd saw the comet on nine nights spanning the 10th to the 25th, giving the magnitude as 7.6 on the first date and 6.7 on the last. He gave the coma diameter as 80 on the 10th and 50 during the 11th–13th. Also on the 10th, Garradd said the tail extended 150 in PA 120
. Seargent saw the comet on eight nights from the 10th to the 28th using 15  80 binoculars. He gave the magnitude as 7.8 on the first night and 6.7 on the last. Seargent also indicated that the coma diameter increased from 40 on the 10th to 70 by the 23rd. He noted that the tail extended about 120 in PA 100
on the 11th and 360 in PA 115
on the 23rd. E. P. Moore and D. A. Klinglesmith (Joint Observatory for Cometary Research, New Mexico, USA) obtained 10-minute exposures of this comet on four nights using the 35-cm Schmidt telescope. Their measurements indicated the tail extended 150 in PA 115
on the 12th, 200 in PA 116
on the 13th, 200 in PA 110
on the 20th, and 200 in PA 109
on the 21st. The comet was widely observed by Northern Hemisphere observers in October, as the coma became more condensed. J. E. Bortle (Stormville, New York, USA) followed the comet from the 9th to the 31st, using his 10  50 binoculars. He reported the magnitude brightened from 6.3 to 5.6. During this same period, Bortle said the coma diameter increased from 4.50 to 60 . Using his 32-cm reflector, he also gave measurements of the tail, noting that it extended 0.5
in PA 100
on the 13th and 270 in PA 95
on the 22nd. R. A. Keen (Mt. Thorodin, Colorado, USA) observed the comet using 8  40 binoculars from the 4th to the 28th. He indicated the comet brightened from magnitude 7.1 to 5.9, while the coma diameter increased from 30 to 60 . From the 17th to the 28th, he noted the tail consistently extended toward PA 90
and increased in length from 160 to 0.6
. J. D. Shanklin (Cambridge Observatory, England) followed the comet from the 6th to the 25th, using 20  80 binoculars. He indicated that the comet brightened from 7.3 to 6.1, while the coma diameter increased from about 20 to 40 . Shanklin said the 20-cm refractor revealed a tail extending 470 in PA 102
on the 12th. Keen was also the first person to spot the comet with the naked eye, when he gave the magnitude as 6.2 on the 19th. J. V. Scotti (Tucson, Arizona, USA) saw the comet with the naked eye on the 20th, giving the magnitude as 6.1. Scotti also noted a tail extending >3
while using 10  50 binoculars. The comet reached a minimum elongation of 48
on October 22. As the comet passed perihelion early in November, amateur astronomers from around the world reported more than 600 observations. A. J. S. Pereira (Linda-A-Velha, Portugal) saw the comet on 15 nights using 9  34 binoculars. He indicated that the magnitude brightened from 5.9 on the 7th to 5.3 300

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by the 28th. Pereira gave coma diameters that varied from 3.50 to 8.50 and reported tail lengths of 0.4
to 3
that extended toward PA 55
to PA 75
. Keen saw the comet on 14 nights, mostly using 8  40 binoculars. He reported that the magnitude brightened from 5.7 on the 3rd, to 5.2 during the 20th to the 24th, and then faded to 5.6 by the 29th. He also reported that he saw the comet on seven nights with the naked eye, with the brightest magnitude being 5.1 on the 22nd. Keen noted the coma was strongly condensed and 4–60 across early in the month and moderately condensed and 9–110 across late in the month. The tail was 2–4
long from the 19th to the 29th and wavered between PA 55
and 65
. A. Ishikawa (Japan) also saw the comet on 14 nights, using his 13-cm reflector. He indicated that the comet was magnitude 6.0 on the 5th, brightened to 5.4 by the 22nd, and faded to 5.8 by the 29th. He noted that the coma remained moderately condensed and 4–60 across during the entire month, while the tail length was variously given as 100 to 1
. Several observers reported naked-eye observations from the 9th to the 24th. Three observers reported the tail was visible to the naked eye during the 20th to the 22nd. Keen, A. Hale (Las Cruces, New Mexico, USA), and M. V. Zanotta (near Como, Italy) measured the tail as extending 1.5–2
in PA 60–65
on the 20th. On the 21st, Keen said the tail extended 4
in PA 60
, while Zanotta said it extended 1.5
in PA 65
. Keen reported that the tail extended 3
in PA 55
on the 22nd. The comet seemed to change little in brightness in December, passing closest to Earth around mid-month. Ishikawa saw the comet on 21 nights spanning the entire month while using his 13-cm reflector. Although his observations indicate the comet faded from magnitude 5.8 on the 1st to 6.5 by the 31st, he implied variations of up to 0.4 magnitude from one night to the next. Ishikawa said the coma basically remained moderately condensed, with a diameter that fluctuated from 40 to 90 . He also indicated that the tail varied from 100 to 1
during the month. Bortle saw the comet during the 2nd to the 30th, using the 10  50 binoculars. He indicated that the brightness varied from 5.7 to 6.2, while the coma remained moderately condensed and 6.50 to 9.50 across. With these same binoculars, Bortle also measured the tail as extending 1
in PA 55
on the 2nd, 3
in PA 58
on the 13th, 3
in PA 55
on the 23rd, and 1.7
in PA 62
on the 27th. Hale saw the comet using 10  50 binoculars and reported the magnitude faded from 5.5 on the 4th to 6.2 by the 28th. He measured the tail as extending 3
in PA 58
on the 9th, 2
in PA 62
on the 21st, 2
in PA 61
on the 24th, and 2
in PA 65
on the 28th. Shanklin saw the comet with 10  80 binoculars on the 7th and reported a broad tail, which spanned an angle of 40
and extended 1.8
in PA 81
. Twelve observers reported a total of 17 naked-eye observations during the period spanning the 9th to the 24th. An antitail was also detected in December. G. Klaus (Grenchenberg, Switzerland) had taken photographs using a 30-cm Schmidt telescope. J.-C. Merlin (Le Creusot, France) measured the photographs and said the antitail extended 350 in PA 224
on the 13th and 700 in PA 241
on the 21st. 301

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D. Ketelsen (Catalina Station, Mt. Bigelow, Arizona, USA) obtained 30-minute exposures of the comet using the 43-cm Schmidt telescope on the 21st and 22nd. On both nights, the antitail extended 1
in PA 240
, while the main tail was >3.7
long. Ketelsen added that the antitail was better defined on the second night. C. S. Morris (Whitaker Peak, California, USA) saw the comet with his 26-cm reflector on the 22nd and noted a broad, very faint sunward tail extending 350 in PA 250
. S. Korth (Monheim, Germany) saw the antitail on the 22nd and 23rd. On the first night, he said it extended about 200 in about PA 220
. On the second night, he said it extended about 200 in about PA 230
. D. H. Levy (Tucson, Arizona, USA) observed using an 8-cm refractor on the 23rd and noted a “strong, pointed sunward tail” that was “slightly forked.” It extended 1.5
in PA 240
. The comet faded in 1988 January, no longer being a naked-eye object, and most observers were still reporting it as moderately condensed. Ishikawa saw the comet on 15 nights during the period of the 1st to the 29th, noting the magnitude dropped from 6.7 to 8.2. The coma diameter varied from 4–80 . Ishikawa saw the tail from the 6th to the 18th, noting lengths of 5–120 . Bortle saw the comet from the 4th to the 17th, using 10  50 binoculars, and noted the magnitude faded from 6.2 to 6.8. He gave coma diameters of 80 to 110 . His measurements indicated that the tail extended 1.2
in PA 62
on the 5th, 1
in PA 58
on the 12th, and 450 in PA 62
on the 16th. Bortle added that his 32-cm reflector revealed an “almost stellar nucleus” of the 12th magnitude on the 17th. Morris only saw the comet during the 13th to the 22nd. He reported the magnitude faded from 6.8 to 7.1 and gave coma diameters of 8–100 . He reported the tail extended 4.5
in PA 65
on the 13th, while the antitail extended 400 in PA 270
. Observing with his 26-cm reflector on the 22nd, Morris said the tail extended 1.67
in PA 60
. He added, “There was a faint dust fan extending from the anti-tail, passing through [north] and connecting with the main tail.” He also noted jets and at least one hood near the nucleus. The comet attained its most northerly declination of +26
on January 6 and reached a maximum elongation of 88
on January 16. The number of observations dramatically dropped in February. Ishikawa was again the most prolific observer, as he saw the comet on 17 nights spanning the 1st to the 24th using his 13-cm reflector. He said the comet faded from 8.6 to 9.7, while the slightly condensed coma was 2–50 across. Bortle viewed the comet with his 32-cm reflector and indicated that the magnitude faded from 8.8 to 9.4. His 10  50 binoculars still revealed the coma diameter as 90 on the 7th, while the binoculars revealed diameters of 2.90 to 4.50 during the other nights. Bortle added that the reflector revealed a “tiny stellar nucleus” of the 13th magnitude on the 7th and a tail extending 120 in PA 50
on the 11th. Morris observed the comet using 20  80 binoculars from the 8th to the 16th, noting magnitudes of 8.0–8.2 and coma diameters of 9–110 . He added that the coma was slightly condensed. Morris reported a “straight, narrow, and very faint” tail on the 8th that 302

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extended 2
100 in PA 69
. He said the tail was “much less obvious” on the 10th and extended only about 200 . The tail was still about 200 long on the 16th and extended toward PA 70
. Less than 60 observations were reported for this comet in March. Bortle saw the comet on five nights spanning the 6th to the 20th and reported the magnitude faded from 10.4 to 11.2. He generally noted a very slightly condensed coma that shrank from 4.20 to 2.00 . Ishikawa saw the comet on five nights spanning the 6th to the 18th and noted that it faded from magnitude 9.7 to 10.4. He said the coma was slightly condensed and shrank from 4.00 to 2.00 across. The tail was only reported by two observers: E. A. Jacobson (Evansville, Minnesota, USA) and S. Garro (France). Jacobson saw it on the 5th and 6th, using his 25-cm reflector, noting that it extended 240 in PA 65
on the first night and 260 in PA 63
on the second night. Garro saw the comet on the 9th, using his 20-cm reflector and reported that the tail extended 30 in PA 97
. Jacobson suspected that he saw the tail on the 14th, using 20  80 binoculars. He said it extended about 60 in PA 62
. The last visual observations were acquired in April. Hale saw the comet with his 41-cm reflector on the 5th, giving the magnitude as 10.6 and noting it was “extremely diffuse.” Jacobson was using his 25-cm reflector on the 6th and gave the magnitude as 11.1. Levy (Catalina Station, Mt. Bigelow, Arizona, USA) saw the comet using the 154-cm reflector on the 9th and gave the magnitude as 13.1. The final visual observation came from Jacobson on the 11th. He gave the magnitude as 11.2 and said the coma was very slightly condensed and 2.40 across. The comet was last detected on April 13.87, when it was photographed by Shanklin using a 61-cm Schmidt reflector at Cambridge Observatory and 5-inch by 4-inch Kodak TMax 400 film. The position was α = 4h 52.3m, δ = +20
450 (2000). Shanklin (2015) commented that the comet “isn’t obvious on the April exposure” and probably appeared as “only a faint condensation.” Two observatories observed the visible spectrum. At La Silla Observatory (Chile), H. Böhnhardt observed the comet in late October of 1987, using the 104-cm reflector and IAU cometary filters. He noticed the emissions of diatomic carbon, cyanogen, and triatomic carbon. The same three molecules were also detected by B. S. Rautela and B. B. Sanwal (Uttar Pradesh State Observatory, Nainital, India) when they observed the comet on 1987 November 28, November 30, and December 4. The infrared spectrum was also observed. V. G. Ivanova, B. P. Komitov, S. B. Vladimirov, V. G. Shkodrov, and K. Jockers (Rozhen National Astronomical Observatory, Bulgaria) used a double pass filter and the 70-cm Schmidt telescope on 1988 January 17. They reported that the “red image shows a coma of the [amidyl radical]” and weak emission of ionized water. They added, “The blue image is caused by a neutral molecule, presumably” cyanogen. R. W. Russell, D. K. Lynch, and M. A. Chatelain (1987) obtained infrared observations during November 20–22, using the 152-cm reflector 303

cometography: a catalog of comets

on Mount Lemmon Observatory (Arizona, USA). They detected evidence of silicate emission, with 20% variability. Lynch and R. W. Russell (NASA Infrared Telescope Facility, Mauna Kea, Hawaii, USA) used the 300-cm telescope on December 3–4. They noted silicate emission that varied 10%. They noted that the “color temperature is significantly higher than the equilibrium temperature, suggesting submicron-size grains.” The first parabolic orbit was published by Green on 1987 August 14. He used 10 precise positions obtained during August 12–14, and determined a perihelion date of 1987 November 4.16. B. G. Marsden published parabolic orbits on August 23 and October 7. The first orbit used 19 positions from August 12–22 and gave the perihelion date as November 7.12. The second orbit used 37 positions from August 12 to September 20 and gave the perihelion date as November 7.30. The first elliptical orbit was calculated by Marsden and was published on October 3. This used 50 positions from August 12 to October 1 and included perturbations by all nine planets. The result was a perihelion date of November 7.26 and a period of 2514 years. As additional positions were reported, orbits were published by Marsden on November 5 and T. Kobayashi on 1988 September 25. Both astronomers gave perihelion dates of November 7.27, while the period was given as about 2167 years by Marsden and about 2126 years by Kobayashi. Kobayashi (1989) took 477 positions from the entire apparition and included full planetary perturbations. The result was a perihelion date of November 7.27 and a period of about 2121 years. This orbit is given below. T ω Ω (2000.0) i q e 1987 Nov. 7.2741 (TT) 73.8994 268.0930 34.0882 0.868956 0.994736

absolute magnitude: H0 = 6.0, n = 2.9 (Kronk) full moon: Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2, Mar. 3, Apr. 2, May 1 sources: W. A. Bradfield, A. C. Gilmore, R. H. McNaught, and T. Lovejoy, IAUC, No. 4431 (1987 Aug. 12); A. C. Gilmore, P. M. Kilmartin, and R. H. McNaught, IAUC, No. 4433 (1987 Aug. 13); D. W. E. Green and T. Lovejoy, IAUC, No. 4434 (1987 Aug. 14); B. G. Marsden, IAUC, No. 4442 (1987 Aug. 23); G. J. Garradd, IAUC, No. 4448 (1987 Sep. 15); W. A. Bradfield correspondence with D. E. Machholz (1987 Sep. 18); E. P. Moore and D. A. Klinglesmith, IAUC, No. 4458 (1987 Sep. 29); A. R. Pearce, M. L. Clark, and R. A. Keen, ICQ, 9 (1987 Oct.), pp. 146, 165–7; B. G. Marsden, IAUC, No. 4460 (1987 Oct. 3); B. G. Marsden, MPC, No. 12309 (1987 Oct. 7); R. A. Keen and J. D. Shanklin, IAUC, No. 4466 (1987 Oct. 10); J. V. Scotti and R. A. Keen, IAUC, No. 4477 (1987 Oct. 26); B. G. Marsden and R. A. Keen, IAUC, No. 4483 (1987 Nov. 5); B. G. Marsden, MPC, No. 12440 (1987 Nov. 5); R. W. Russell, D. K. Lynch, M. A. Chatelain, and A. J. S. Pereira, IAUC, No. 4496 (1987 Nov. 24); A. J. S. Pereira, IAUC, No. 4503 304

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(1987 Nov. 27); D. K. Lynch, R. W. Russell, J. D. Shanklin, IAUC, No. 4513 (1987 Dec. 15); D. Ketelsen, IAUC, No. 4518 (1987 Dec. 23); H. Böhnhardt, Astronomische Gesellschaft Abstract Series, No. 1 (1988), p. 8; J. E. Bortle, J. V. Scotti, A. Hale, M. V. Zanotta, and S. Korth, ICQ, 10 (1988 Jan.), pp. 4, 6–19; A. Hale, C. S. Morris, and D. H. Levy, IAUC, No. 4523 (1988 Jan. 1); J.-C. Merlin, G. Klaus, and C. S. Morris, IAUC, No. 4530 (1988 Jan. 16); C. S. Morris, IAUC, No. 4543 (1988 Feb. 4); C. S. Morris, IAUC, No. 4556 (1988 Feb. 26); J. E. Bortle and E. A. Jacobson, IAUC, No. 4566 (1988 Mar. 21); R. A. Keen, A. J. S. Pereira, and J. E. Bortle. ICQ, 10 (1988 Apr.), pp. 37, 42–7; A. Hale, E. A. Jacobson, and D. Levy, IAUC, No. 4582 (1988 Apr. 19); J. D. Shanklin, MPC, No. 13006 (1988 May 1); G. J. Garradd, S. Garro, and A. Hale, ICQ, 10 (1988 Jul.), pp. 70–4; T. Kobayashi, MPC, No. 13597 (1988 Sep. 25); C. S. Morris and E. A. Jacobson, ICQ, 10 (1988 Oct.), pp. 112–16; C. S. Morris, ICQ, 11 (1989 Jan.), pp. 6, 15; T. Lovejoy, ICQ, 11 (1989 Apr.), pp. 31–2; T. Kobayashi, MPC, No. 14903 (1989 Aug. 17); V. G. Ivanova, B. P. Komitov, S. B. Vladimirov, V. G. Shkodrov, and K. Jockers, Asteroids, comets, meteors III; Proceedings of the International Meeting, Uppsala, Sweden, June 12–16, 1989. Uppsala, Sweden (1990), pp. 343–6; A. Ishikawa, ICQ, 12 (1990 Jan.), pp. 6–7; D. H. Levy, ICQ, 13 (1991 Jul.), p. 112; J. D. Shanklin, ICQ, 15 (1993 Oct.), pp. 156–7; J. D. Shanklin correspondence with G. W. Kronk (2015). 58P/Jackson– Recovered: 1987 July 25.48 (Δ = 2.03 AU, r = 1.60 AU, Elong. = 51
) Neujmin Last seen: 1987 September 20.51 (Δ = 1.93 AU, r = 1.95 AU, Elong. = 76
) Closest to the Earth: 1987 December 6 (1.6603 AU) 1987 VIII=1987t Calculated path: ORI (Rec), MON (Sep. 7) S. Nakano (1985, 1986) calculated an orbit for this comet using 14 positions from 1970–1978 and including perturbations by all nine planets. He then integrated the comet’s motion to this apparition and predicted the next perihelion date as 1987 May 24.50. J. B. Gibson (Palomar Observatory, California, USA) recovered this comet on two CCD images acquired with the 152-cm reflector on 1987 July 25.48. He estimated the magnitude as 18. The position was α = 4h 46.5m, δ = +12
520 (2000). T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) independently recovered this comet with the 91-cm reflector and a CCD camera during August 17.48–17.49. Gehrels and Scotti confirmed their recovery on August 18.47. They determined the magnitude as 18.3 and said the coma was 1900 across. The final observations were acquired by Gehrels and Scotti during September 19.49–19.50 and September 20.49–20.51. The 91-cm reflector and CCD camera were again used, but no descriptions were provided. The position on the last image was α = 6h 45.6m, δ = +8
480 (2000). Multiple apparition orbits have been calculated by G. Forti (1989), S. Nakano (1996, 2001), and K. Kinoshita (1998, 2003). These calculations 305

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included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of May 24.52–24.53 and a period of 8.42 years. Although the nongravitational terms were given as A1 = +0.83 and A2 = 0.0042 by Forti and A1 = +0.70 and A2 = 0.0138 by Nakano (1996), Kinoshita (1998, 2003) and Nakano (2001) indicated the terms were within the following ranges: A1 = +0.30 to +0.38 and A2 = 0.0162 to 0.0151. The orbit of Nakano (2001) is given below. T ω Ω (2000.0) i q e 1987 May 24.5253 (TT) 196.6030 163.8161 14.0590 1.437584 0.652563

absolute magnitude: H10 = 14.4 (Meyer) full moon: 1987 Jul. 11, Aug. 9, Sep. 7, Oct. 7 sources: S. Nakano, Nakano Note, No. 473 (1985 Jul. 7); S. Nakano, MPC, No. 10519 (1986 Mar. 26); J. B. Gibson, T. Gehrels, and J. V. Scotti, IAUC, No. 4438 (1987 Aug. 18); J. B. Gibson, T. Gehrels, and J. V. Scotti, MPC, No. 12170 (1987 Sep. 7); T. Gehrels and J. V. Scotti, MPC, No. 12256 (1987 Oct. 7); G. Forti, AAP, 215 (1989), pp. 381–2, 384; S. Nakano, CCO, 11th ed. (1996), pp. 62–3; K. Kinoshita correspondence with G. W. Kronk (1998, 2003); S. Nakano, Nakano Note, No. 778 (2001 Apr. 26). C/1987 Q1 Discovered: 1987 August 21.11 (Δ = 1.27 AU, r = 1.18 AU, Elong. = 61
) (Rudenko) Last seen: 1988 January 25.50 (Δ = 2.14 AU, r = 2.06 AU, Elong. = 72
) Closest to the Earth: 1987 November 20 (0.9143 AU) 1987 Calculated path: BOO (Disc), CVn (Aug. 22), COM (Sep. 8), VIR (Oct. 10), XXIII=1987u LEO (Oct. 24), CRT (Oct. 29), HYA (Nov. 10), ANT (Nov. 13), VEL (Nov. 18), CAR (Nov. 26), VOL (Dec. 2), MEN (Dec. 11), HYI (Dec. 18), HOR (Dec. 28), ERI (1988 Jan. 15) M. Rudenko (Amherst, Massachusetts, USA) discovered this comet with a 15-cm refractor on 1987 August 21.11, at a position of α = 14h 10.2m, δ = +33
460 (2000). He estimated the magnitude as 9.5, and described the comet as diffuse, with slight condensation. The coma was 2–30 across. C. S. Morris (Whitaker Peak, California, USA) confirmed the discovery with a 26-cm reflector on August 21.20. He gave the magnitude as 9.9, and said the comet exhibited no condensation or tail. The comet was well observed during the remainder of August, but there was little indication as to whether the comet was brightening or fading. Most observers continued to describe as it as diffuse, with slight condensation. C. E. Spratt (Victoria, British Columbia, Canada) saw the comet using a 44-cm reflector on the 22nd, giving the magnitude as 9.7 and the coma diameter as 40 . Morris (Lockwood Valley, California, USA) used 20  80 binoculars to view the comet on the 23rd. He gave the magnitude as 9.8 and noted a coma 5’ across. Also on the 23rd, J. B. Gibson (Palomar Observatory, California, USA) photographed the comet using the 46-cm Schmidt 306

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telescope and detected a trail exhibiting a strong condensation within a coma about 4000 wide. Spratt made observations with his 20-cm reflector on the 24th and 25th, when he gave the magnitude as 10.1 and 9.9, respectively. The coma diameter was 30 . On the 26th, D. H. Levy (Amherst, Massachusetts, USA) determined the magnitude as 10.1 while using his 15-cm refractor. A. Hale (Las Cruces, New Mexico, USA) saw the comet using his 20-cm reflector on the 26th and 28th, when he gave the magnitude as about 10.1 and 9.9, respectively. R. J. Bouma (Groningen, Netherlands) used his 25-cm reflector to observe the comet on the 31st. He reported the magnitude as 9.5 and the coma diameter as 2.80 . Bouma added that the coma was elongated and broader toward about PA 155
. The comet brightened in September, but the elongation also decreased, putting the comet in twilight during the last days of the month. E. A. Jacobson (Evansville, Minnesota, USA) was the most prolific observer during the month. Using his 25-cm reflector on 11 nights spanning the 1st to the 26th, he said the magnitude brightened from 9.7 to about 8.2. Jacobson generally noted a slightly condensed coma that was 4.20 to 5.70 across. K. T. Cernis (Moletai, Lithuania) was able to observe the comet on eight nights spanning the 11th to the 22nd while using 20  110 binoculars. The magnitude increased from 9.0 to about 8.0, while the coma was slightly condensed with a diameter of 1.5–20 . The comet reached a minimum elongation of 22
on October 3. No observations were made until the 10th, when H. Hasegawa (Japan) spotted the comet in twilight using his 31-cm reflector. He gave the magnitude as 7.5 and noted a moderately condensed coma 2.50 across. Hale saw the comet using 10  50 binoculars on the 16th and gave the magnitude as 7.6. He also saw it with his 20-cm reflector and noted a tail extending 100 in PA 305
. Hale used his 41-cm reflector on the 21st and 30th, estimating the magnitude as 7.9 and 7.5, respectively. A. Ishikawa (Japan) saw the comet on four nights using his 13-cm reflector. He gave the magnitude as 7.0 and 7.1 on the 17th and 19th, respectively, noting the coma was moderately condensed and 2.50 across on both nights. He gave the magnitude as 7.3 and 6.9 on the 27th and 28th, respectively, and reported a moderately condensed coma that was 30 across, with a tail 100 long. The comet faded in November. In addition, it was becoming more widely observed by observers in the Southern Hemisphere. V. F. de Assis Neto (Sao Francisco de Oliveira, Brazil) saw the comet using 10  70 binoculars on the 1st, giving the magnitude as 7.9 and the coma diameter as 5.60 . Hale saw the comet using 10  50 binoculars on the 3rd and gave the magnitude as 7.8. A. F. A. L. Jones (New Zealand) was the most prolific observer, making seven observations during the 4th to the 30th, mostly using his 8-cm refractor. He indicated that the magnitude faded from 8.0 to 9.9. Using his 32-cm reflector on the 15th, he noted a moderately condensed coma 2.50 across. Three observers reported seeing the tail early in the month. A. Boattini (Italy) saw it on the 3rd, while using his 33-cm reflector, and said 307

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it extended 4
in PA 271
. R. Haver (Italy) observed the comet on the 4th, using 15  80 binoculars, and noted a tail extending 320 in PA 290
. Hasegawa said the tail was 120 long on the 6th. The comet was only visible in the Southern Hemisphere during December, attaining its most southerly declination of 74
on the 13th. Most observers indicated the coma was slightly condensed. M. L. Clark (Australia) saw the comet on the 1st using his 31-cm reflector, giving the magnitude as 8.8 and the coma diameter as 70 . Jones saw the comet on the 11th, using his 8-cm refractor and gave the magnitude as 10.1. Jones and D. A. J. Seargent (The Entrance, New South Wales, Australia) observed the comet on the 13th. Jones was using his 32-cm reflector. He determined the magnitude as 10.4 and said the comet was 20 across. Seargent observed the comet using his 15  80 binoculars and gave the magnitude as 10.0. A. R. Pearce (Australia) used his 20-cm reflector to see the comet on the 14th. He determined the magnitude as 10.0 and reported a coma 3.50 across. Clark and Pearce gave the magnitude as 10.3 and 10.1, respectively, on the 15th. Clark noted a coma 40 across while Pearce said it was 30 across. Clark and Pearce both gave the magnitude as 10.1 on the 16th. The diameter was given as 60 by Clark and 40 by Pearce. Pearce made the final visual observation on the 17th. He gave the magnitude as 10.2 and noted a coma 3.50 across. The comet reached a maximum elongation of 83
on December 18. The comet was last observed during 1988 January. A. C. Gilmore (Mt. John University Observatory, Lake Tekapo, New Zealand) acquired two photographs on January 14; however, although the comet was visible, it was involved with a star. The final observations were acquired on January 25.47 and January 25.50, when Gilmore obtained photographic exposures of 30 and 40 minutes, respectively, using a 61-cm reflector. No descriptive information was provided. The position at the time of the last photograph was α = 2h 08.3m, δ = 52
170 (2000). The first parabolic orbit was calculated by B. G. Marsden and was published on 1987 August 25. He used eight positions from August 22–25 and determined the perihelion date as 1987 October 9.41. As more positions were reported, Marsden published additional parabolic orbits on September 7 and October 3, the latter of which established the perihelion date as October 9.53. The first hyperbolic orbit was calculated by D. W. E. Green and was published on November 5. This used 22 positions from August 22 to October 21 and included full planetary perturbations. The result was a perihelion date of October 9.53 and an eccentricity of 1.00033. T. Kobayashi (1988) took 52 positions from 1987 August 22 to December 19 and included full planetary perturbations. The result was a perihelion date of October 9.53 and an eccentricity of 1.00042. Marsden (1990) calculated original and future orbits for this orbit. The original was found to be elliptical with a period of about 78 thousand years. The future orbit was hyperbolic with an eccentricity of 1.00024. 308

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B. Todorovic-Juchniewicz (1991) took 90 positions from the entire period of visibility and included full planetary perturbations. The result was a hyperbolic orbit with a perihelion date of October 9.53 and an eccentricity of 1.00044. Todorovic-Juchniewicz (1992) also calculated the original and future orbits. The original orbit was elliptical with a period of about 83 thousand years, while the future orbit was hyperbolic with an eccentricity of 1.00025. Although the relatively short observational arc might preclude the calculation of nongravitational effects, Todorovic-Juchniewicz (1992) did calculate an orbit that solved for these terms. He determined them as A1 = +3.46 and A2 = 0.7207. Although the 1992 calculation including nongravitational terms produced better residuals, the author has opted to only present the 1991 gravitational solution below. T ω Ω (2000.0) i q e 1987 Oct. 9.5281 (TT) 143.8336 298.5696 114.8751 0.602603 1.000437

absolute magnitude: H0 = 8.6, n = 3.7 (Kronk) full moon: Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2 sources: M. Rudenko and C. S. Morris, IAUC, No. 4440 (1987 Aug. 21); C. E. Spratt, IAUC, No. 4441 (1987 Aug. 22); B. G. Marsden, C. S. Morris, and C. E. Spratt, IAUC, No. 4443 (1987 Aug. 25); B. G. Marsden, MPC, No. 12201 (1987 Sep. 7); D. H. Levy and A. Hale, IAUC, No. 4448 (1987 Sep. 15); D. H. Levy and E. A. Jacobson, IAUC, No. 4458 (1987 Sep. 29); J. B. Gibson, C. S. Morris, and A. Hale, ICQ, 9 (1987 Oct.), pp. 146, 167; B. G. Marsden, IAUC, No. 4462 (1987 Oct. 3); B. G. Marsden, MPC, No. 12309 (1987 Oct. 7); A. Hale, IAUC, No. 4479 (1987 Oct. 26); D. W. E. Green, MPC, No. 12446 (1987 Nov. 5); V. F. de Assis Neto and A. Hale, IAUC, No. 4488 (1987 Nov. 16); C. E. Spratt, D. H. Levy, R. J. Bouma, E. A. Jacobson, H. Hasegawa, A. Hale, V. F. de Assis Neto, and A. Boattini, ICQ, 10 (1988 Jan.), pp. 4, 19–20; A. F. A. L. Jones, D. A. J. Seargent, and A. R. Pearce, ICQ, 10 (1988 Apr.), p. 47; R. Haver and A. F. A. L. Jones, ICQ, 10 (1988 Jul.), p. 74; A. C. Gilmore, MPC, Nos. 13360, 13364 (1988 Aug. 27); T. Kobayashi, MPC, No. 13597 (1988 Sep. 25); M. L. Clark, ICQ, 11 (1989 Apr.), p. 31; B. G. Marsden, AJ, 99 (1990 Jun.), p. 1972; A. Ishikawa, ICQ, 12 (1990 Oct.), p. 124; B. TodorovicJuchniewicz, MPC, 17939 (1991 Mar. 30); B. Todorovic-Juchniewicz, AJ, 104 (1992 Jul.), pp. 395–6; K. T. Cernis, ICQ, 26 (2004 Apr.), p. 85; A. C. Gilmore, P. M. Kilmartin correspondence with G. W. Kronk (2011). 90P/1987 Q2 Recovered: 1987 August 29.43 (Δ = 2.82 AU, r = 2.99 AU, Elong. = 90
) (Gehrels 1) Last seen: 1988 March 13.20 (Δ = 3.40 AU, r = 3.35 AU, Elong. = 79
) Closest to the Earth: 1987 November 22 (2.1106 AU) 1987 XVI=1987v Calculated path: TAU (Rec), PER (Oct. 15) S. Nakano (1985, 1986) determined an orbit for this comet’s discovery apparition using positions obtained between 1972 October 11 and 309

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1973 September 23. He included full planetary perturbations. Nakano then integrated the comet’s motion to this apparition and predicted the comet would arrive at perihelion on 1987 August 14.81. J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) recovered this comet on two CCD images acquired during 1987 August 29.43–29.49 with the 91-cm reflector. The position on the first image was α = 4h 12.1m, δ = +26
450 (2000). Scotti confirmed the recovery on August 31.43 and August 31.48, at which time he gave the magnitude as 17.1. He also noted a moderately condensed coma and said a tail extended 8200 toward PA 262
. Scotti acquired three images on September 20, but did not provide physical descriptions. On October 16, Scotti and his colleague, T. Gehrels, acquired three more images and gave the magnitude as 17.1. He added that the coma was moderately condensed, while a tail extended 8400 toward PA 256
. D. H. Levy (Catalina Station, Mt. Bigelow, Arizona, USA) visually observed the comet on October 26, using the 154-cm reflector, and estimated the magnitude as 15.0. Images by Scotti and Gehrels were acquired on November 16. The magnitude was given as 16.7, while the nuclear magnitude was 19.3. The coma was moderately condensed. On November 29, the comet reached a maximum elongation of 169
and attained its most northerly declination of +33
. Observers at Steward Observatory made the only observations of this comet during 1988. Scotti acquired three images on January 15, giving the magnitude as 17.2 and the nuclear magnitude as 19.8. The tail extended 1.20 toward PA 242
. Three more images were acquired on February 12, at which time the magnitude was given as 17.6 and the nuclear magnitude was given as 20.7. After having moved southward since last November, the comet attained a declination of +31
on February 21 and began a northward motion. The comet was last detected during March 13.17–13.20, when Gehrels and Scotti acquired two CCD images using the 91-cm reflector. The magnitude was given as 18.1 and the nuclear magnitude was given as 21.1. The position on the final image was α = 4h 34.1m, δ = +31
140 (2000). B. G. Marsden (1987) calculated the first multiple apparition orbit. He used 23 positions from 1972 October 11 to 1987 August 31 and applied perturbations by all nine planets. The result was a perihelion date of 1987 August 10.24 and a period of 15.06 years. Additional multiple apparition orbits were calculated by D. W. E. Green (1992), Nakano (2001), K. Kinoshita (2003, 2004), and P. Rocher (2003, 2004). Green, Nakano, Kinoshita (2003), and Rocher (2003) only included full planetary perturbations in their calculations, determining the perihelion date as August 10.19–10.24 and the period as 15.06 years. Rocher (2004) and Kinoshita (2004) included the effects of nongravitational forces. They determined the perihelion date as August 10.24–10.25 and the period as 15.06 years. The nongravitational terms were given as A1 = +34.05 and A2 = 2.1356 by Rocher and A1 = +27.85 and A2 = 2.1779 by Kinoshita. The orbit of Kinoshita (2004) is given below. 310

cometography: a catalog of comets T ω Ω (2000.0) i q e 1987 Aug. 10.2546 (TT) 28.5000 13.5513 9.6189 2.988559 0.510012

absolute magnitude: H10 = 8.5, from single visual observation, H0 = 5.4, n = 7.7, from non-visual observations (Meyer) full moon: 1987 Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2, Mar. 3, Apr. 2 sources: S. Nakano, Nakano Note, No. 490 (1985 Dec. 22); S. Nakano, MPC, No. 10521 (1986 Mar. 26); S. Nakano, HBAA for 1987 (1986 Oct.), p. 79; J. V. Scotti and B. G. Marsden, IAUC, No. 4444 (1987 Sep. 1); J. V. Scotti and B. G. Marsden, MPC, Nos. 12170, 12201 (1987 Sep. 7); J. V. Scotti, ICQ, 9 (1987 Oct.), p. 169; J. V. Scotti, MPC, No. 12257 (1987 Oct. 7); J. V. Scotti, MPC, Nos. 12498, 12500 (1987 Dec. 5); T. Gehrels, J. V. Scotti, and D. H. Levy, ICQ, 10 (1988 Jan.), p. 31; J. V. Scotti, MPC, No. 12631 (1988 Jan. 4); J. V. Scotti, MPC, Nos. 12861, 12865 (1988 Apr. 2); D. W. E. Green, CCO, 7th ed. (1992), pp. 32, 67; S. Nakano, Nakano Note, No. 830 (2001 Dec. 22); K. Kinoshita correspondence with G. W. Kronk (2003, 2004); P. Rocher correspondence with G. W. Kronk (2003, 2004). 151P/1987 Q3 Discovered: 1987 August 24.43 (Δ = 1.81 AU, r = 2.57 AU, Elong. = 130
) (Helin) Last seen: 1988 February 13.14 (Δ = 3.18 AU, r = 2.96 AU, Elong. = 68
) Closest to the Earth: 1987 October 4 (1.6158 AU) 1987 Calculated path: PSC (Disc), CET (Sep. 23), PSC (Dec. 29) XVII=1987w During the second week of September 1987, E. F. Helin (Palomar Observatory, California, USA) reported the discovery of this comet on plates exposed with the 122-cm Schmidt telescope by J. E. Mueller for the Second Palomar Sky Survey. The comet first appeared on a plate exposed on 1987 August 24.43, at a position of α = 1h 24.7m, δ = +4
180 (2000). She estimated the magnitude as 16.5, and described it as condensed, with a faint diffuseness toward PA 235
. Helin confirmed the discovery when an image was also found on a plate exposed on August 26.42. An independent confirmation was made by A. J. Maury (Palomar Observatory), when he found the comet on exposures obtained by Mueller and J. Phinney with the 122-cm Schmidt telescope on September 17.36 and September 18.39. During the remainder of the comet’s apparition, observations were only made at Lowell Observatory’s Anderson Mesa Station (Arizona, USA) and Steward Observatory (Arizona, USA). Astronomers at Lowell Observatory’s Anderson Mesa Station acquired three CCD images on September 22, using the 183-cm reflector, but provided no physical descriptions. T. Gehrels and J. V. Scotti (Steward Observatory) acquired four CCD images of the comet using the 91-cm reflector on September 27. They gave the magnitude as 17.5 and reported a faint tail extending 2500 toward PA 257
. The comet reached a maximum elongation of 174
on October 11. 311

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Gehrels and Scotti acquired two images on October 16, when the magnitude was given as 17.7. Astronomers at Lowell Observatory’s Anderson Mesa Station acquired two images on October 26, but again provided no physical description. The comet attained its most southerly declination of 0
on November 12. The final images of the year were acquired by Scotti. A single image on December 21 revealed a nuclear magnitude of 21.4, while a pair of images on December 22 revealed a magnitude of 18.8. The first observations of 1988 were obtained on January 15, when Scotti acquired two images and noted a magnitude of 19.9. Astronomers at Lowell Observatory’s Anderson Mesa Station acquired two images a little later that same night, but provided no physical description. Scotti acquired two more images on January 21 and gave the magnitude as 19.8. He described the comet as diffuse and uncondensed. The final observations of this comet were made on 1988 February 12.11, February 12.13, and February 13.14, when Gehrels and Scotti acquired CCD images using the 91-cm reflector. The magnitude was given as 19.8 and the image was described as faint and diffuse. The comet’s position on the final image was α = 2h 05.7m, δ = +8
070 (2000). The first orbit was calculated by B. G. Marsden and was published on 1987 September 19. He used eight positions from 1987 August 24 to September 18 and determined a short-period orbit with a perihelion date of 1987 August 16.49 and a period of 14.20 years. Marsden and D. W. E. Green calculated additional orbits during the next few months as observers continued to follow the comet. These established the perihelion date as August 12 and the period as 14.5 years. The first orbit to use positions spanning the entire apparition was published by Green on 1988 August 27. Green used 29 positions and perturbations by all nine planets, determining the perihelion date as August 12.14 and the period as 14.45 years. Further orbits calculated from positions spanning the entire apparition were published by P. Rocher (1995), K. Kinoshita (1998), S. Nakano (1998), and Marsden (1999). The perihelion date was given as August 12.14–12.20 and the period was 14.45–14.46 years. Multiple apparition orbits have been calculated by Marsden (2001), Kinoshita (2001, 2003), Rocher (2002), and Nakano (2012). These used positions from the 1987 and 2001 apparitions and full planetary perturbations. In general, they determined the perihelion date as August 12.20 and the period as 14.45 years. The orbit of Nakano (2012) is given below. T ω Ω (2000.0) i q e 1987 Aug. 12.2013 (TT) 216.2767 143.7338 4.6867 2.571361 0.566515

absolute magnitude: H10 = 10.3, from single visual observation, H0 = 5, n = 10.7, from non-visual observations (Meyer) full moon: 1987 Aug. 9, Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2, Mar. 3 312

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sources: E. F. Helin and J. E. Mueller, IAUC, No. 4448 (1987 Sep. 15); A. J. Maury, J. E. Mueller, J. Phinney, and B. G. Marsden, IAUC, No. 4449 (1987 Sep. 19); E. F. Helin, J. E. Mueller, A. J. Maury, J. Phinney, T. Gehrels, J. V. Scotti, and B. G. Marsden, MPC, Nos. 12257, 12309 (1987 Oct. 7); T. Gehrels, J. V. Scotti, and B. G. Marsden, MPC, Nos. 12363, 12440 (1987 Nov. 5); [Anderson Mesa], J. V. Scotti, and D. W. E. Green, MPC, Nos. 12749, 12792 (1988 Feb. 2); J. V. Scotti, MPC, Nos. 12861–2, 12865 (1988 Apr. 2); T. Gehrels and J. V. Scotti, MPC, Nos. 13006–7 (1988 May 1); D. W. E. Green, MPC, No. 13459 (1988 Aug. 27); P. Rocher correspondence with G. W. Kronk (1995, 2002); K. Kinoshita correspondence with G. W. Kronk (1998, 2001, 2003); S. Nakano, Nakano Note, No. 684 (1998 May 2); B. G. Marsden, CCO, 13th ed. (1999), pp. 36–7; B. G. Marsden, CCO, 14th ed. (2001), pp. 98–9; S. Nakano, Nakano Note, No. 2228 (2012 Apr. 16). 76P/West– Recovered: 1987 September 27.48 (Δ = 2.26 AU, r = 1.69 AU, Elong. = 44
) Kohoutek– Last seen: 1988 April 12.38 (Δ = 2.01 AU, r = 2.78 AU, Elong. = 132
) Ikemura Closest to the Earth: 1988 February 25 (1.8095 AU) Calculated path: LEO (Rec), LMi (Oct. 11), LEO (Oct. 22), COM (Nov. 11), 1987 XV=1987x BOO (Dec. 31), CVn (1988 Jan. 15), BOO (Jan. 24), CVn (Jan. 29), BOO (Jan. 31), CVn (Mar. 2) Predictions for the return of this comet were published by S. Nakano (1986) and S. W. Milbourn (1986). They both used positions from the 1974 and 1981 apparitions, as well as full planetary perturbations. Nakano determined the upcoming perihelion date as 1987 July 27.39, while Milbourn determined it as July 27.40. These indicated the comet passed 0.58 AU from Jupiter on 1983 November 18, increasing the perihelion distance from 1.40 AU to 1.57 AU and increasing the period from 6.12 years to 6.40 years. J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) recovered this comet on CCD images acquired on 1987 September 27.48 and September 27.50, using the 91-cm reflector. He estimated the magnitude as 17 and noted a tail extending 6900 in PA 291
. The position on the first date was α = 9h 55.0m, δ = +26
390 (2000). T. Seki (Geisei, Kochi, Japan) independently recovered this comet on October 1.82, when he found it on a photograph obtained using the 60-cm reflector. The magnitude was estimated as 18. The comet moved southward following its recovery and attained a declination of +25
on November 28 before turning northward. Scotti acquired two images of the comet on December 21, which revealed a magnitude of 18.4 and a nuclear magnitude of 21.0. There was also a tail extending 2.250 toward PA 323
. Scotti obtained three more images on 1988 January 15 and another two on January 21. He gave the nuclear magnitude as 21.5 on the first date and the magnitude as 18.3 on the last. Also on the last date, Scotti noted a tail extending 4000 toward PA 295
. The comet’s elongation increased to a maximum of 135
on March 29 and then the comet attained its most northerly declination of +39
on April 2. 313

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The comet was last detected on three CCD images acquired during 1988 April 12.35–12.38, by T. Gehrels and Scotti using the 91-cm reflector. They gave the nuclear magnitude as 21.3. The position on the last date was α = 13h 24.7m, δ = +38
450 (2000). Multiple apparition orbits have been calculated by T. Kobayashi (1987), G. Forti (1989), Nakano (1990, 1994, 1997, 2006, 2010), B. G. Marsden (1997), and K. Kinoshita (1998, 2009). All of these used full planetary perturbations, while all except Marsden also solved for nongravitational effects. They determined the perihelion date as July 27.27 and the period as 6.40 years. The nongravitational terms have shown large variations and no one set can represent the observations at every observed apparition. They were greatest during the first three apparitions (1975–1987), probably as a result of the comet’s very close approach to Jupiter on 1972 March 23 (0.012 AU), with Kobayashi, Forti, and Nakano (1990) giving terms within the following ranges: A1 = +0.21 to +0.43 and A2 = 0.1277 to 0.1218. Adding the observations from the 1993 apparition to those of the previous three apparitions enabled Nakano (1994, 1997) and Kinoshita (1998) to determine smaller terms within the following ranges: A1 = 0.05 to 0.04 and A2 = 0.1002 to 0.0957. Using these same four apparitions, Marsden found acceptable residuals without the need to solve for nongravitational effects. Using apparitions spanning the period of 1987 to 2006, Nakano (2006) and Kinoshita (2009) determined terms within the following ranges: A1 = 0.18 to +0.15 and A2 = 0.0368 to 0.0360. Nakano (2010) used positions spanning the apparitions of 1981–2006 and determined the nongravitational terms as A1 = 0.15 and A2 = 0.0371. The orbit of Nakano (2010) is given below. T ω Ω (2000.0) i q e 1987 Jul. 27.2628 (TT) 359.8427 84.2130 30.5776 1.570587 0.544405

absolute magnitude: H0 = 13.3, n = 4.2 (Meyer) full moon: 1987 Sep. 7, Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2, Mar. 3, Apr. 2, May 1 sources: S. Nakano, MPC, No. 10520 (1986 Mar. 26); S. W. Milbourn, HBAA for 1987 (1986 Oct.), pp. 78–9; J. V. Scotti, IAUC, No. 4456 (1987 Sep. 28); T. Seki, IAUC, No. 4464 (1987 Oct. 4); J. V. Scotti, MPC, No. 12257 (1987 Oct. 7); T. Seki and T. Kobayashi, MPC, Nos. 12363, 12454 (1987 Nov. 5); J. V. Scotti, MPC, Nos. 12749, 12751 (1988 Feb. 2); J. V. Scotti, MPC, No. 12862 (1988 Apr. 2); T. Gehrels and J. V. Scotti, MPC, No. 13006 (1988 May 1); G. Forti, AAP, 215 (1989), pp. 383, 385; S. Nakano, Nakano Note, No. 542 (1990 May 3); S. Nakano, CCO, 9th ed. (1994), pp. 34, 70, 76; B. G. Marsden, CCO, 12th ed. (1997), pp. 68–9; S. Nakano, Nakano Note, No. 654 (1997 May 3); K. Kinoshita correspondence with G. W. Kronk (1998, 2009); S. Nakano, Nakano Note, No. 1358 (2006 Sep. 22); S. Nakano, Nakano Note, No. 1903 (2010 Apr. 6). 314

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C/1987 T1 (Levy) Discovered: 1987 October 11.13 (Δ = 1.54 AU, r = 0.89 AU, Elong. = 33
) Last seen: 1987 November 21.73 (Δ = 2.19 AU, r = 1.58 AU, Elong. = 40
) 1987 XXI=1987y Closest to the Earth: 1987 September 24 (1.4715 AU) Calculated path: BOO (Disc), SER (Oct. 17), HER (Oct. 28), OPH (Nov. 7) When it came to comet hunting, D. H. Levy (Tucson, Arizona, USA) had been concerned about objects close to the horizon for some time. So, he took a step toward alleviating the problem – he had a platform built on the roof of his house, which was completed on 1987 October 7. On the night of October 10/11, Levy was sweeping for comets from the platform with his 20-cm reflector, when he spotted a comet near the horizon. He observed the comet for only a brief time, but suspected eastward motion. The comet would not have been seen had Levy not been observing from the platform. The date of the observation was given as October 11.13 and the position was α = 14.6h, δ = +17
(2000). Levy estimated the magnitude as 9.5, and described the comet as diffuse, with a condensation, but with no tail. The diameter was given as 30 . Several confirmations were made within the next 24 hours. The first was obtained on October 11.99, when R. Meier (Ottawa, Ontario, Canada) determined the magnitude as 9.6 using a 15-cm refractor. T. Dickinson (Yarker, Ontario, Canada) then spotted the comet with his 14-cm refractor on October 12.00. He estimated the magnitude as 9.5. Levy obtained his own confirmation on October 12.08, when he determined the magnitude as 9.3 and the coma diameter as 30 . He described the coma as “asymmetric, slightly elongated and diffuse with some condensation.” In a newspaper interview published in the Reno Gazette-Journal, Levy described the comet “as a very delicate, bluish, fuzzy patch.” J. V. Scotti independently confirmed the comet on October 12.09, while observing with Levy and estimated the magnitude as 9. The comet faded during the remainder of October as it moved away from both the Earth and Sun. J. D. Shanklin (Cambridge Observatory, England) saw the comet on five nights between the 13th and 24th, using a 33-cm reflector. He noted a substantial decrease in brightness from magnitude 8.9 to 11.2. R. J. Bouma (Groningen, Netherlands) observed the comet on four nights between the 19th and 29th, using a 25-cm reflector. He stated that the brightness faded from magnitude 9.4 to 10.5. J. E. Bortle (Stormville, New York, USA) used a 32-cm reflector on the 22nd and 25th, reporting a magnitude of 9.8 on both nights. Most observers reported an average coma diameter of 30 during the month and noted that the coma became almost completely uncondensed by month’s end. G. R. Chester (Rixeyville, Virginia, USA) photographed the comet on the 16th, using a 14-cm reflector. He said it revealed a tail extending 50 in PA 355
. The comet continued to fade during November and reached a maximum elongation of 41
on the 9th. On this same date, R. A. Keen (Mt. Thorodin, 315

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Colorado, USA) determined the magnitude as 11.0, using a 32-cm reflector. He noted a very slightly condensed coma that was 40 across. A. Hale (Las Cruces, New Mexico, USA) was not able to detect the comet on the 11th, using a 41-cm reflector, and suggested it was fainter than magnitude 13.0. Morris and Levy observed the comet using a 26-cm reflector on the 12th and said the magnitude was about 12.5 and 12.6, respectively. Morris said the coma was very slightly condensed and 1.50 in diameter. The final astrometric observations were obtained during November 17.07–17.08 and November 19.07, when Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired CCD images using the 91-cm reflector. On the first night, he described the comet as “diffuse and uncondensed” with a tail extending 20 in PA 343
. On the second night, he estimated the magnitude as 17. The position on the final image was α = 17h 33.9m, δ = +9
130 (2000). Two visual observations were reported after Scotti’s images were obtained. Levy (Catalina Station, Mt. Bigelow, Arizona, USA) spotted the comet using the 154-cm reflector on November 20.08. He estimated the magnitude as 13.0 and noted an uncondensed coma 30 across. A. Boattini (Piazzano, Italy) saw the comet using his 33-cm reflector on November 21.73. He determined the magnitude as 12.9. The first orbit calculated for this comet was parabolic and was published on October 17. D. W. E. Green used four positions from October 13–17 and determined the perihelion date as 1987 September 9.16. Green published a revision on November 5. This used nine positions from October 13–21 and also gave the perihelion date as September 9.16. The final orbit was calculated by B. G. Marsden and was published on December 5. This used 13 positions from October 13 to November 17 and gave the perihelion date as September 9.17. This orbit is given below. T 1987 Sep. 9.1716 (TT)

ω 13.1872

Ω (2000.0) 143.7254

i 62.5345

q 0.515185

e 1.0

absolute magnitude: H0 = 8.6, n = 5 (Meyer) full moon: 1987 Oct. 7, Nov. 5, Dec. 5 sources: D. H. Levy, T. Dickinson, J. V. Scotti, and R. Meier, IAUC, No. 4468 (1987 Oct. 12); D. H. Levy, Reno Gazette-Journal (1987 Oct. 15), p. 4D, col. 1; D. W. E. Green, A. Hale, D. H. Levy, and G. R. Chester, IAUC, No. 4471 (1987 Oct. 17); D. W. E. Green, IAUC, No. 4476 (1987 Oct. 24); D. H. Levy, ICQ, 9 (1987 Oct.), p. 167; D. W. E. Green, MPC, No. 12445 (1987 Nov. 5); J. V. Scotti and B. G. Marsden, MPC, Nos. 12499–500, 12575 (1987 Dec. 5); J. V. Scotti, MPC, No. 12631 (1988 Jan. 4); R. J. Bouma, J. E. Bortle, A. Hale, C. S. Morris, D. H. Levy, J. V. Scotti, and A. Boattini, ICQ, 10 (1988 Jan.), pp. 20–1; D. H. Levy and R. A. Keen, ICQ, 10 (1988 Apr.), pp. 37, 47; J. D. Shanklin, ICQ, 15 (1993 Oct.), p. 156; D. H. Levy correspondence with M. Meyer (2014 May 27). 316

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C/1987 T2 Discovered: 1987 October 5.91 (Δ = 0.98 AU, r = 0.03 AU, Elong. = 1.1
) (SMM 1) Last seen: 1987 October 5.97 (Δ = 0.98 AU, r = 0.02 AU, Elong. = 0.6
) Closest to the Earth: 1987 October 4 (0.9589 AU) 1987 XXII Calculated path: VIR (Disc) [Did not leave this constellation] S. A. Beck (High Altitude Observatory, Boulder, Colorado, USA) discovered this comet during a routine inspection of coronagraph/polarimeter images obtained by the Solar Maximum Mission (SMM). The first image was from 1987 October 5.91 and the comet was about magnitude 0. The position was given as α = 12h 41.2m, δ = 5
130 (2000). The only other image was obtained on October 5.97, when the position was given as α = 12h 43.5m, δ = 5
070 (2000). The comet was not detected leaving the Sun’s vicinity. B. G. Marsden (1987) used the positions from October 5 and said a Kreutz-type orbit with a perihelion date of 1987 October 6.07 fit the positions with residuals of no more than 0.80 . A very similar orbit was later published by Marsden (1989) and this is given below. T 1987 Oct. 6.069 (TT)

ω 80.591

Ω (2000.0) 1.159

i 144.256

q 0.00538

e 1.0

sources: S. A. Beck and B. G. Marsden, IAUC, No. 4621 (1988 Jul. 1); B. G. Marsden, AJ, 98 (1989 Dec.), pp. 2308, 2309. 128P/1987 U1 Prediscovery: 1987 September 24.38 (Δ = 2.38 AU, r = 3.32 AU, Elong. = 157
) (Shoemaker– Discovered: 1987 October 18.34 (Δ = 2.28 AU, r = 3.28 AU, Elong. = 175
) Holt 1) Last seen: 1989 February 6.56 (Δ = 2.48 AU, r = 3.37 AU, Elong. = 150
) Closest to the Earth: 1987 October 19 (2.2818 AU) 1988 VII=1987z Calculated path: PSC (Pre), ARI (1988 Feb. 18), TAU (Apr. 24), ORI (Jul. 21), GEM (Aug. 9) In the course of the Palomar Asteroid and Comet Survey, C. S. Shoemaker, E. M. Shoemaker, and H. E. Holt (Palomar Observatory, California, USA) discovered this comet on films exposed on 1987 October 18.34 and October 19.48 with the 46-cm Schmidt telescope. They initially estimated the magnitude as 14.5, but later revised it to 15, and described the comet as strongly condensed, with a small, slightly asymmetric coma extending southwestward. The position on the first image was α = 1h 10.7m, δ = +9
040 (2000). The comet was discovered near its maximum elongation, which was 178
on October 14. Two prediscovery observations were reported. Shortly after the comet was discovered, images were found on films exposed by the Shoemakers during September 24.38–24.42. No physical descriptions were provided. The position on the first film was α = 1h 24.3m, δ = +10
520 (2000). One year after discovery, N. S. Chernykh (Crimean Astrophysical ObservatoryNauchnyj, Ukraine) reported a position obtained from a photograph 317

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exposed on October 2.96, using the 40-cm Zeiss double astrograph. The magnitude was given as 16. Confirmation and follow-up observations were reported during the remainder of October. T. Seki (Geisei, Kochi, Japan) photographed the comet on the 21st, using a 60-cm reflector, and estimated a magnitude of 17. On the 22nd and 23rd, C.-Y. Shao and R. E. McCrosky (Oak Ridge Observatory, Massachusetts, USA) obtained photographic exposures of 12–15 minutes with the 155-cm reflector. They described the comet as a nearly stellar image. Also on the 23rd, S. Ueda (Kushiro, Hokkaido, Japan) photographed the comet with a 16-cm reflector and estimated the magnitude as 15. T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired CCD images on the 26th, using the 91-cm reflector. They noted a 3800 tail extending toward PA 254
and said that the comet appeared almost starlike. Seki photographed the comet again on the 27th and 28th, and gave the magnitude as 17.5 and 18, respectively. Only a few descriptions of the comet were provided during the remainder of 1987. Scotti acquired CCD images on November 16 and said the comet appeared almost starlike, with a nuclear magnitude of 18.7. He said the coma was 0.550 across, while a tail extended 3000 in PA 60
. On the 11th, 12th, and 13th, A. Hale (Las Cruces, New Mexico, USA) attempted to visually detect the comet using his 41-cm reflector. He did not succeed and concluded that it must have been fainter than magnitude 13.5 on the first date and 14.0 on the two latter dates. D. H. Levy (Catalina Station, Mt. Bigelow, Arizona, USA) visually observed the comet using the 154-cm reflector on the 19th and estimated the magnitude as 13.5. Seki estimated the magnitude as 17 on the 20th. On November 22 and 24, T. Kojima (Chiyoda, Gunma, Japan) photographed the comet using a 25-cm reflector and estimated the magnitude as 16 on both dates. The comet attained its most southerly declination of +6
on December 10. Only a few observations were obtained during the early weeks of 1988, as the comet’s elongation from the Sun decreased. Hale again tried to visually observe the comet on January 9, but was unsuccessful. He concluded that it must have been fainter than magnitude 13.5. T. Nakamura and M. Hamabe (Kiso Observatory, Nagano, Japan) photographed the comet on the 20th using the 105-cm Schmidt telescope. They estimated the magnitude as 15 and noted a tail extending 500 in PA 70
. Scotti acquired CCD images on January 21 and McCrosky photographed the comet on January 22, but neither astronomer provided a description. The final observations made prior to the comet becoming lost in the Sun’s glare were made by the Shoemaker’s and Holt on February 18 and 19; however, no descriptions were provided. The comet passed only 2
from the Sun on May 26. After having moved northward since last December, the comet attained a declination of +21
on July 17. Hale attempted to visually observe the comet with his 41-cm reflector on September 16, October 19, and November 13. He was unsuccessful on all 318

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three dates, judging it to be fainter than magnitude 13.5 on the first date and 14.0 on the latter two. No professional observatory observed this comet during the remainder of this apparition; however, several diligent Japanese amateur astronomers continued to acquire images and, therefore, precise positions. During December, Kojima photographed the comet on the 7th and 17th, estimating the magnitude as 16 on both nights. T. Hioki (Okutama, Tokyo Metropolis, Japan) photographed the comet using a 30-cm reflector on the 11th, but provided no description. On December 18, Seki estimated the photographic magnitude as 18. After having moved southward since midJuly, the comet attained a declination of +15
on December 17 and then began a northward motion. Only a few observations were made during the first weeks of 1989. Kojima photographed the comet on January 6 and 28, and estimated the magnitude as 16 on both nights. The comet reached a maximum elongation of 174
on January 12. Another photograph by Kojima on February 1 revealed a magnitude of 16.5. On February 2, T. Niijima and K. Kanai (Ojima, Gunma, Japan) imaged the comet using a 30-cm reflector and gave a magnitude of 17. The comet was last detected during February 6.53 and February 6.56, when Kojima obtained photographs using the 25-cm reflector. He estimated the magnitude as 16.5. The comet’s position on the final photograph was α = 7h 16.7m, δ = +16
200 (2000). The first orbit was calculated by D. W. E. Green and was published on 1987 October 26. Green used seven positions obtained during October 18–23. The result was an elliptical orbit with a perihelion date of 1988 March 23.14 and a period of 9.04 years. Green published a revised orbit on November 5. This used 15 positions from September 24 to October 26. The perihelion date was given as May 12.98, while the period was 9.57 years. During the next few months, new orbits calculated by Green and B. G. Marsden narrowed the perihelion date to May 21.42 and the period to 9.56 years. The first orbit to use positions spanning the entire period of visibility was calculated by S. Nakano (1989). He took 65 positions and included full planetary perturbations. The result was a perihelion date of May 21.36 and a period of 9.55 years. Multiple apparition orbits have been calculated by Nakano (1997, 2004, 2006, 2014), K. Kinoshita (1999, 2007), and P. Rocher (1999, 2006, 2009). All of these calculations included full planetary perturbations, while those published from 2006 onward also solved for nongravitational effects. The result was a perihelion date of May 21.35–21.41 and a period of 9.55–9.56 years. Kinoshita and Rocher determined nongravitational effects of type II. These terms were given as A1 = 7.86 and A2 = 0.8635 by Rocher (2006), A1 = +1.77 and A2 = 0.9411 by Kinoshita (2007), and A1 20.63 and A2 = 0.8087 by Rocher (2009). These show a large variation in the radial term, while the transverse term is fairly consistent, not an uncommon occurrence when calculating nongravitational effects for comets with large perihelion distances. 319

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Nakano approached the nongravitational effects in a different fashion, using S. Yabushita’s theory of sublimating carbon monoxide (or molecular nitrogen). He gave terms of Y1 = 0.66 and Y2 = 0.0024 in 2006 and Y1 = 0.39 and Y2 = 0.0049 in 2014. The orbit of Nakano (2014) is given below. T ω Ω (2000.0) i q e 1988 May 21.3565 (TT) 210.3588 214.5790 4.3625 3.052976 0.321858

absolute magnitude: H10 = 6.5, from single visual observation, H10 = 8.8, from non-visual observations (Meyer) full moon: 1987 Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2, Mar. 3, Apr. 2, May 1, May 31, Jun. 29, Jul. 29, Aug. 27, Sep. 25, Oct. 25, Nov. 23, Dec. 23, 1989 Jan. 21, Feb. 20 sources: C.-Y. Shao and R. E. McCrosky, HOPL (1987, 1988); C. S. Shoemaker, E. M. Shoemaker, and H. E. Holt, IAUC, No. 4472 (1987 Oct. 19); C. S. Shoemaker, E. M. Shoemaker, H. E. Holt, C.-Y. Shao, R. E. McCrosky, and D. W. E. Green, IAUC, No. 4479 (1987 Oct. 26); C. S. Shoemaker, E. M. Shoemaker, H. E. Holt, T. Gehrels, J. V. Scotti, T. Seki, and D. W. E. Green, MPC, Nos. 12364–5, 12446 (1987 Nov. 5); B. G. Marsden, IAUC, No. 4508 (1987 Dec. 5); T. Seki, S. Ueda, and B. G. Marsden, MPC, Nos. 12499, 12576 (1987 Dec. 5); J. V. Scotti, A. Hale, and D. H. Levy, ICQ, 10 (1988 Jan.), p. 32; J. V. Scotti and T. Kojima, MPC, Nos. 12631–2 (1988 Jan. 4); C.-Y. Shao, R. E. McCrosky, J. V. Scotti, and D. W. E. Green, MPC, Nos. 12749, 12792 (1988 Feb. 2); T. Nakamura, M. Hamabe, C.-Y. Shao, R. E. McCrosky, J. V. Scotti, and [Palomar], MPC, Nos. 12862, 12865 (1988 Apr. 2); D. W. E. Green, MPC, No. 13460 (1988 Aug. 27); A. Hale, ICQ, 10 (1988 Oct.), p. 122; N. S. Chernykh, MPC, No. 13638 (1988 Oct. 25); A. Hale, ICQ, 10 (1989 Jan.), p. 25; T. Kojima and T. Hioki, MPC, No. 14083 (1989 Feb. 20); T. Seki, T. Kojima, T. Niijima, and K. Kanai, MPC, No. 14232 (1989 Mar. 22); P. Wild, MPC, No. 14387 (1989 Apr. 21); S. Nakano, MPC, No. 14592 (1989 May 20); N. S. Chernykh and L.-I. Chernykh, Asteroids, comets, meteors III; Proceedings of the International Meeting, Uppsala, Sweden, June 12-16, 1989. Uppsala, Sweden (1990), pp. 33–6; S. Nakano, CCO, 12th ed. (1997), pp. 76–7; K. Kinoshita correspondence with G. W. Kronk (1999, 2007); P. Rocher correspondence with G. W. Kronk (1999, 2006, 2009); S. Nakano, Nakano Note, No. 1049 (2004 Apr. 7); S. Nakano, Nakano Note, No. 1367 (2006 Sep. 30); B. A. Skiff correspondence with G. W. Kronk (2011); S. Nakano, Nakano Note, No. 2702 (2014 Jun. 9). 120P/1987 U2 Discovered: 1987 October 18.27 (Δ = 1.77 AU, r = 2.76 AU, (Mueller 1) Elong. = 175
) Last seen: 1988 February 13.17 (Δ = 2.98 AU, r = 2.78 AU, Elong. = 69
) 1987 Closest to the Earth: 1987 October 17 (1.7670 AU) XXXI=1987a1 Calculated path: PSC (Disc), ARI (1988 Feb. 8) 320

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J. E. Mueller (Palomar Observatory, California, USA) discovered this comet in the course of the Second Palomar Sky Survey. The comet was first noticed on a plate exposed with the 122-cm Schmidt telescope on 1987 October 18.27, and the position was given as α = 1h 15.4m, δ = +12
420 (2000). She estimated the magnitude as 17, and described the comet as diffuse, with condensation, and with an apparent tail extending 20–3000 toward the southsouthwest. A confirmation plate was exposed with the same telescope by N. Reid and Mueller on October 19.30. They estimated the magnitude as 17. Near the end of October, E. M. Shoemaker, C. S. Shoemaker, and H. E. Holt (Palomar) found the comet near the edge of film exposed for the Palomar Asteroid and Comet Survey. The exposure dates were October 18.34 and October 19.48 and they had used the 46-cm Schmidt telescope. Several astronomers were able to follow the comet during the remainder of October. The Shoemakers and Holt exposed additional film using the 46-cm Schmidt telescope on the 20th and 21st, giving the magnitude as 17.5 on the first night. T. Seki (Geisei, Kochi, Japan) obtained two photographs on the 21st and estimated the magnitude as 18. C.-Y. Shao (Oak Ridge Observatory, Massachusetts, USA) used the 155-cm reflector to obtain photographic exposures of nine minutes on the 22nd and 46 minutes on the 24th. No descriptive information was provided. R. E. McCrosky (Oak Ridge Observatory) obtained a 45-minute exposure using the 155-cm exposure on the 23rd and described the comet as diffuse, with no apparent condensation. T. Gehrels and J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired several CCD images of the comet on the 26th and 27th. For the last date, they gave the magnitude as 17.1, noting a moderately condensed coma and a tail extending 6000 in PA 233
. Seki obtained another photograph on the 27th and estimated the magnitude as 18.5. A. Maury and Mueller acquired images of the comet on the 28th, but provided no physical description. A. Hale (Las Cruces, New Mexico, USA) tried to visually spot the comet on the 20th, using his 41-cm reflector; however, nothing was seen and he suggested the comet was probably fainter than magnitude 13.5. The comet was seen by only three observers during November: Gehrels, Scotti, and D. H. Levy (Catalina Station, Mt. Bigelow, Arizona, USA). The CCD observations of Gehrels and Scotti were made using the 91-cm reflector. On the 16th, they noted a magnitude of 17, a nuclear magnitude of 20.2, and a tail extending 6900 in PA 225
. On the 24th, they noted a nuclear magnitude of 19.9, a moderately condensed coma 3100 in diameter, and a tail extending 7600 in PA 231
. Levy visually observed the comet on the 20th using the 154-cm reflector. Using a power of 654, he estimated the magnitude as 14.5. After having moved southward since its recovery, the comet attained a declination of +12
on November 19 and then began a northward motion. The comet was observed on only two nights during December, with the observations being made by Gehrels and Scotti. On the 21st, they gave the 321

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magnitude as 17.8 and the nuclear magnitude as 21.1. In addition, they noted a coma 3500 across. On the 23rd, they gave the magnitude as 17.9 and the nuclear magnitude as 21.1. The tail extended 2900 in PA 237
. The final observations of this comet were acquired by Scotti during early 1988. Using the 91-cm reflector, he acquired multiple CCD images of the comet on January 15, February 12, and February 13. On the last two dates, Scotti gave the magnitude as 18.7 and 18.4, respectively. The last observation was acquired on February 13.17, when the position was α = 1h 53.5m, δ = +18
080 (2000). The first orbit was calculated by D. W. E. Green and was published on 1987 October 27. Green used six positions obtained during October 18–24 to obtain a short-period orbit with a perihelion date of 1987 October 18.32 and a period of 8.21 years. The orbit was refined during the next few months. Green determined the perihelion date as 1987 December 4.88 and the period as 8.31 years on November 5. B. G. Marsden gave the perihelion date as December 6.18 and the period as 8.46 years on 1988 January 4. On February 2, Green determined the perihelion date as December 5.08 and the period as 8.45 years. Orbits covering the entire period of visibility were published by Green on 1988 August 27 and S. Nakano (1993). Using 28 positions, Green determined the perihelion date as December 4.14 and the period as 8.45 years. Nakano used 29 positions and determined the perihelion date as December 4.18 and the period as 8.45 years. Multiple apparition orbits have been calculated by Marsden (1996), K. Kinoshita (1998, 2004, 2007), and Nakano (2001, 2005, 2010). These calculations included full planetary perturbations. The general result was a perihelion date of December 4.09–4.10 and a period of 8.44 years. The orbit of Kinoshita (2007) is given below. T ω Ω (2000.0) i q e 1987 Dec. 4.0866 (TT) 30.2824 4.6447 8.8004 2.746609 0.337644

absolute magnitude: H10 = 8.7, from single visual observation, H10 = 11.9, from non-visual observations (Meyer) full moon: 1987 Oct. 7, Nov. 5, Dec. 5, 1988 Jan. 4, Feb. 2, Mar. 3 sources: C.-Y. Shao and R. E. McCrosky, HOPL (1987); J. E. Mueller and N. Reid, IAUC, No. 4472 (1987 Oct. 19); E. M. Shoemaker, C. S. Shoemaker, H. E. Holt, C.-Y. Shao, R. E. McCrosky, and D. W. E. Green, IAUC, No. 4480 (1987 Oct. 27); E. M. Shoemaker, C. S. Shoemaker, H. E. Holt, T. Seki, C.-Y. Shao, R. E. McCrosky, T. Gehrels, J. V. Scotti, and D. W. E. Green, MPC, Nos. 12364–5, 12446 (1987 Nov. 5); A. Maury and J. E. Mueller, MPC, No. 12499 (1987 Dec. 5); A. Hale, T. Gehrels, J. V. Scotti, and D. H. Levy, ICQ, 10 (1988 Jan.), p. 30; T. Seki, T. Gehrels, J. V. Scotti, and B. G. Marsden, MPC, Nos. 12631–2, 12709 (1988 Jan. 4); T. Gehrels, J. V. Scotti, and D. W. E. Green, MPC, Nos. 12749–51, 12792 (1988 Feb. 2); J. V. Scotti, MPC, 322

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No. 12862 (1988 Apr. 2); T. Gehrels and J. V. Scotti, MPC, No. 13006 (1988 May 1); D. W. E. Green, MPC, No. 13459 (1988 Aug. 27); S. Nakano, Nakano Note, No. 590 (1993 Apr. 7); B. G. Marsden, CCO, 11th ed. (1996), pp. 72–3; K. Kinoshita correspondence with G. W. Kronk (1998, 2004, 2007); S. Nakano, Nakano Note, No. 790 (2001 Apr. 28); S. Nakano, Nakano Note, No. 1268 (2005 Oct. 26); S. Nakano, Nakano Note, No. 1918 (2010 Apr. 23); A. Hale correspondence with G. W. Kronk (2011). C/1987 U3 Prediscovery: 1986 December 21.45 (Δ = 4.60 AU, r = 4.91 AU, Elong. = 103
) (McNaught) Discovered: 1987 October 18.42 (Δ = 1.80 AU, r = 1.29 AU, Elong. = 44
) Last seen: 1988 May 10.93 (Δ = 3.14 AU, r = 2.54 AU, Elong. = 46
) 1987 Closest to the Earth: 1988 January 30 (1.5403 AU) XXXII=1987b1 Calculated path: DOR (Pre), RET (1987 Jan. 22), DOR (Jan. 26), HOR (Feb. 2), ERI (Apr. 2), HOR (Apr. 10), CAE (May 8), COL (Jun. 11), PIC (Jul. 3), PUP (Jul. 13), CAR (Aug. 7), CEN (Sep. 20), CRU (Sep. 25), CEN (Oct. 3), LUP (Oct. 16), SCO (Nov. 13), OPH (Nov. 29), SER (Dec. 12), OPH (Dec. 18), HER (1988 Jan. 12), VUL (Jan. 22), LYR (Jan. 25), CYG (Jan. 29), LYR (Jan. 30), CYG (Jan. 31), CEP (Feb. 27), CAS (Mar. 13), CAM (Apr. 22) R. H. McNaught (Siding Spring Observatory, New South Wales, Australia) discovered this comet on photographs exposed with an 85mm camera lens on 1987 October 18.42. He gave the comet’s position as α = 14h 26.0m, δ = 52
130 (2000). He estimated the magnitude as 9 and described the comet as condensed, with a coma about 20 across. McNaught subsequently found the comet on earlier photographs exposed with the same lens on October 9.40, October 10.41, October 11.42, October 14.42, and October 17.44. He noted that the comet was about magnitude 10 on October 9. In the course of doing research for this book, M. Meyer found another prediscovery image. The comet appeared as a trail on a 90-minute exposure that was obtained in the course of the SERC-J survey during 1986 December 21.45–21.51. This survey used the 122-cm Schmidt telescope at Siding Spring Observatory. The magnitude of the brightest part of the trail was estimated as 18.5, while the position of the beginning of the trail was α = 4h 47.2m, δ = 54
420 (2000). The comet was approaching perihelion and was exclusively visible to observers in the Southern Hemisphere following discovery. A. R. Pearce (Perth, Western Australia, Australia) saw the comet on October 20, 21, 22, and 24, using a 20-cm reflector, and noted an increase in magnitude from 8.8 to 8.6. A. F. A. L. Jones (Nelson, New Zealand) used a 32-cm reflector on October 21 and 31, to estimate a magnitude of 9.3 and 8.9, respectively. M. L. Clark (Perth) gave a magnitude of 8.5 on October 21, using a 31-cm reflector. On October 27, McNaught observed with 20  120 binoculars and determined the magnitude as 8.3. On the same day, D. A. J. Seargent (The Entrance, New South Wales, Australia) used 15  80 binoculars and judged the magnitude as 8.6. Observers generally described the coma as 323

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moderately condensed and 2–2.50 across. Clark and McNaught both reported seeing a tail. Clark said it extended 240 in PA 194
on the 21st, while McNaught described it as faint and diffuse on the 27th, extending 40 in PA 190
. Only three brightness estimates were reported during November, as the comet moved deeper into evening twilight. Jones determined the magnitude as 9.0 and said the coma was slightly condensed on the 3rd. Clark saw the comet on the 8th and gave the magnitude as 7.9. He noted a moderately condensed 20 across, as well as a tail extending 180 in PA 71
. Another observation by Clark on the 12th revealed a magnitude of 7.4 and a moderately condensed coma 3.50 across. The final observation acquired prior to the comet becoming lost in the Sun’s glare came from astronomers at Perth Observatory (Bickley, Western Australia, Australia) on November 12, just minutes after Clark saw the comet. No physical description was provided. The comet reached a minimum elongation of 4
on December 5 and passed perihelion on December 11. Thereafter, it began moving into the skies of Northern Hemisphere observers. A. Nakamura (Kuma, Ehime, Japan) was the first person to spot the comet, when he found it low in the eastern morning sky on December 27. He was using his 20-cm reflector and gave the magnitude as 7.0. On the 28th, A. Hale (Las Cruces, New Mexico, USA) saw the comet using his 20-cm reflector and estimated the magnitude as 7.5. He added that the comet was then at a low altitude in twilight. These observations were confirmed by other observers during the remainder of December, who gave magnitudes around 7. The coma was generally described as moderately condensed and 3–40 across. The observed tail lengths ranged between 0.11
and 0.4
. The comet was well observed in January. W. C. Morrison (Peterborough, Ontario, Canada) observed the comet on seven nights between the 2nd and 27th, using a 15-cm refractor and 7  35 binoculars. He reported magnitudes hovering between 6.7 and 7.1, while giving 6.4 on the last date. S. Mitsuma (Honjo, Saitama, Japan) observed the comet on six nights between the 10th and 29th, using 20  120 binoculars. He estimated magnitudes between 7.0 and 7.3. The coma was generally described as moderately condensed throughout the month, while the diameter was typically 4–60 . The majority of observers reported a tail 18200 , and extended toward about PA 295
. The denser tail 359

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extended about 6400 toward PA 292
. Meech used the 402-cm reflector at Cerro Tololo to acquire two CCD images of the comet on March 7. Farnham (2012) said the two tails were again visible. He wrote, “The broad component is fainter near the nucleus” and extended >27000 toward about PA 280
. Farnham continued, “The dense tail is shorter than in Jan, but still follows the anti-solar direction, putting it at a very different PA than the broad tail.” He said this tail extended about 2900 in PA 234
. Meech requested the assistance of other observers in June. In response, B. E. A. Mueller (Kitt Peak National Observatory, Arizona, USA) acquired CCD images on June 4, using the 213-cm reflector, while E. Hu and L. Cowie (Mauna Kea) acquired CCD images on June 6, using the 224-cm reflector. The total integration times were 2460 seconds on the 4th and 2400 seconds on the 6th, yet there was no trace of a coma or tail, just the stellar nucleus. Meech and Farnham acquired CCD images of the comet on August 2 and 3 using the 224-cm reflector at Mauna Kea. These images had a total integration time of 1200 seconds and 2400 seconds, but, again, no trace of a coma or tail was present. In the course of this year, the comet reached a maximum elongation of 154
on March 16 and a minimum elongation of 14
on November 1. The comet began the year moving in a northerly direction, but after attaining a declination of +27
on April 7 it began moving southward. After having moved southward since last April, the comet attained a declination of 5
on 1993 January 15 and then began a northward motion. The comet reached a maximum elongation of 159
on May 19. The first observations made during 1993 came from Scotti, when he acquired five CCD images on May 29. He noted a magnitude of 20.8–21.0. After having moved northward since mid-January, the comet attained a declination of +1
on June 1 and then began a southerly motion. Scotti acquired three CCD images on June 27, giving the magnitude as 21.3–21.7. The final observations were made during 1993 July 22.21–22.23, when Scotti acquired three CCD images using a 91-cm reflector. He gave the magnitude as 21.9. The comet’s position was α = 15h 30.9m, δ = 1
180 (2000) on the final image. The comet passed aphelion on 1995 February 24. Multiple apparition orbits have been calculated by S. Nakano (1996, 2001), G. V. Williams (1999), and K. Kinoshita (2000, 2005, 2010, 2012). All of the orbits included full planetary perturbations, while those published from 1999 onward also solved for nongravitational effects. The result was a perihelion date of October 2.72 and a period of 6.82 years. The nongravitational terms were within the following ranges: A1 = +0.01 to +0.03 and A2 = 0.0005 to 0.0001. The orbit of Nakano (2001) is given below. T ω Ω (2000.0) i q e 1991 Oct. 2.7171 (TT) 329.0761 122.1341 17.8840 1.437828 0.600050

360

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absolute magnitude: H0 = 14.4, n = 2.3 (Meyer) full moon: May 1, May 31, Jun. 29, Jul. 29, Aug. 27, Sep. 25, Oct. 25, Nov. 23, Dec. 23, 1989 Jan. 21, Feb. 20, Mar. 22, Apr. 21, May 20, Jun. 19, Jul. 18, Aug. 17, Sep. 15, Oct. 14, Nov. 13, Dec. 12, 1990 Jan. 11, Feb. 9, Mar. 11, Apr. 10, May 9, Jun. 8, Jul. 8, Aug. 6, Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30, Apr. 28, May 28, Jun. 27, Jul. 26, Aug. 25, Sep. 23, Oct. 23, Nov. 21, Dec. 21, 1992 Jan. 19, Feb. 18, Mar. 18, Apr. 17, May 16, Jun. 15, Jul. 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6, Mar. 8, Apr. 6, May 6, Jun. 4, Jul. 3. Aug. 2 sources: D. W. E. Green, MPC, No. 13040 (1988 May 1); K. J. Meech, MPC, Nos. 13356, 13364 (1988 Aug. 27); K. J. Meech, MPC, No. 15604 (1990 Jan. 11); D. W. E. Green, ICQ, 12 (1990 Jun.), p. H42; K. J. Meech, MPC, No. 16295 (1990 Jun. 8); K. J. Meech, MPC, No. 16935 (1990 Oct. 4); [Palomar], MPC, Nos. 17086, 17088 (1990 Nov. 2); T. Seki, MPC, No. 18490 (1991 Aug. 25); D. D. Balam and J. B. Tatum, MPC, No. 18666 (1991 Sep. 23); J. V. Scotti, MPC, Nos. 18851, 18854 (1991 Oct. 23); R. J. Modic, ICQ, 14 (1992 Apr.), pp. 32, 43; D. D. Balam, MPC, No. 19912 (1992 Apr. 17); J. Armstrong, ICQ, 15 (1993 Jan.), p. 5; J. V. Scotti, MPC, No. 22278 (1993 Aug. 2); J. V. Scotti, MPC, No. 22439 (1993 Sep. 1); J. V. Scotti, ICQ, 15 (1993 Oct.), p. 166; K. J. Meech, B. E. A. Mueller, E. Hu, L. Cowie, and T. L. Farnham, K. J. Meech correspondence with G. W. Kronk (1994); T. L. Farnham, Modeling Cometary Dust Tails with a Pseudo-Finson-Probstein Technique. Unpublished doctoral dissertation, University of Hawaii, Honolulu, USA (1996); S. Nakano, Nakano Note, No. 624 (1996 May 4); G. V. Williams, CCO, 13th ed. (1999), pp. 68–9; K. Kinoshita correspondence with G. W. Kronk (2000, 2005, 2010, 2012); S. Nakano, Nakano Note, No. 822 (2001 Dec. 20); T. L. Farnham correspondence with G. W. Kronk (2012). C/1988 L1 Discovered: 1988 June 11.40 (Δ = 3.89 AU, r = 4.48 AU, Elong. = 120
) (Shoemaker– Last seen: 1990 March 25.39 (Δ = 3.69 AU, r = 3.87 AU, Elong. = 93
) Holt–Rodriquez) Closest to the Earth: 1989 June 13 (2.0714 AU) Calculated path: SGE (Disc), AQL (Jul. 5), SER (Aug. 27), AQL (Sep. 4), SCT 1989 V=1988h (Sep. 25), SGR (Nov. 17), CAP (1989 Jan. 30), SGR (Feb. 3), MIC (Feb. 14), GRU (Mar. 27), TUC (May 12), HYI (Jun. 7), MEN (Jun. 27), VOL (Jul. 10), CAR (Aug. 9), VOL (Dec. 11), CAR (Dec. 30), PUP (1990 Feb. 13), COL (Mar. 3) In the course of the Palomar Asteroid and Comet Survey, C. S. Shoemaker (Palomar Observatory, California, USA) found a comet on films exposed on 1988 June 11.40 and June 12.33 by H. E. Holt, H. R. Holt, and T. A. Rodriquez using the 46-cm Schmidt telescope. The magnitude was estimated as 13. Shoemaker said the comet exhibited a strong central condensation and a compact coma that mainly extended toward the west. The position on the first image was α = 20h 16.8m, δ = +18
310 (2000). The comet was confirmed by J. B. Gibson (Palomar Observatory), when he acquired 361

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six CCD images during June 25.29–25.49 using the 152-cm reflector. He estimated the magnitude as 15. The comet was discovered almost exactly one year prior to passing perihelion. Numerous photographs of the comet were obtained by several observatories during July. T. Seki (Geisei, Kochi, Japan) was using his 60-cm reflector and estimated the magnitude as 15.5 and 15 on the 6th and 10th, respectively. G. Schwartz (Oak Ridge Observatory, Massachusetts, USA) obtained a 22-minute exposure using the 155-cm reflector on the 11th. He estimated the magnitude as 16 and noted the comet was “very highly condensed.” Also on the 11th, E. F. Helin, J. T. Alu, B. P. Roman, and E. J. Majkowski (Palomar Observatory) photographed the comet using the 46-cm Schmidt telescope and estimated the magnitude as 15.0. On the 13th and 24th, K. Endate and Y. Yanai (Kitami, Hokkaido, Japan) estimated the photographic magnitude as 14. R. Chanal (Aurec-sur-Loire, France) obtained images using a 41-cm reflector and estimated the magnitude as 14.5 on the 16th and 18th. H. R. Holt and Rodriquez (Palomar Observatory) obtained an image using the 46-cm Schmidt telescope on the 17th and estimated the magnitude as 14. E. P. Bus (Netherlands) photographed the comet using a 52-cm reflector on the 24th. He gave the magnitude as 13.4 and noted a strongly condensed coma 0.430 across. Two visual observations were also reported. A. Boattini (Florence, Italy) saw it on the 8th, using his 40-cm reflector. He gave the magnitude as 14.0 and said the coma was moderately condensed and 0.50 across. D. H. Levy (Catalina Station, Mt. Bigelow, Arizona, USA) spotted the comet using the 154-cm reflector on the 12th. He estimated the magnitude as 14.0 and noted a moderately condensed coma 10 across. The comet reached a maximum elongation of 145
on July 24. Four visual observers followed the comet in August. S. Baroni (Milan, Italy) and Boattini observed together on three nights, using a 33-cm reflector. They gave the magnitude as 13.6 on the 12th, 13.7 on the 13th, and 13.6 on the 17th. The coma was slightly condensed on the 12th and 13th, with a diameter of 1.20 , while it was moderately condensed on the 17th and 10 across. A. Hale (Las Cruces, New Mexico, USA) saw the comet using his 41-cm reflector on the 13th and 21st. He gave the magnitude as 13.7 and 13.8, respectively. For the first night, Hale noted, “comet small and very condensed, appearance quite stellar at low power.” R. A. Keen (Mt. Thorodin, Colorado, USA) was observing with his 32-cm reflector on the 14th. He gave the magnitude as 13.8 and said the coma was very slightly condensed and 0.70 across. Boattini saw the comet with a 33-cm reflector on August 18 and gave the magnitude as 13.5. He said the coma was slightly condensed and 10 across. A few visual observations were reported during September. The comet was seen by J. E. Bortle (Stormville, New York, USA), Hale, and S. Korth (Düsseldorf, Germany) on the 7th. Bortle was using his 50-cm reflector and gave the magnitude as 13.6. He said the coma was 0.40 across with a strong 362

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condensation. Hale also gave the magnitude as 13.6 and noted a strong condensation. Korth was using a 36-cm reflector and gave the magnitude as 13.4. He said the coma was moderately condensed and 0.30 across. On the 8th, Korth estimated the magnitude as 13.5. He added that the coma was moderately condensed and 0.30 across. A. Nakamura (Kuma, Ehime, Japan) observed with his 20-cm reflector on the 9th, giving the magnitude as 13.4. He said the coma was moderately condensed and 1.00 across. Bortle gave the magnitude as 13.4 on the 14th and noted a moderately condensed coma 0.50 across. The magnitude was given as 13.7 on the 15th, while the coma was strongly condensed. On the 17th, Keen gave the magnitude as 13.6. He said the coma was very slightly condensed and 1.20 across. The comet had continually moved southward since its discovery, steadily decreasing in altitude. As a result of its faintness, this made it more challenging to observe as October progressed. Throughout the month it was at its highest over the southwestern horizon at the end of evening twilight. Hale saw the comet on the 2nd and gave the magnitude as 13.8. He noted, “comet somewhat more diffuse than during previous observations.” R. J. Bouma (Netherlands) observed with his 51-cm reflector on the 4th and 8th, giving the magnitude as 13.4 and 13.3, respectively. On both occasions, he noted a moderately condensed coma 0.40 across. On the 9th, Keen determined the magnitude as 13.5. He said the coma was uncondensed and 0.90 across. C. S. Morris (Pine Mountain Club, California, USA) saw the comet with his 26-cm reflector on the 31st. He gave the magnitude as 13.6 and the coma diameter as 0.80 . The comet’s continued southerly motion and decreasing elongation made it very difficult to observe as November began. Morris observed the comet on the 5th. He gave the magnitude as 13.6 and said the coma was slightly condensed and 0.60 across. This was the last visual observation of 1988. Meanwhile, two observatories managed to photograph the comet during the early days of November. A. Mrkos and Z. Vávrová (Klet Observatory, Czech Republic) obtained two photographs of the comet on both the 4th and 5th, but provided no physical description. R. E. McCrosky (Oak Ridge Observatory, Massachusetts, USA) obtained the final observation of the comet for 1988, when he found it on a 20-minute exposure that was acquired with the 155-cm reflector on the 6th. The comet was then situated 20
above the southwest horizon in the evening sky. No physical description was provided. At the beginning of 1989, the comet was lost in the Sun’s glare and reached a minimum elongation of 4
on January 13. Two Southern Hemisphere observatories managed to photograph the comet in the morning sky during March and April. Astronomers at Siding Spring Observatory (New South Wales, Australia) photographed the comet on March 9, March 19, and April 18. They estimated the magnitude as 13 on the first date, adding that the comet was strongly condensed, with a tail in PA 225
that curved to PA 280
at a distance of 50 from the coma. A. C. Gilmore and 363

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P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) used a 61-cm reflector to obtain two photographs of the comet on April 4 and gave the magnitude as 13.9. The first visual observations of 1989 came in May. D. A. J. Seargent (Australia) and A. R. Pearce (Australia) observed the comet on the 5th. Seargent was using his 15-cm reflector and gave the magnitude as 11.7. Pearce was using his 20-cm reflector and gave the magnitude as 11.4. Pearce also noted a moderately condensed coma 20 across. A. F. A. L. Jones (Nelson, New Zealand) observed the comet on the 8th, 9th, 10th, and 12th with his 32-cm reflector. He gave the magnitude as 12.2 on the first two nights and 12.1 on the last two nights. Jones said the coma was uncondensed and 0.5–0.60 across. On the 10th and 12th, Pearce determined the magnitude as 11.8 and 11.3, respectively. He said the coma was moderately condensed and 1.5–20 across. Seargent observed the comet on the 31st and gave the magnitude as 11.6. Gilmore and Kilmartin photographed the comet twice on May 13 and gave the nuclear magnitude as 15.7. The comet was at its brightest in June, as it was at its closest distance to both the Sun and Earth. Pearce saw the comet on five nights spanning the 4th to the 24th. He generally gave the magnitude as 11.3 from the 4th to the 9th, while it was 11.7 on the 24th. The coma was slightly condensed and 1.5–2.00 across. Also on the 24th, Pearce noted a “broad fan to the south.” Jones saw the comet on five nights from the 5th to the 30th. He gave the magnitude as 11.4 and 11.5 on the 5th and 6th, respectively, and 12.2–12.4 from the 28th to the 30th. Throughout the month, Jones generally described the coma as slightly condensed and 0.5–0.60 across. Seargent saw the comet on the 7th. He determined the magnitude as 11.8 and said the coma was moderately condensed. Photographs by Gilmore and Kilmartin on the 8th and 29th revealed the nuclear magnitude as 14.5 and 14.6, respectively. The comet reached a maximum elongation of 101
on June 13 and attained its most southerly declination of 74
on June 26. The comet faded in July, as it was now moving away from both the Sun and Earth. P. Camilleri (Australia) saw the comet on the 3rd, 11th, and 27th, using his 20-cm reflector, and gave magnitudes of 11.6, 11.7, and 11.9, respectively. He described the coma as moderately condensed and 4–50 across. Pearce saw the comet during the 3rd to the 5th, giving the magnitude as 11.8–11.9. He added that the coma was slightly condensed and 1.5–1.80 across. Jones saw the comet on the 1st, 6th, and 8th, giving magnitudes of 12.2, 12.0, and 11.8, respectively. He indicated that on all three nights, the comet was uncondensed and 0.50 across. Few observations were made during the remainder of 1989. Pearce obtained the last visual observations on August 31 and September 4. On both nights, he gave the magnitude as 13.0 and said the coma was slightly condensed. Photographs by Gilmore and Kilmartin on September 2 and December 5 revealed nuclear magnitudes of 16.4 and 16.9, respectively. 364

cometography: a catalog of comets

R. H. McNaught (Siding Spring Observatory) photographed the comet on October 29, using the 51-cm Uppsala Southern Schmidt telescope, and estimated the magnitude as 15. After having moved northward since late June, the comet attained a declination of 60
on September 23 and then turned southward. After attaining a declination of 65
on December 13, the comet again turned northward. It reached a minimum elongation of 63
on October 9. The only physical descriptions to be reported in 1990 came from Gilmore and Kilmartin, when their photographs revealed nuclear magnitudes of 17.5 on January 26 and 17.6 on February 27. The comet reached a maximum elongation of 104
on February 13. The final observations of this comet were made on 1990 March 25.37 and March 25.39, when Gilmore acquired exposures of 20 and 30 minutes, respectively, using a 61-cm reflector. The comet’s nuclear magnitude was given as 18.0. The position on the last photograph was α = 6h 26.8m, δ = 34
060 (2000). The first parabolic orbit was calculated by B. G. Marsden and was published on 1988 June 27. It used six positions from June 11–25 and determined the perihelion date as 1989 June 10.99. D. W. E. Green calculated an orbit that was published on July 19. He used 13 positions from June 11 to July 16 and determined the perihelion date as June 12.48. The first hyperbolic orbit was calculated by Marsden and was published on November 23. He used 85 positions from June 11 to October 14 and included perturbations by all nine planets. The result was a perihelion date of June 12.45 and an eccentricity of 1.00059. T. Kobayashi (1989) took 98 positions from 1988 June 11 to 1989 April 18 and included perturbations by all nine planets. He determined the perihelion date as June 12.47 and the eccentricity as 1.00054. Marsden (1990) calculated the original and future orbits based on this orbit and found both to be elliptical with periods of about 550 thousand years and 237 thousand years, respectively. K. Muraoka (1991) took 133 positions from the entire period of visibility and included perturbations by all nine planets. He determined a hyperbolic orbit with a perihelion date of June 12.46 and an eccentricity of 1.00057. This orbit is given below. The 7th edition of Marsden’s Catalogue of Cometary Orbits included original and future orbits for this comet. Both were elliptical with a period of about 624 thousand years and 255 thousand years, respectively. T ω Ω (2000.0) i q e 1989 Jun. 12.4596 (TT) 232.1427 115.2561 97.6929 2.474368 1.000567

absolute magnitude: H0 = 8.0, n = 2.1 (Kronk) full moon: May 31, Jun. 29, Jul. 29, Aug. 27, Sep. 25, Oct. 25, Nov. 23, Dec. 23, 1989 Jan. 21, Feb. 20, Mar. 22, Apr. 21, May 20, Jun. 19, Jul. 18, 365

cometography: a catalog of comets

Aug. 17, Sep. 15, Oct. 14, Nov. 13, Dec. 12, 1990 Jan. 11, Feb. 9, Mar. 11, Apr. 10 sources: G. Schwartz and R. E. McCrosky, HOPL (1988); C. S. Shoemaker, H. E. Holt, H. R. Holt, and T. A. Rodriquez, IAUC, No. 4618 (1988 Jun. 25); J. B. Gibson and B. G. Marsden, IAUC, No. 4619 (1988 Jun. 27); A. Boattini, ICQ, 10 (1988 Jul.), p. 85; T. Seki, E. F. Helin, J. T. Alu, B. P. Roman, E. J. Majkowski, and D. W. E. Green, IAUC, No. 4631 (1988 Jul. 19); C. S. Shoemaker, H. E. Holt, H. R. Holt, T. A. Rodriquez, J. B. Gibson, T. Seki, G. Schwartz, E. F. Helin, J. T. Alu, B. P. Roman, E. J. Majkowski, K. Endate, and Y. Yanai, MPC, Nos. 13363–4 (1988 Aug. 27); A. Boattini, S. Baroni, A. Hale, and S. Korth, ICQ, 10 (1988 Oct.), p. 119; A. Boattini, S. Baroni, R. A. Keen, A. Hale, J. E. Bortle, and S. Korth, IAUC, No. 4658 (1988 Oct. 4); R. Chanal, MPC, No. 13639 (1988 Oct. 25); R. A. Keen and C. S. Morris, IAUC, No. 4675 (1988 Nov. 14); B. G. Marsden, MPC, No. 13843 (1988 Nov. 23); A. Mrkos, Z. Vávrová, and R. E. McCrosky, MPC, No. 13927 (1988 Dec. 23); A. Hale, R. A. Keen, J. E. Bortle, and C. S. Morris, ICQ, 11 (1989 Jan.), pp. 9, 20; [Siding Spring], MPC, Nos. 14390–1 (1989 Apr. 21); [Siding Spring], A. C. Gilmore, and P. M. Kilmartin, MPC, No. 14521 (1989 May 20); A. C. Gilmore, P. M. Kilmartin, and T. Kobayashi, MPC, Nos. 14821, 14904 (1989 Aug. 17); E. P. Bus, R. J. Bouma, D. A. J. Seargent, A. R. Pearce, A. F. A. L. Jones, and P. Camilleri, ICQ, 11 (1989 Oct.), p. 42; A. C. Gilmore and P. M. Kilmartin, MPC, No. 15133 (1989 Oct. 14); R. H. McNaught, MPC, No. 15441 (1989 Dec. 12); A. R. Pearce, ICQ, 12 (1990 Apr.), p. 48; B. G. Marsden, AJ, 99 (1990 Jun.), p. 1972; A. Nakamura, ICQ, 12 (1990 Jul.), p. 87; A. C. Gilmore, MPC, No. 16654 (1990 Aug. 6); K. Muraoka, MPC, No. 17791 (1991 Feb. 28); A. C. Gilmore and P. M. Kilmartin, MPC, No. 18010 (1991 Apr. 28); D. H. Levy, ICQ, 13 (1991 Jul.), p. 114; B. G. Marsden, CCO, 7th ed. (1992), p. 97; A. C. Gilmore, P. M. Kilmartin correspondence with G. W. Kronk (2011). 67P/ Recovered: 1988 July 6.35 (Δ = 2.45 AU, r = 3.44 AU, Elong. = 163
) Churyumov– Last seen: 1991 May 16.23 (Δ = 4.02 AU, r = 4.98 AU, Elong. = 159
) Gerasimenko Closest to the Earth: 1990 February 27 (1.9341 AU) Calculated path: SGR (Rec), CAP (Nov. 23), AQR (1989 Jan. 25), PSC 1989 VI=1988i (Mar. 18), CET (Mar. 29), PSC (Apr. 9), ARI (May 2), TAU (May 26), GEM (Jul. 7), CNC (Aug. 9), LEO (Sep. 5), VIR (Nov. 6), LIB (1990 Dec. 12), VIR (1991 Apr. 28) B. G. Marsden (1987) provided the prediction for this return. He used 69 positions from 1969–1982, included full planetary perturbations, and solved for nongravitational effects. He then integrated the comet’s motion to this apparition and predicted the comet would pass perihelion on 1989 June 18.40.

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cometography: a catalog of comets

The comet was independently recovered at two separate observatories. J. B. Gibson (Palomar Observatory, California, USA) acquired three CCD images of the comet during 1988 July 6.35–6.37 using the 152-cm reflector and a Gunn r filter. The comet was described as essentially stellar and the magnitude was estimated as 20. The position on the first image was α = 20h 13.0m, δ = 29
080 (2000). Gibson acquired three additional images during July 7.36–7.37, noting no change in the comet’s appearance. Meanwhile, H. Pedersen (La Silla Observatory, Chile) found the comet on a photographic plate exposed on July 10.15 with the 220-cm reflector. He also reported the comet was essentially stellar and determined the nuclear magnitude as 18.2. The comet reached a maximum elongation of 171
on July 18 and attained its most southerly declination of 31
on August 22. The only additional observations made during 1988 came from K. J. Meech (Mauna Kea, Hawaii, USA) when she acquired three CCD images during September 12.31–12.34 using the 224-cm reflector. Meech gave the nuclear magnitude as 18.6. The comet was not observed during the next two years. The elongation varied from 4
on 1989 March 18, to 172
on 1990 March 21, and then 3
on 1990 October 17, while the declination varied from +26
on 1989 July 16, to +3
on 1990 January 12, and then +9
on 1990 April 23. The comet was heading southward as 1991 began, attaining a declination of 14
on February 18 before starting a northward motion. It reached a maximum elongation of 178
on April 27. The final observations of this comet were made during May 15.21–15.23 and May 16.20–16.23, when B. E. A. Mueller (Kitt Peak National Observatory, Arizona, USA) acquired five and six CCD images, respectively, using the 213-cm reflector. She gave the nuclear magnitude as 22.0 on the 15th and 21.8 on the 16th. The comet’s position on the final image was α = 14h 09.9m, δ = 11
020 (2000). Multiple apparition orbits have been calculated by G. Forti (1989), D. K. Yeomans and P. W. Chodas (1989), S. W. Milbourn (1993), B. G. Marsden (1997), K. Kinoshita (1998, 2003, 2004, 2009), and S. Nakano (2003, 2006). These included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of June 18.39 and a period of 6.59 years. The nongravitational terms were within the following ranges: A1 = +0.01 to +0.10 and A2 = +0.0075 to +0.0107. The orbit of Nakano (2006) is given below. T ω Ω (2000.0) i q e 1989 Jun. 18.3918 (TT) 11.4245 51.0115 7.1183 1.299684 0.630254

absolute magnitude: H10 = 11.5 (Meyer) full moon: Jun. 29, Jul. 29, Aug. 27, Sep. 25, Oct. 25, Nov. 23, Dec. 23, 1989 Jan. 21, Feb. 20, Mar. 22, Apr. 21, May 20, Jun. 19, Jul. 18, Aug. 17, Sep. 15,

367

cometography: a catalog of comets

Oct. 14, Nov. 13, Dec. 12, 1990 Jan. 11, Feb. 9, Mar. 11, Apr. 10, May 9, Jun. 8, Jul. 8, Aug. 6, Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30, Apr. 28, May 28 sources: B. G. Marsden, MPC, No. 11502 (1987 Jan. 15); B. G. Marsden, BAA Handbook for 1988 (1987 Oct.), p. 81; J. B. Gibson and H. Pedersen, IAUC, No. 4625 (1988 Jul. 11); J. B. Gibson and H. Pedersen, MPC, No. 13364 (1988 Aug. 27); B. G. Marsden, BAA Handbook for 1989 (1988 Oct.), p. 76; K. J. Meech, MPC, No. 13783 (1988 Nov. 23); G. Forti, AAP, 215 (1989 May), pp. 383–6; D. K. Yeomans and P. W. Chodas, CCO, 6th ed. (1989), pp. 33, 65, 70; D. K. Yeomans and P. W. Chodas, AJ, 98 (1989 Sep.), pp. 1083–93; B. E. A. Mueller, MPC, Nos. 18491–2 (1991 Aug. 25); S. W. Milbourn, CCO, 8th ed. (1993), pp. 35, 69, 76; B. G. Marsden, CCO, 12th ed. (1997), pp. 66–7; K. Kinoshita correspondence with G. W. Kronk (1998, 2003, 2004, 2009); S. Nakano, Nakano Note, No. 1008 (2003 Dec. 7); S. Nakano, Nakano Note, No. 1310 (2006 Apr. 7). C/1988 M1 Discovered: 1988 June 27.64 (Δ = 1.03 AU, r = 0.03 AU, Elong. = 1.2
) (SMM 3) Last seen: 1988 June 27.72 (Δ = 1.02 AU, r = 0.02 AU, Elong. = 0.8
) Closest to the Earth: 1988 June 27 (1.0124 AU) 1988 X=1988l Calculated path: GEM (Disc) [Did not leave this constellation] O. C. St. Cyr (NASA Goddard Space Flight Center, Greenbelt, Maryland, USA) spotted this comet during a routine inspection of the coronagraph/ polarimeter images obtained by the Solar Maximum Mission (SMM). The head of the comet was first visible on 1988 June 27.64, and the position was given as α = 6h 22.8m, δ = +22
450 (2000). The comet’s head was observed for the final time on June 27.72, and the position was then given as α = 6h 24.6m, δ = +23
120 (2000). The comet was not detected as it receded from the Sun. Overall, the comet was visible on seven images. Although the initial magnitude estimate was given as 1 at the time this comet’s discovery was announced, R. Kracht (2015) notes that the comet is much fainter than Mercury appears in other SMM images. Since Mercury’s magnitude was 2, he estimates that SMM 3 “not brighter than a star of mag 4.” B. G. Marsden (1988) was able to calculate a Kreutz-type parabolic orbit, with a perihelion date of 1988 June 27.78. Marsden (1989) calculated a very similar orbit, which is given below. T 1988 Jun. 27.784 (TT)

ω 85.882

Ω (2000.0) 7.660

i 144.706

q 0.00516

e 1.0

sources: O. C. St. Cyr and B. G. Marsden, IAUC, No. 4648 (1988 Aug. 30); B. G. Marsden, AJ, 98 (1989 Dec.), pp. 2308–9; R. Kracht correspondence with G. W. Kronk (2015).

368

cometography: a catalog of comets

C/1988 P1 Discovered: 1988 August 6.47 (Δ = 1.14 AU, r = 1.19 AU, Elong. = 67
) (Machholz) Last seen: 1988 October 6.04 (Δ = 1.20 AU, r = 0.64 AU, Elong. = 32
) Closest to the Earth: 1988 August 28 (0.8626 AU) 1988 XV=1988j Calculated path: ORI (Disc), MON (Aug. 19), HYA (Aug. 30), SEX (Sep. 8), LEO (Sep. 14), VIR (Sep. 17) D. E. Machholz (Loma Prieta, California, USA) discovered this comet using homemade 27  120 binoculars on 1988 August 6.47, at a position of α = 4h 43.9m, δ = +0
450 (2000). He determined the magnitude as 8.6 and described the comet as diffuse, with some condensation, and 3–50 across. He had spent 475 hours searching for comets since his discovery of comet 96P/1986 J2. The comet was confirmed by C. S. Morris (near Mt. Wilson, California, USA) on August 7.47, Machholz on August 7.48, and D. H. Levy (Tucson, Arizona, USA) on August 7.49. Morris gave the magnitude as 9.6, using his 26-cm reflector, and 9.3, using 20  80 binoculars. The binoculars also revealed a coma 5.60 across. Machholz gave the magnitude as 8.6. Levy gave the magnitude as 8.7, using his 41-cm reflector. He noted a slightly condensed coma 30 across and a possible tail toward PA 270
. Independent discoveries were made by K. Takamizawa (Saku, Nagano, Japan) on August 8.738, T. Yanaka (Motegi, Tochigi, Japan) on August 8.746, M. Terasako (Hamamatsu, Shizuoka, Japan) on August 8.754, R. Irie (Toyooka, Hyogo, Japan) on August 8.785, and S. Fujikawa (Onohara, Kagawa, Japan) on August 8.794. Each of these observers estimated the magnitude as 9 and said the comet was diffuse and centrally condensed. The comet was well observed during the remainder of August, with over 130 observations being reported to the International Comet Quarterly. Machholz was the most prolific observer, as he saw the comet on 13 nights spanning the 8th to the 30th. He mostly used his 13-cm refractor from the 8th to the 27th and reported the comet brightened from magnitude 8.6 to 7.8. The coma was moderately condensed during this period, while the coma remained 50 in diameter through most of the month. Machholz observed with his 15-cm reflector on the 30th, giving the magnitude as 7.5 and the coma diameter as 30 . A tail was detected on the 22nd and 25th while Machholz used his 13-cm refractor. He said it extended 100 in PA 256
on the first night and 150 in PA 250
on the second night. T. Lovejoy (Shailer Park, Queensland, Australia) saw the comet on 11 nights from the 8th to the 29th. Using his 15  80 binoculars, he reported the comet brightened from magnitude 8.1 to 6.2. He consistently noted a strongly condensed coma during the last half of the month, which was 80 across on the 11th and 50 across during the 16th to the 19th. Lovejoy also noted a tail, which the binoculars revealed had increased in length from 0.3
to 0.7
from the 8th to the 25th; however, moonlight on the 28th reduced the length to 0.3
. D. A. J. Seargent (The Entrance, New South Wales, Australia) saw the comet on four nights spanning the 13th to the 24th, using 15  80 binoculars.

369

cometography: a catalog of comets

He indicated that the magnitude brightened from 8.0 to 6.4. Seargent also said the coma was slightly condensed on the 13th, but was strongly condensed by the 24th. He noted a tail extending about 40 in PA 290
on the 24th. The comet attained its most southerly declination of 2
on September 1. On that same night, Machholz and A. R. Pearce (Australia) saw the comet. Machholz was using his 15-cm reflector and gave the magnitude as 7.5. He noted the coma was slightly condensed and 30 across. Pearce was using his 20-cm reflector and gave the magnitude as 7.4. He reported a moderately condensed coma. Seargent saw the comet on the 2nd, giving the magnitude as 6.1 and noting a strongly condensed coma. He added that his 25-cm reflector revealed a broad tail with a central spine. Morris and R. H. McNaught (Coonabarabran, New South Wales, Australia) saw the comet on the 3rd. Morris was using 20  80 binoculars and estimated the magnitude as 6.0. McNaught was using 9  63 binoculars and gave the magnitude as 7.4. He added that the coma was moderately condensed and 10 across, while the tail was 0.2
long. The last astrometric positions were obtained on September 4.80, when McNaught (Siding Spring Observatory, New South Wales, Australia) acquired three images while using the 51-cm Uppsala Southern Schmidt telescope. No physical descriptions were provided. The position on the last image was α = 9h 04.8m, δ = 1
380 (2000). Visual observers continued to follow the comet in the nights that followed. A. Hale (Las Cruces, New Mexico, USA) and Seargent saw the comet on September 6. Hale was using his 41-cm reflector and gave the magnitude as 7.0. Seargent gave the magnitude as 6.6. He added that his 25-cm reflector revealed a tail extending 0.2
in PA 248
. Hale tried to see the comet when it was 24
from the Sun on the 7th, both with and without a Swan-band filter, but was unsuccessful. He suggested it was fainter than about magnitude 6. J. G. de Souza Aguiar (Campinas, Sao Paulo, Brazil) was able to find the comet with his 25-cm reflector on the 11th, giving the magnitude as 5.0. He said the coma was slightly condensed and 2.90 across, while the tail extended 240 in PA 35
. Hale tried to spot the comet with 10  50 binoculars on the 17th when it was about 2.5
from the Sun, but was unsuccessful. He estimated that the comet was fainter than 2. The comet reached a minimum elongation of 1
on September 18. Several observers tried to find the comet from the 24th to the 30th, but without success. J. E. Bortle (Stormville, New York, USA) was the observer on the last date, when the comet was 24
from the Sun near the end of evening twilight. It was then 6
above the western horizon. He carefully searched using 20  80 binoculars, but said it must have been fainter than magnitude 8.0. After having moved northward since the beginning of the month, the comet attained a declination of +4
on September 27 and then began a southward motion. O. C. St. Cyr (High Altitude Observatory, Boulder, Colorado, USA) examined images obtained with the coronagraph/polarimeter about the 370

cometography: a catalog of comets

Solar Maximum Mission spacecraft during the period of September 17.88 to 18.83. Even though the comet was predicted to pass through the field during this period, no trace was found. Based on the detection of Beta Virginis, which was magnitude 3.6, St. Cyr concluded the comet was fainter than magnitude 4. Hale and Machholz were unsuccessful in locating the comet on October 1 and Machholz was again unsuccessful on the 3rd; however, M. Jäger (Fischamend, Austria) announced that he had photographed the comet using his 20-cm reflector on October 3.76. He estimated the magnitude as 12.01.0 and noted a diffuse coma 30 across. Possible observations were also reported by G. W. Kronk (Collinsville, Illinois, USA) on October 5.05 and October 6.04. Kronk was using his 33-cm reflector and an eyepiece giving a power of 122. He checked the comet’s predicted position on the 5th. Although he initially found nothing, he then attached a light pollution filter to the lens and found an uncondensed, oblong object of about magnitude 11.5 that measured 30 by 40 . Glimpses were seen with averted vision over a period of 10 minutes. Kronk star-hopped to the comet’s predicted position on the 6th and again found nothing; however, attaching the light pollution filter to the lens, he noticed a round, very slightly condensed object of magnitude 11.5 that was visible between the center and edge of the field using averted vision. It was observed for about 15 minutes, with the last 5 minutes being the most difficult because of the comet’s low altitude. No further observations were reported. On October 13.1, S. Wyckoff and S. Tegler (Kitt Peak National Observatory, Arizona, USA) obtained two five-minute integrations using the 229-cm reflector, a CCD camera, and a Mould R filter. The field of view of the images was 20 by 20 , but no trace of the comet was found. They concluded it was fainter than magnitude 20. On October 13.14, R. E. Royer (Wrightwood, California, USA) obtained a photograph using his 46-cm reflector. Clear star images to magnitude 16 were present, but no definite image of the comet within about 15’ of the prediction. On October 21.1 and 22.1, J. B. Gibson (Palomar Observatory, California, USA) obtained CCD images of the comet’s predicted position using the 152-cm reflector and a Gunn r filter, which provided fields measuring 8.20 by 8.20 . No cometary candidate was visible down to magnitude 19–20. The first parabolic orbit was calculated by D. W. E. Green and was published on 1988 August 9. He took five positions from August 7–9 and determined a perihelion date of 1988 September 17.22. B. G. Marsden calculated a parabolic orbit that was published on August 19. He took 26 positions obtained during August 7–17, and determined the perihelion date as September 17.59. Green published a revised parabolic orbit on September 25. This used 30 positions from August 9 to September 4. The result was a perihelion date of September 17.57. This orbit is given below. 371

cometography: a catalog of comets T 1988 Sep. 17.5682 (TT)

ω 349.0366

Ω (2000.0) 167.7281

i 40.1990

q 0.164558

e 1.0

absolute magnitude: pre-perihelion: H0 = 8.1, n = 2.1, post-perihelion: H10 = 13.1, from visual observations (Meyer) full moon: Jul. 29, Aug. 27, Sep. 25, Oct. 25 sources: D. E. Machholz and C. S. Morris, IAUC, 4636 (1988 Aug. 8); D. W. E. Green, IAUC, No. 4637 (1988 Aug. 9); K. Takamizawa, T. Yanaka, M. Terasako, R. Irie, and S. Fujikawa, IAUC, No. 4641 (1988 Aug. 16); B. G. Marsden, IAUC, No. 4643 (1988 Aug. 19); J. E. Bortle, T. Lovejoy, and D. E. Machholz, IAUC, No. 4644 (1988 Aug. 19); D. A. J. Seargent, J. E. Bortle, and T. Lovejoy, IAUC, No. 4649 (1988 Sep. 1); C. S. Morris, R. H. McNaught, A. Hale, and D. A. J. Seargent, IAUC, No. 4652 (1988 Sep. 14); R. H. McNaught and D. W. E. Green, MPC, Nos. 13493, 13591 (1988 Sep. 25); C. S. Morris, R. H. McNaught, A. Hale, and J. G. de Souza Aguiar, ICQ, 10 (1988 Oct.), pp. 118–19; O. C. St. Cyr and M. Jäger, IAUC, No. 4658 (1988 Oct. 4); S. Wyckoff, S. Tegler, R. E. Royer, and J. B. Gibson, IAUC, No. 4669 (1988 Oct. 28); D. E. Machholz, J. E. Bortle, D. A. J. Seargent, and A. R. Pearce, ICQ, 11 (1989 Jan.), pp. 6, 19; T. Lovejoy, ICQ, 11 (1989 Apr.), pp. 32–3; D. H. Levy, ICQ, 13 (1991 Jul.), pp. 113–14; G. W. Kronk, ICQ, 15 (1993 Jan.), p. 17; D. E. Machholz correspondence with G. W. Kronk (2011). 22P/Kopff Recovered: 1988 February 11.24 (Δ = 3.75 AU, r = 4.72 AU, Elong. = 167
) Last seen: 1991 January 15.10 (Δ = 3.16 AU, r = 3.33 AU, Elong. = 91
) 1990 I=1988k Closest to the Earth: 1990 October 1 (1.8219 AU) Calculated path: CNC (Rec), LEO (Jul. 15), VIR (Dec. 1), LEO (1989 Mar. 9), VIR (Jul. 6), LIB (Oct. 9), SCO (Nov. 17), OPH (Nov. 24), SGR (Dec. 20), CAP (1990 Feb. 2), AQR (Mar. 11), PSC (Apr. 25), CET (May 12), PSC (May 27), CET (Jul. 15), PSC (Oct. 17) A prediction for the return of this comet was calculated by T. Kobayashi (1987). He took 144 positions from 1970–1983, included perturbations by all nine planets, and solved for nongravitational effects. He then integrated the comet’s motion to this apparition and determined the perihelion date as 1990 January 20.39. The comet was recovered on three CCD images acquired by E. M. Alvarez, M. J. S. Belton, and K. J. Meech (Mauna Kea, Hawaii, USA) during 1988 February 11.24–11.26 while using the 224-cm reflector. They gave the comet’s magnitude as about 21 and described the comet as centrally condensed, without any obvious coma. The position on the first image was α = 8h 45.2m, δ = +19
090 (2000). Another three images were obtained by Meech using the same telescope during February 15.23–15.26. Over a month passed before they were able to obtain better confirmation, which came during March 19.23–19.25, March 20.24–20.26, and March 22.23–22.24. 372

cometography: a catalog of comets

The comet was moving northward when recovered; however, after attaining its most northerly declination of +21
on April 8, it began a southward motion. No observations were acquired during the next few months as the comet’s elongation from the Sun decreased, reaching a minimum of 2
on August 18. The only other observations acquired during 1988 came on December 10.59 and December 10.60, when Meech obtained CCD images using the 224-cm reflector. No descriptive information was provided. The comet was moving southward as 1989 began; however, after attaining a declination of +4
on January 6, it began a northward motion. Although several observatories provided astrometric positions throughout the year, only three descriptions were provided. T. Seki (Geisei, Kochi, Japan) obtained two photographs with his 60-cm reflector on March 8 and estimated the magnitude as 18.5. K. Jockers and G. P. Chernova (Hoher List Observatory, Eifel, Germany) used the 106-cm reflector, a focal reducer, and wide-band filters during May 6.88–6.94. They determined the magnitude as 18.50.3 at an effective wavelength of 434nm and 16.60.3 at 680nm. They added, “The comet is significantly redder than the sun.” H. E. Bond (Cerro Tololo Inter-American Observatory, Chile) used the 91-cm reflector to acquire two R-band CCD images on June 2. These showed an extended coma measuring about 1400 by 900 . The comet reached its maximum elongation of 175
on March 11 and its minimum elongation of 2
on December 12. After having moved northward since early January, the comet attained a declination of +12
on May 2 and then began a southward motion. The comet attained its most southerly declination of 22
on December 31. Astronomers at Lowell Observatory’s Anderson Mesa Station (Arizona, USA) were the only observers of this comet during 1990. B. A. Skiff and C. M. Olmstead obtained three CCD images using the 183-cm reflector on July 29. They gave the magnitude as 15.5 and noted “substantial coma” and a tail extending 1.50 toward the west-southwest. On August 28, Skiff obtained two images and gave the magnitude as 15.8. He said the tail began as a fan south of the nucleus, but sharply curved off to form a westward-pointing streamer, which was at least 40 long. Skiff obtained four images on August 29, and gave the magnitude as 16.2. Skiff and T. Polakis obtained three images on both September 22 and September 25. They gave the magnitude as 16.0 on each date. During the remainder of the year, Skiff used the 104-cm reflector and a CCD camera to monitor the comet. He determined the nuclear magnitude as 15.6 during October 23–25, 15.7 on October 26, 17.1 on December 6, and 17.2 on December 7. The comet had been moving northward since last December, but after attaining a declination of +9
on August 12, it began a southward motion. This southward motion ended on November 27, when the comet attained a declination of +3
and then began moving northward again. The comet reached a maximum elongation of 173
on October 23. 373

cometography: a catalog of comets

The comet was last detected on 1991 January 15.09–15.10, when Skiff and two MIT undergraduate students, K. L. Faul and J. R. Pacatte, obtained three CCD images using the 104-cm reflector. The magnitude was given as 18.2 and the position was α = 1h 43.6m, δ = +5
310 (2000) on the last date. Multiple apparition orbits have been calculated by D. K. Yeomans and P. W. Chodas (1989), Nakano (1993, 2003), G. Sitarski (1994), K. Kinoshita (1998, 2003), and P. Rocher (2002, 2003, 2004). All of these calculations included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of January 20.37 and a period of 6.46 years. Most of these astronomers determined standard nongravitational terms within the following ranges: A1 = 0.29 to +0.11 and A2 = 0.1145 to 0.0928. The value of A1 has generally increased from 1970 to 2003. Nakano (1993) and Rocher (2004) found a better fit using three nongravitational terms, with Nakano giving them as A1 = 0.31, A2 = 0.1259, and A3 = 0.17 and Rocher giving them as A1 = +0.08, A2 = 0.1062, and A3 = 0.11. Yeomans and Chodas (1989) examined the motion of several periodic comets. For this comet, they found that an asymmetric model of nongravitational effects “more accurately mimics the comet’s outgassing history” than the symmetric model used for the values in the previous paragraph. G. Sitarski (1994) determined an orbit for this comet that used 804 positions from 1906–1991, included planetary perturbations, and solved for nongravitational effects. The result was a perihelion date of January 20.37 and a period of 6.46 years. The nongravitational effects were based on “the asymmetric nongravitational acceleration model for the rotating and precessing nucleus.” His nongravitational terms for the 1990 apparition were: I = 112.06
, φ = 175.44
, τ = 39.65 days, Ā1 = +0.50918 Ā2 = 0.08253, and Ā3 = 0.10328. This orbit is given below. T ω Ω (2000.0) i q e 1990 Jan. 20.3689 (TT) 162.8936 120.9215 4.7171 1.585152 0.542978

absolute magnitude: H0 = 8.2, n = 5.9 (Meyer) full moon: Feb. 2, Mar. 3, Apr. 2, May 1, May 31, Jun. 29, Jul. 29, Aug. 27, Sep. 25, Oct. 25, Nov. 23, Dec. 23, 1989 Jan. 21, Feb. 20, Mar. 22, Apr. 21, May 20, Jun. 19, Jul. 18, Aug. 17, Sep. 15, Oct. 14, Nov. 13, Dec. 12, 1990 Jan. 11, Feb. 9, Mar. 11, Apr. 10, May 9, Jun. 8, Jul. 8, Aug. 6, Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30 sources: T. Kobayashi, ICQ Special Issue, 9 (1987 Dec.), p. H5; E. M. Alvarez, M. J. S. Belton, and K. J. Meech, IAUC, No. 4647 (1988 Aug. 25); E. M. Alvarez, M. J. S. Belton, and K. J. Meech, MPC, No. 13494 (1988 Sep. 25); T. Seki, MPC, No. 14521 (1989 May 20); K. Jockers and G. P. Chernova, IAUC, No. 4787 (1989 Jun. 1); H. E. Bond, IAUC, No. 4790 (1989 Jun. 2); D. K. Yeomans and P. W. Chodas, AJ, 98 (1989 Sep.), pp. 1083, 1087, 1089; K. J. Meech, MPC, Nos. 16298–9 (1990 Jun. 8); B. A. Skiff 374

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and C. M. Olmstead, MPC, No. 16773 (1990 Sep. 5); B. A. Skiff, MPC, No. 16935 (1990 Oct. 4); B. A. Skiff and T. Polakis, MPC, No. 17086 (1990 Nov. 2); B. A. Skiff, MPC, No. 17488 (1991 Jan. 30); B. A. Skiff and K. L. Faul, MPC, No. 17683 (1991 Feb. 28); S. Nakano, Nakano Note, No. 593 (1993 Apr. 8); G. Sitarski, AcA, 44 (1994), p. 424; K. J. Meech correspondence with G. W. Kronk (1994); P. Rocher correspondence with G. W. Kronk (2002, 2003, 2004); K. Kinoshita correspondence with G. W. Kronk (1998, 2003); S. Nakano, Nakano Note, No. 991 (2003 Nov. 18); T. Polakis, K. L. Faul, and J. R. Pacatte, B. A. Skiff correspondence with G. W. Kronk (2011). C/1988 Q1 Discovered: 1988 August 21.70 (Δ = 1.00 AU, r = 0.02 AU, Elong. = 1.2
) (SMM 4) Last seen: 1988 August 21.75 (Δ = 1.00 AU, r = 0.02 AU, Elong. = 0.7
) Closest to the Earth: 1988 August 21 (1.0022 AU) 1988 XII=1988m Calculated path: LEO (Disc) [Did not leave this constellation] D. Kobe and C. Waugh (NASA Goddard Space Flight Center, Greenbelt, Maryland, USA) spotted this comet during a routine inspection of the coronagraph/polarimeter images obtained by the Solar Maximum Mission (SMM). The head of the comet was first visible on 1988 August 21.70, and the position was α = 9h 59.6m, δ = +11
470 (2000). The magnitude was estimated as 3. The comet’s head was observed for the final time on August 21.75, and the position was α = 10h 02.0m, δ = +11
520 (2000). The comet was detected on two other images, but the head was involved with an electronic blemish and no measurements could be made. The comet was not detected as it receded from the Sun. B. G. Marsden (1988) was able to calculate a Kreutz-type parabolic orbit, with a perihelion date of 1988 August 21.82. A very similar orbit was calculated by Marsden (1989) and this is given below. T 1988 Aug. 21.819 (TT)

ω 82.252

Ω (2000.0) 3.200

i 144.436

q 0.00591

e 1.0

sources: D. Kobe, C. Waugh, and B. G. Marsden, IAUC, No. 4660 (1988 Oct. 5); B. G. Marsden, AJ, 98 (1989 Dec.), pp. 2308–9. C/1988 T1 Discovered: 1988 October 11.88 (Δ = 0.97 AU, r = 0.03 AU, Elong. = 1.2
) (SMM 5) Last seen: 1988 October 12.10 (Δ = 1.00 AU, r = 0.01 AU, Elong. = 0.1
) Closest to the Earth: 1988 October 9 (0.9433 AU) 1988 XVII=1988n Calculated path: VIR (Disc) [Did not leave this constellation] O. C. St. Cyr (NASA Goddard Space Flight Center, Greenbelt, Maryland, USA) spotted this comet during a routine inspection of the coronagraph/ polarimeter images obtained by the Solar Maximum Mission (SMM). The head of the comet was first visible on 1988 October 11.88, and the position was α = 13h 05.4m, δ = 7
470 (2000). The magnitude was estimated as 375

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brighter than 4. The comet’s head was observed for the final time on October 11.97, and the position was α = 13h 08.3m, δ = 7
390 (2000). The head passed behind the occulting disk on October 12.00. Thereafter, several additional images showed only the tail. The comet was completely gone after October 12.10 and it was not detected as it receded from the Sun. Compared to the previous SMM comets, this comet had the longest tail and was the brightest. IAU Circular number 4668 contained the following statement concerning the tail, “There was a conspicuous bulge (almost doubling the width of the tail) on the northern side, about halfway along its length. There appeared to be a wispy structure extending further north and sunward from this bulge, and the wispy structure appears to track with the comet in several images.” B. G. Marsden (1988) was able to calculate a Kreutz-type parabolic orbit, with a perihelion date of 1988 October 12.07. A very similar orbit was calculated by Marsden (1989) and this is given below. T 1988 Oct. 12.072 (TT)

ω 88.083

Ω (2000.0) 10.351

i 144.786

q 0.00513

e 1.0

sources: O. C. St. Cyr and B. G. Marsden, IAUC, No. 4668 (1988 Oct. 25); B. G. Marsden, AJ, 98 (1989 Dec.), pp. 2308–9. C/1988 U1 Discovered: 1988 October 24.68 (Δ = 0.97 AU, r = 0.03 AU, Elong. = 0.8
) (SMM 7) Last seen: 1988 October 24.81 (Δ = 0.98 AU, r = 0.01 AU, Elong. = 0.2
) Closest to the Earth: 1988 October 20 (0.8970 AU) 1988 XIX=1988q Calculated path: VIR (Disc) [Did not leave this constellation] A. L. Stanger (High Altitude Observatory, Boulder, Colorado, USA) spotted this comet during a routine inspection of the coronagraph/polarimeter images obtained by the Solar Maximum Mission (SMM). The head of the comet was visible on 1988 October 24.68 and October 24.75. His measurements allowed D. S. Pitone and B. J. Twambly (SMM Flight Dynamics Facility) to give the position on the first date as α = 13h 54.9m, δ = 12
360 (2000) and the position on the last date as α = 13h 56.8m, δ = 12
270 (2000). Parts of the tail saturated the vidicon detector and it was suggested that the magnitude was brighter than 4. The tail was also described as straight and had a sharp southern edge. The comet’s tail was observed for the final time on October 24.81, when the head was behind the occulting disk. B. G. Marsden (1988) said the positions could be represented by taking the orbit of comet SMM 5 and changing the perihelion date to 1988 October 24.87. He also noted that a better fit occurred with a perihelion date of October 24.88 and changing the perihelion distance from 0.0053 AU to 0.0058 AU. An orbit with a perihelion date of October 24.86 was calculated by Marsden (1989) and this is given below. 376

cometography: a catalog of comets T 1988 Oct. 24.864 (TT)

ω 86.142

Ω (2000.0) 7.981

i 144.716

q 0.00579

e 1.0

sources: A. L. Stanger, D. S. Pitone, B. J. Twambly, and B. G. Marsden, IAUC, No. 4692 (1988 Dec. 17); B. G. Marsden, AJ, 98 (1989 Dec.), pp. 2308–9. 142P/1988 V1 Prediscovery: 1988 October 11.48 (Δ = 1.82 AU, r = 2.73 AU, Elong. = 151
) (Ge–Wang) Discovered: 1988 November 4.60 (Δ = 1.83 AU, r = 2.81 AU, Elong. = 168
) Last seen: 1988 December 13.11 (Δ = 2.16 AU, r = 2.94 AU, Elong. = 135
) 1988 VIII=1988o Closest to the Earth: 1988 October 22 (1.8047 AU) Calculated path: CET (Disc) [Did not leave this constellation] Y.-L. Ge and Q. Wang (Beijing Observatory, Xinglong Station, China) were conducting a survey for near-Earth asteroids with a 60-cm Schmidt telescope. While stereoscopically examining plates, they compared a 15-minute exposure obtained on 1988 November 4.60 and an eight-minute exposure obtained on November 4.64, and found “a slowly moving, faint and fuzzy image with an estimated magnitude 16.” They preliminarily accepted it as a faint comet. The object’s position on the first plate was α = 2h 53.5m, δ = +3
580 (2000). As soon as the report reached the Central Bureau for Astronomical Telegrams (Cambridge, Massachusetts, USA), notices were dispatched to other observatories for confirmation. Almost immediately, C. S. Shoemaker and E. M. Shoemaker (Palomar Observatory, California, USA) reported prediscovery images on film exposed for the Palomar Asteroid and Comet Survey on October 11.48, October 11.52, and November 4.37, using the 46-cm Schmidt telescope. They estimated the magnitude as 16.5 in October and 16 in November, while the comet was always diffuse, with a strong condensation, but no tail. At the end of November, T. Kojima (Chiyoda, Gunma, Japan) found prediscovery images on photographs exposed with his 25-cm reflector on November 3.54 and November 3.58. He estimated the magnitude as 17. The comet had reached a maximum elongation of 168
on November 3. R. H. McNaught (Siding Spring Observatory, New South Wales, Australia) photographed the comet using the 51-cm Uppsala Southern Schmidt telescope on November 19 and estimated the magnitude as 17. T. Seki (Geisei, Kochi, Japan) photographed the comet using his 60-cm reflector on November 28 and 30. The magnitude on the first date was 16.9–17.0, while it was 17.1 on the second date. The comet was last detected on December 7.11 and December 13.11, when C.-Y. Shao (Oak Ridge Observatory, Massachusetts, USA) obtained exposures of 30 and 35 minutes, respectively, using the 155-cm reflector. The comet appeared faint on the first photograph, due to a poor sky. He did find a weak image close to a bright star on the second photograph and gave 377

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the position as α = 2h 37.2m, δ = +2
190 (2000). The comet had attained its most southerly declination of +2.3
on December 8. The first orbit was calculated by B. G. Marsden and was published on 1988 November 19. He used five positions from October 11 and November 4, and determined the perihelion date as 1988 June 22.77 and the period as 9.91 years. Marsden wrote, “The poor distribution of observations introduces substantial uncertainty, but a parabolic solution seems out of the question.” Marsden revised his calculations on November 29, using a total of eight positions from October 11 to November 19. He determined the perihelion date as 1988 May 23.71 and the period as 11.39 years. Another revision was published by Marsden on December 23, which used 11 positions from October 11 to December 7. The result was a perihelion date of May 23.77 and a period of 11.37 years. Orbits using positions spanning the entire period of visibility were calculated by S. Nakano (1989), and Ge, Wang, and T. Han (1990). Nakano determined the perihelion date as May 23.84 and the period as 11.34 years. Ge, Wang, and Han determined the perihelion date as May 23.88 and the period as 11.37 years. Multiple apparition orbits have been calculated by K. Kinoshita (1999, 2010), Marsden (2001), and Nakano (2005, 2010). The calculations included full planetary perturbations, while those published in 2010 also solved for nongravitational effects. The perihelion date was given as May 23.97–24.00 and the period was 11.33 years. The nongravitational terms were given as A1 = +8.50 and A2 = 0.3892 by Kinoshita (2010) and Y1 = +1.447 and Y2 = 0.01989 by Nakano (2010). The orbit of Nakano (2005) is given below. T ω Ω (2000.0) i q e 1988 May 23.9826 (TT) 176.1674 180.5370 11.6666 2.518520 0.500649

absolute magnitude: H10 = 10.9 (Meyer) full moon: Sep. 25, Oct. 25, Nov. 23, Dec. 23 sources: C.-Y. Shao, HOPL (1988); Y.-I. Ge, Q. Wang, C. S. Shoemaker, E. M. Shoemaker, and B. G. Marsden, IAUC, No. 4677 (1988 Nov. 19); T. Kojima, R. H. McNaught, and B. G. Marsden, IAUC, No. 4681 (1988 Nov. 29); C. S. Shoemaker, E. M. Shoemaker, T. Kojima, Y.-L. Ge, Q. Wang, R. H. McNaught, T. Seki, C.-Y. Shao, and B. G. Marsden, MPC, Nos. 13927, 13996 (1988 Dec. 23); T. Seki and C.-Y. Shao, MPC, No. 14084 (1989 Feb. 20); S. Nakano, CCO, 6th ed. (1989), pp. 32, 64; S. Nakano, Nakano Note, No. 533 (1989 May 15); Y.-L. Ge, Q. Wang, and T. Han, CAA, 14 (1990 Mar.), pp. 112–15; K. Kinoshita correspondence with G. W. Kronk (1999, 2010); T. Seki, MPC, No. 36620 (1999 Nov. 23); B. G. Marsden, CCO, 14th ed. (2001), pp. 98–9; S. Nakano, Nakano Note, No. 1151 (2005 Jan. 19); S. Nakano, Nakano Note, No. 1999 (2010 Oct. 13).

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C/1988 W1 Discovered: 1988 November 18.18 (Δ = 0.96 AU, r = 0.03 AU, Elong. = 0.7
) (SMM 6) Last seen: 1988 November 18.26 (Δ = 0.97 AU, r = 0.02 AU, Elong. = 0.5
) Closest to the Earth: 1988 December 17 (0.7451 AU) 1988 XXII=1988p Calculated path: LIB (Disc), [Did not leave this constellation] O. C. St. Cyr (NASA Goddard Space Flight Center, Greenbelt, Maryland, USA) discovered this comet during a routine inspection of coronagraph/ polarimeter images obtained by the Solar Maximum Mission (SMM). The first image was obtained on 1988 November 18.18 and the comet was estimated as magnitude 1. The position was α = 15h 36.0m, δ = 20
030 (2000). Additional images were obtained on November 18.25 and November 18.26, with the position on the latter date given as α = 15h 37.5m, δ = 19
450 (2000). The comet vanished in a coronal streamer and was not seen again. B. G. Marsden (1988) said the positions could be represented by the orbit given for comet SMM 5, but with the perihelion date adjusted to 1988 November 18.35. An even better fit could be obtained if the perihelion date was given as November 18.36 and the perihelion distance changed from 0.0053 AU to 0.0056 AU. An orbit with a perihelion date of November 18.37 was calculated by Marsden (1989) and this is given below. T 1988 Nov. 18.369 (TT)

ω 91.084

Ω (2000.0) 14.021

i 144.796

q 0.00590

e 1.0

sources: O. C. St. Cyr and B. G. Marsden, IAUC, No. 4684 (1988 Dec. 3); B. G. Marsden, AJ, 98 (1989 Dec.), pp. 2308–9. C/1988 Y1 Discovered: 1988 December 29.84 (Δ = 0.60 AU, r = 0.63 AU, Elong. = 38
) (Yanaka) Last seen: 1989 February 27.49 (Δ = 0.97 AU, r = 1.70 AU, Elong. = 120
) Closest to the Earth: 1989 January 21 (0.3311 AU) 1988 Calculated path: OPH (Disc), SER (1989 Jan. 1), OPH (Jan. 3), LIB (Jan. 5), XXIV=1988r HYA (Jan. 16), CEN (Jan. 18), VEL (Jan. 28), PUP (Feb. 10) T. Yanaka (Motegi, Tochigi, Japan) discovered this comet on 1988 December 29.84, using 25  150 binoculars. He verified the object using a 40-cm reflector and gave the position as α = 16h 38.0m, δ = +1
020 (2000). Yanaka described the comet as diffuse, about 30 across, with condensation. He estimated the magnitude as 9–9.5. Yanaka noted that the comet was probably moving toward the northwest. A confirmation came from D. H. Levy (Tucson, Arizona, USA), who saw the comet on December 30.55, in bright moonlight, using his 41-cm reflector. He reported the comet was actually southwest of Yanaka’s discovery position. Levy gave the magnitude as 8.6, noting a moderately condensed coma 20 across and a tail extending 70 in PA 290
.

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The only other observations made in December were reported by G. W. Kronk (Troy, Illinois, USA) and A. Hale (Las Cruces, New Mexico, USA), both of whom saw the comet in moonlight. Kronk was using his 33-cm reflector under very clear skies. He determined the magnitude as 9.1, said the coma was 2.30 across, and noted a “slight extension” toward the west. Hale saw the comet with his 41-cm reflector and gave the magnitude as 9.4. He reported a moderately condensed coma 1.50 across and said a tail extended at least 30 in PA 295
. Hale added, “the tail might be about twice as long as reported; this tail was sharp along its northern edge and diffuse along its southern edge.” The comet faded during January and was fairly well observed until moonlight began interfering for several nights after the 19th. The two most prolific observers were A. Nakamura (Kuma, Ehime, Japan) and Kronk, each of whom saw the comet on six nights. Nakamura was using his 20-cm reflector and reported the comet faded from 8.8 to 9.3 from the 3rd to the 17th. His observations indicated that the coma remained moderately condensed and generally increased in diameter from 3.00 to 4.50 , while a tail extended toward PA 310
on the 4th and 5th. Kronk continued using his 33-cm reflector and indicated that the magnitude faded from 9.3 to about 10.3 from the 4th to the 19th. He reported the coma was strongly condensed on the 4th and 10th, while the diameter varied from 1.90 to 2.80 . Kronk added that the tail extended 70 in PA 300
on the 4th and 40 in PA 281
on the 10th. Hale saw the comet on three nights spanning the 5th to the 15th. He said the magnitude faded from about 9.8 to 10.1. On the 5th, Hale noted “some tail material was observed towards the [west] – this was again sharp along its northern edge.” For the 10th, Hale noted a “faint, amorphous outer coma seen; some tail material was again observed towards the west – again, this was sharp along its northern edge.” Following interference from moonlight, A. C. Gilmore and P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) exposed two photographs on the 29th using a 61-cm reflector. They estimated the magnitude as 12. The comet attained its most southerly declination of 44
on January 30. This comet was last detected during February. Hale made the last visual observation on the 3rd, when his 41-cm reflector revealed a magnitude of 12.5. Photographs by Gilmore and Kilmartin revealed the nuclear magnitude as 16.3 on the 8th, 16.0 on the 13th, and 16.6 on the 14th. The comet reached a maximum elongation of 125
on February 12. T. Seki (Geisei, Kochi, Japan) photographed the comet using his 60-cm reflector on the 26th. He gave the magnitude as 16.8. The comet was last detected on February 27.49, when M. Tsumura (Oishi, Wakayama, Japan) photographed it using a 31-cm reflector. He estimated the magnitude as 15.5. The position was α = 7h 30.4m, δ = 29
490 (2000). The first parabolic orbit was calculated by B. G. Marsden and was published on 1989 January 4. This used eight positions from January 1–3 and gave the perihelion date as 1988 December 11.76. 380

cometography: a catalog of comets

Additional parabolic orbits were published by Marsden on January 8, January 26, and March 22. All of these orbits basically produced a perihelion date of December 11.65. The last orbit only used positions through January 29 and no further orbits were published for the next few decades. For this volume of Cometography, G. W. Kronk calculated an orbit using positions spanning the entire apparition. He used 36 positions from January 1 to February 27 and included full planetary perturbations. This revealed a hyperbolic orbit with a perihelion date of December 11.66 and an eccentricity of 1.00019. This orbit is given below. T ω Ω (2000.0) i q e 1988 Dec. 11.6569 (TT) 88.1306 315.5275 71.0239 0.427835 1.000187

absolute magnitude: H0 = 12.6, n = 4.8, from visual observations (Meyer) full moon: Dec. 23, 1989 Jan. 21, Feb. 20, Mar. 22 sources: T. Yanaka and D. H. Levy, IAUC, No. 4696 (1988 Dec. 30); A. Hale, ICQ, 11 (1989 Jan.), pp. 9, 19–20; A. Hale, IAUC, No. 4697 (1989 Jan. 3); B. G. Marsden, IAUC, No. 4699 (1989 Jan. 4); B. G. Marsden, IAUC, No. 4706 (1989 Jan. 8); G. W. Kronk and A. Hale, IAUC, No. 4708 (1989 Jan. 8); A. Hale, G. W. Kronk, and B. G. Marsden, IAUC, No. 4723 (1989 Jan. 26); A. C. Gilmore, P. M. Kilmartin, and B. G. Marsden, MPC, Nos. 14233, 14322 (1989 Mar. 22); A. Hale, ICQ, 11 (1989 Apr.), p. 33; A. C. Gilmore, P. M. Kilmartin, and T. Seki, MPC, No. 14521 (1989 May 20); M. Tsumura, MPC, No. 16123 (1990 Apr. 10); A. Nakamura, ICQ, 12 (1990 Jul.), pp. 86–7; D. H. Levy, ICQ, 13 (1991 Jul.), p. 114; G. W. Kronk, ICQ, 15 (1993 Jan.), p. 17. 107P/Wilson– Recovered: 1988 December 20.52 (Δ = 1.92 AU, r = 2.57 AU, Elong. = 121
) Harrington Last seen: 1989 February 6.58 (Δ = 1.90 AU, r = 2.88 AU, Elong. = 176
) Closest to the Earth: 1988 April 25 (1.8330 AU), 1989 January 17 (1.8331 AU) Calculated path: Leo (Rec), CNC (1989 Jan. 28) This apparition officially marked the recovery of minor planet 1979 VA, at which time it received the formal minor planet designation of 4015. It would be another three years before this object was linked to comet Wilson–Harrington, which had been detected on only four nights during November 1949. B. G. Marsden (1988) took 50 positions from the 1979 apparition and determined a new orbit. He integrated it to this apparition, using perturbations by all nine planets, and predicted the next perihelion date as 1988 May 7. He provided an ephemeris covering the period of 1988 December 5 to 1989 March 15. J. B. Gibson (Palomar Observatory, California, USA) recovered this object on 1988 December 20.52, using the 152-cm reflector and a CCD camera. 381

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He estimated the magnitude as 20.5 and gave the position as α = 9h 56.4m, δ = +10
080 (2000). Gibson also obtained two images during December 20.53–20.54, as well as three images during December 24.44–24.57. The only other observations obtained during this apparition were made by observers at Siding Spring Observatory (New South Wales, Australia) on 1989 February 6.53 and February 6.58, with the position determined as α = 9h 10.7m, δ = +13
060 (2000) on the latter date. The magnitude was estimated as 20. Each observation revealed the object as stellar in appearance. The comet reached a maximum elongation of 177
on February 5. Multiple apparition orbits have been calculated by B. G. Marsden (1989), S. Nakano (1998, 2002, 2006), and K. Kinoshita (2003). These calculations included full planetary perturbations. The result was a perihelion date of 1988 May 7.92 and a period of 4.29 years. The orbit of Nakano (2006) is given below. T ω Ω (2000.0) i q e 1988 May 7.9229 (TT) 90.9419 271.0642 2.7857 0.996252 0.622833

absolute magnitude: H10 = 14.5 (Meyer) full moon: Nov. 23, Dec. 23, 1989 Jan. 21, Feb. 20 sources: B. G. Marsden, MPC, Nos. 14014, 14032 (1988 Dec. 23); J. B. Gibson, [Siding Spring], and B. G. Marsden, MPC, Nos. 14273, 14288, 14329 (1989 Mar. 22); S. Nakano, Nakano Note, No. 672 (1998 Apr. 29); S. Nakano, Nakano Note, No. 848 (2002 May 7); K. Kinoshita correspondence with G. W. Kronk (2003); S. Nakano, Nakano Note, No. 1326 (2006 Apr. 12). 29P/ Recovered: Visible throughout orbit Schwassmann– Last seen: Visible throughout orbit Wachmann 1 Closest to the Earth: 1989 September 21 (4.7771 AU) Calculated path: LEO (Aphelion), VIR (Jul. 13), CRT (Aug. 12), VIR (Aug. 18), 1989 XV CRV (Oct. 20), VIR (Nov. 16), CRV (1983 May 3), VIR (Jul. 23), HYA (Nov. 27), LIB (Nov. 30), HYA (1984 Jan. 4), LIB (Jul. 3), HYA (Sep. 15), LIB (Oct. 6), SCO (Nov. 30), OPH (1985 Oct. 29), SGR (Dec. 27), CAP (1987 Feb. 24), SGR (Sep. 18), CAP (Oct. 9), AQR (1988 Feb. 14), CAP (Feb. 17), AQR (Mar. 31), CAP (Sep. 25), AQR (Nov. 20), PSC (1989 Feb. 23), PEG (Aug. 30), PSC (Sep. 4), ARI (1990 Jul. 21), PSC (Sep. 11), ARI (1991 Mar. 9), TAU (Jul. 19), ARI (Nov. 15), TAU (1992 Mar. 16), AUR (Jun. 24), GEM (1993 Jun. 30), CNC (1994 Jun. 30), LEO (Nov. 1), CNC (1995 Jan. 1), LEO (Jul. 5), SEX (Oct. 20), LEO (Dec. 17), SEX (Dec. 31), LEO (1996 Aug. 4), VIR (Oct. 13) This comet passed aphelion on 1982 May 7 and in the course of this apparition it would move between declinations of 32
(1985 May 3) and +32
(1992 November 23). Although the comet continued to undergo strong outbursts in brightness, this apparition was unusual in that the comet rarely 382

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seemed to cease activity, as it did in the past. D. C. Jewitt (1989, 1990) was the first to notice this constant activity and suggested, “It is likely that SW1 is active all around its present orbit.” The comet was moved into its present orbit during the previous apparition. At the time of the comet’s perihelion in 1974, its orbit was already being strongly affected by Jupiter, with its closest distance from the giant planet coming on 1974 May 21 (1.0028 AU). This close approach ultimately reduced the comet’s period from 16.10 years to 14.85 years. Although the perihelion distance was increased from 5.54 AU to 5.77 AU, the aphelion distance was decreased from 7.26 AU to 6.33 AU, as the orbit became more circular. The comet had undergone an outburst prior to passing aphelion in 1982, becoming brighter than magnitude 12 during April; however, J. E. Bortle (Stormville, New York, USA) could not find it on May 12, using his 32-cm reflector, and concluded it was fainter than 13.0. The comet was photographed by A. B. Bijaoui and R. Chemin (Côte d’Azur Observatory, Caussols, France), using the 90-cm Schmidt telescope on May 19.87 and May 24.91, which proved to be the final observations of 1982. They gave the position on the first photograph as α = 11h 24.5m, δ = 4
330 (2000). Although a few amateur astronomers attempted both visual and photographic observations, none were successful. They generally concluded that the comet was fainter than magnitude 12–13. The comet reached a minimum elongation of 7
on October 3. Several visual observations were acquired during outbursts in 1983. Pearce failed to see the comet with his 15-cm reflector on January 9 and 12, estimating that it was probably fainter than magnitude 12.0. Merlin observed the comet on February 19 and 20, giving the magnitude as 12.0 and 11.9, respectively. He noted a slightly condensed coma that was 1.60 across on the 19th and 1.70 across on the 20th. J. D. Shanklin (Cambridge, England) saw the comet with a 20-cm refractor on the 23rd, judging the magnitude as 12.1. He said the coma was moderately condensed and 1.10 across. Merlin photographed the comet using his 26-cm reflector on March 6 and estimated the magnitude as 12.5. He noted a slightly condensed coma about 10 across. Both Pearce and Merlin attempted to see the comet on several nights from March 13 to April 17, but were not successful. T. Seki (Geisei, Kochi, Japan) did manage to photograph the comet on April 5 and estimated the magnitude as 18. Merlin visually spotted the comet on April 29. He gave the magnitude as 11.7 and said the moderately condensed coma was 1.50 across. Merlin noted an extension toward PA 239
. Pearce saw the comet during May 6–9, noting the magnitude brightened from 12.1 to 11.9, while the coma expanded from 1.40 to 2.20 . The coma showed little or no condensation. Astronomers at Siding Spring Observatory (New South Wales, Australia) photographed the comet on May 12 and estimated the magnitude as 14. On that same night, Shanklin was unable to see the comet and estimated that it was fainter than magnitude 11.9. Merlin (Pic du Midi 383

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Observatory, France) photographed the comet using a 60-cm reflector on July 12 and 13. He gave the magnitude as 13.5 and 14.0, respectively, noting a slightly condensed coma 10 across. During this year, the comet reached a maximum elongation of 170
on April 12 and a minimum elongation of 8
on October 28. The comet was only observed by astronomers at Perth Observatory (Bickley, Western Australia, Australia) in 1984. P. Jekabsons photographed it on May 3, while M. Candy and V. Candy photographed it on June 19. No physical descriptions were provided. Pearce made several attempts to see the comet from January 11 to July 27, but was unsuccessful. He generally estimated that the comet must have been fainter than magnitude 12.0. Photographs by Merlin on April 23 and June 16 also failed to show the comet and he estimated it was probably fainter than magnitude 13.5–14.0. The comet reached a maximum elongation of 169
on May 6 and a minimum elongation of 8
on November 20. Several visual observers reported unsuccessful observations of this comet during 1985. For the most part this indicated the comet never became brighter than magnitude 12.5 during the period of February 23 to July 26. On the other hand, successful photographic observations using the 33-cm astrograph were reported by astronomers at Perth Observatory. They reported precise positions for May 13, May 17, May 24, June 19, and July 22; however, no descriptive information was provided. The comet reached a maximum elongation of 170
on June 1 and a minimum elongation of 6
on December 16. During 1986, the comet was observed from March 22 to November 20, with the comet reaching its maximum elongation on June 29 (173
). Merlin and V. F. de Assis Neto (Sao Francisco de Oliveira, Brazil) made the only visual observations of the comet in early April. The comet was then undergoing an outburst. Merlin was visiting de Assis Neto and saw the comet using a 31-cm reflector. They judged the magnitude as 12.0 on both the 4th and 5th, and 12.7 on the 7th. Merlin provided several descriptions. On the 4th, he described the comet as “a round and diffuse 0.90 patch with a 2000 central condensation.” On the 5th, Merlin said the coma was 1.00 across and noted “the comet’s central region was slightly more condensed.” He also saw, “a spiral streamer starting at the [west] edge of the central condensation and then curving to the [north].” Merlin said the outburst was declining on the 7th, with the comet simply appearing as “a faint, diffuse, rather uniform patch” 0.80 across. Observations were reported by four observatories. Prior to the observations reported above, W. Wisniewski (Cerro Tololo Inter-American Observatory, Chile) had acquired CCD images on March 16 and March 17, which put the B magnitude at 18.4. T. Gehrels (Steward Observatory, Kitt Peak, Arizona, USA) acquired CCD images of the comet on April 15, using the 91-cm reflector, and simply noted the comet was “considerably fainter” than when seen by Merlin and de Assis Neto. K. J. Meech and D. C. Jewitt (Cerro Tololo) used the 61-cm 384

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Schmidt telescope to obtain 40-minute exposures on May 5 and May 7, while Meech (Kitt Peak National Observatory, Arizona, USA) used the 213-cm reflector to acquire a single CCD image on June 3 and three CCD images on June 4. No physical descriptions were provided. During 1987, the comet was observed from April 24 to November 9, with the comet reaching its minimum elongation on January 11 (3
) and its maximum elongation on July 27 (178
). T. Kojima (Chiyoda, Gunma, Japan) photographed the comet on April 24 and April 29, using a 25-cm reflector, estimating the magnitude as 15 and 14, respectively. On May 3, Gehrels and J. V. Scotti obtained CCD images using the 91-cm reflector, judging the magnitude as 14.7. They said the comet exhibited a strong nuclear condensation within a coma measuring 2.00 by 1.70 . There was also a jet-like structure, mostly toward PA 150
. The first visual observations of the year were made during May, when Pearce (Broome, Western Australia, Australia) and M. L. Clark (Western Australia, Australia) saw the comet with their 20-cm reflectors from the 6th to the 9th. Pearce said the comet brightened from 12.1 to 11.9, displaying a very slight condensation. He added that the coma diameter increased from 1.40 to 2.20 . Clark gave the magnitude as 12.0 on each night, noting very slight condensation in a coma. He added that the coma diameter increased from 20 to 30 . On June 22, D. H. Levy (Catalina Station, Mt. Bigelow, Arizona, USA) saw the comet with the 154-cm reflector and estimated the magnitude as 14.0. He added that the coma was very slightly condensed. Several observers made attempts to observe the comet from July through September, but were unsuccessful. Another outburst allowed another series of visual observations in October. A. Hale (Las Cruces, New Mexico, USA) saw the comet on the 16th and 17th, using his 41-cm reflector, and gave the magnitude as 13.2 and 13.3, respectively. He added that the comet was very slightly condensed on the second night. Hale said the comet’s “appearance suggests outburst is ~1 week old.” C. S. Morris (California, USA) saw the comet with his 26-cm reflector on the 18th. He gave the magnitude as 13.3 and said the coma was very slightly condensed and 1.60 across. E. A. Jacobson (Minnesota, USA) saw the comet on the 21st while using his 25-cm reflector. He estimated the magnitude as 13 and said the coma was totally diffuse. On October 23, R. A. Keen (Mt. Thorodin, Colorado, USA) saw the comet with his 32-cm reflector and gave the magnitude as 13.0. He said the coma was uncondensed and 1.50 across. Visual observations were attempted by several observers during the remainder of October and into December, but the comet was apparently fainter than magnitude 13.0. Although several observatories photographed the comet during the year, none provided physical descriptions. During 1988, the comet was observed from April 15 to December 30, with the comet reaching its minimum elongation on February 6 (1
) and its maximum elongation on August 24 (176
). Meech (Mauna Kea, Hawaii, USA) made the first observation of the year on April 15 using a 224-cm reflector. Her two CCD images revealed an estimated magnitude of 17. 385

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Meech also acquired CCD images with the same telescope on May 18 and 19, but did not provide physical descriptions. J. B. Gibson (Palomar Observatory, California, USA) acquired a CCD image of the comet on May 27 using the 152-cm reflector and a Gunn R filter. He determined the magnitude as 14.4. He also noted the coma was 2500 across, while a tail extended 1000 in PA 190
. Another image was obtained by Gibson on June 21. This revealed a magnitude of 14.6, a nuclear magnitude of 17.1, and a coma diameter of about 1500 . M. Jäger (Fischamend, Austria) photographed the comet on July 27 using a 20-cm reflector. The magnitude was estimated as 13, while the diffuse, centrally condensed coma was 20 across. Visually, observations had been attempted by several observers since late May, but all were unsuccessful until August 12, when D. A. J. Seargent (The Entrance, New South Wales, Australia) saw the comet with his 25-cm reflector. The magnitude was given as 13.7 and the coma was described as “stellar.” On the 15th, Hale gave the magnitude as 13.6 and said, “comet apparently near onset of new outburst; coma small and very condensed.” Seargent gave the magnitude as 13.7 on the 16th and wrote, “no longer stellar, but very marginal.” Morris (Pine mountain Club, California, USA) judged the magnitude as 12.8 on the 20th, noting a slightly condensed coma 1.10 across. He wrote, “hint of spiral structure, coma was asymmetric.” On the 21st, Morris reported a magnitude of 12.8 and said the coma was 1.60 across. Hale indicated the comet brightened from magnitude 13.4 to 12.9 during August 21 to September 7, noting the coma was 20 across on the last night. Morris determined the magnitude as 12.8 on September 10 and 11, reporting a slightly condensed coma 1.90 across. Scotti and Levy (Tucson, Arizona, USA) were observing with a 40-cm reflector on the 17th and judged the magnitude as 13.3 and 13.4, respectively. Levy said the coma was slightly condensed and 0.50 across. Levy reported a magnitude of 13.6 on the 18th and 13.3 on the 20th. Several observers reported unsuccessful attempts to see the comet during the next few weeks, but Morris managed to spot it at magnitude 13.4 on October 31. He added that it appeared very slightly condensed and 1.50 across. Although a photograph by Kojima on December 1 failed to reveal the comet, prompting him to estimate that it was fainter than magnitude 16, his photographs of December 5, 7, 10, and 30 revealed the comet at magnitude 14. Photographs by T. Nakamura and J. Souchay (Kiso Observatory, Nagano, Japan) on December 6 and 7 revealed magnitudes of 14.5 and 14.8, respectively. They noted a strongly condensed coma on the first night that was 0.30 across, but said the condensation was fainter on the second night. Also on the 7th, CCD images were acquired by J. Watanabe, K. Takagishi, G. Minagi, H. Sugino, and T. Kuroki (Kagoshima Space Center, Kimotsuki, Kagoshima, Japan) using a 60-cm reflector. They gave the magnitude as 14.6 and said the coma measured 0.30 along the north–south axis and 0.40 in PA 100
to PA 280
. During 1989, the comet was observed during the first few days of January and then from June 2 to December 31, with the comet reaching 386

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its minimum elongation on March 5 (4
) and its maximum elongation on September 22 (172
). Kojima photographed the comet on January 1 and 2, estimating the magnitude as 14. Hale then spotted the comet on January 9 and 10, giving the magnitude as 13.2 and 13.3, respectively. The comet was at a low altitude on both nights. Hale noted that the comet’s appearance on the first night suggested an outburst that was about one week old. Meech acquired images of the comet on June 2 and 3, but provided no physical descriptions. Photographs by Kojima on July 6 indicated a magnitude of 14. He described the comet as diffuse with a strong condensation. R. Lunsford (Chula Vista, California, USA) saw the comet on the 8th using his 41-cm reflector. He determined the magnitude as 11.7 and said the coma was 30 across. Hale gave the magnitude as 12.6 and 12.7 on the 9th and 11th, respectively, describing the comet as “quite diffuse.” Morris judged the magnitude as 13.1 on the 10th. He added that the coma was slightly condensed and 1.00 across. Morris next saw the comet on July 29, 30, and 31. He said the magnitude was 13.5 on the first two nights and 13.4 on the last night. The coma was slightly diffuse during this time and expanded from 1.00 to 1.40 . Hale next spotted the comet on August 3 and estimated the magnitude as 13.1. He described the comet as “vague, diffuse and large.” Morris’ observations on the 5th and 6th indicated magnitudes of 13.2 and 13.3, respectively. He described the coma as very slightly condensed, with a diameter of 1.90 on the first night and 1.50 on the second night. Morris suspected the comet on the 12th, estimating the magnitude as 13.2, and noted it was a difficult observation as the comet was near a “relatively bright star.” He again suspected the comet at magnitude 13.4 on the 13th and 27th. M. Tsumura (Oishi, Wakayama, Japan) photographed the comet on August 28 and estimated the magnitude as 14. He said the comet was slightly condensed and 1.50 across. On September 3, Tsumura estimated the photographic magnitude as 15, while S. Korth (Düsseldorf, Germany) estimated the magnitude as 14.0. Korth was using a 36-cm reflector and added that the coma was moderately condensed and 0.20 across. Astronomers at the Bulgarian National Observatory (Rozhen, Bulgaria) found an asteroidal object on a plate exposed with the 50-cm Schmidt telescope on September 3 in bad seeing. It received the minor planet designation “1989 RL5.” Nakano (1991) identified this “minor planet” as comet 29P. Photographs by Tsumura revealed magnitudes of about 14.5 on the 9th, 15 on the 11th and 13.0 on the 20th. The comet was undergoing another outburst in the latter image, as he noted it was stellar. Hale gave the magnitude as 12.8 on the 23rd, 12.5 on the 25th, and 12.5 on the 30th. The comet was observed by a large number of observers throughout the month of October, except around mid-month when moonlight interfered. Hale gave the magnitude as 12.2 on the 3rd. Morris provided magnitudes of 12.1 and 12.3 on the 7th and 8th, respectively. He also said the coma diameter decreased from 1.8’ to 1.40 during this time. Hale judged the magnitude as 12.6 on the 8th. Keen gave the magnitude as 13.6 on the 387

cometography: a catalog of comets

20th and 12.3 on the 23rd, while Morris gave the magnitude as 13.3 on the 28th and 12.8 on the 30th. Morris described the comet as very slightly condensed with a diameter that expanded from 0.80 to 1.30 . The comet became more difficult to see during the remainder of the year. Hale obtained the last visual observation on November 4. He estimated the magnitude as 13.0 and said the coma was uncondensed. Tsumura obtained a few more photographs, estimating the magnitude as 15.5 on November 24, 16 on November 26, and 13.5 on December 21. Only one observation of the comet was made during the early months of 1990, as the comet’s elongation was decreasing. Tsumura photographed the comet on January 17 and estimated the magnitude as 14.5. He added that the coma was very slightly condensed and 1.20 across. The comet passed 7
from the Sun on April 3. The comet was well observed during the latter half of 1990, reaching a maximum elongation of 169
on October 22. Tsumura made the first observation when he photographed the comet on July 30. This revealed a magnitude of about 13.0 and a moderately condensed coma 0.50 across. R. J. Bouma (Netherlands) visually spotted the comet with his 25-cm reflector on August 3. He judged the magnitude as 13.1 and said the moderately condensed coma was 0.30 across. No further visual observations were made during the next few weeks as the comet faded. E. Konno (Japan) did photograph the comet with a 16-cm reflector during the latter half of August, noting magnitudes of about 14.5 on the 18th, 15 on the 20th, 16 on the 22nd, and 15.5 on both the 23rd and 25th. Bouma managed another visual observation on the 26th, this time using a 106-cm reflector at Puimichel (France). He gave the magnitude as 13.7 and said the coma was uncondensed and 1.20 across. Another photograph by Konno on August 27 revealed a magnitude of about 14.5 and a slightly condensed coma 0.80 across. Following a period of moonlight in early September, Hale spotted the comet on the 12th and 13th, providing magnitudes of 12.8 and 12.7, respectively. Morris saw the comet on the 15th and gave the magnitude as 12.4. He added that the coma was 2.10 across and exhibited no stellar condensation. Morris used a 51-cm reflector to observe the comet on the 16th. He determined the magnitude as 12.0 and the coma diameter as 1.90 . On the 20th, Keen gave the magnitude as 12.1 and noted an uncondensed coma 20 across. Hale gave the magnitude as 12.6 on the 25th. The comet was seen by Pearce on September 27 and 28, and was described as very slightly condensed. He judged the magnitude as 13.0 and the coma diameter as 10 on the first night and 13.2 and 1.30 on the second night. R. J. Modic (Ohio, USA) observed the comet with his 40-cm reflector on October 1. He gave the magnitude as 12.8, adding that the coma was very slightly condensed and 1.70 across. Another observation was made by Modic on the 2nd, when he “strongly suspected” the comet, giving the magnitude as 13.2 and the coma diameter as 1.20 . Photographs by Konno on the 10th and 11th showed the comet at about magnitude 16, with a coma 10 across. Morris 388

cometography: a catalog of comets

again observed the comet with a 51-cm reflector on the 14th. He gave the magnitude as 13.5 and said the coma was uncondensed and 1.00 across. Tsumura photographed the comet on the 21st and 28th, estimating the magnitude as 15 and 14.5, respectively. He added that the coma was slightly condensed and 0.50 across on both nights. Morris made several observations during November. He determined the magnitude as 12.0 and 12.5 on the 10th and 11th. The coma was uncondensed, with a diameter of 2.30 and 1.80 , respectively. During the 22nd to the 25th, Morris said the comet faded from 12.6 to 12.9. The coma was very slightly condensed and 1.7–1.80 across. Photographs were also obtained by Tsumura in November. He estimated the magnitude as 13.0 on the 12th and said a tail extended 0.60 in PA 230
. Tsumura estimated the magnitude as 13.5 on the 17th and reported a tail extending 0.60 in PA 195
. Konno and Tsumura photographed the comet in December. Konno estimated the magnitude as 15 on the 4th and 5th. Tsumura estimated the magnitude as 14.5 on the 6th, noting a moderately condensed coma 0.50 across. Konno estimated the magnitude as 13.5 on the 13th and said the tail extended 1.20 in PA 35
. Tsumura estimated the magnitude as 15 on the 21st, noting a slightly condensed coma 0.30 across. During 1991, only four observations were made during January and February, while the comet was well observed during August to December. The comet reached its minimum elongation on May 3 (8
) and its maximum elongation on November 19 (169
). Although several visual observations were attempted during January to March, none were successful, leading observers to estimate that the comet was fainter than magnitude 13. Tsumura photographed the comet on January 6 and estimated the magnitude as 16. He also noted a slightly condensed coma 0.30 across. Konno photographed the comet on February 3 and estimated the magnitude as 15. He said the coma was 0.8’ across. Astronomers at Oak Ridge Observatory (Massachusetts, USA) acquired images of the comet on February 9 and 16, using the 155-cm reflector and a CCD camera, but no descriptive information was provided. Several observers tried to visually see the comet during July, but none were successful. They indicated that the comet must have been fainter than magnitude 14 around mid-month. The comet apparently experienced another outburst in early August, with Modic finding it on the 7th with his 20-cm reflector. He gave the magnitude as 12.0 and noted a slightly condensed coma 3900 across. Using this telescope, as well as others with a 36-cm and 40-cm aperture, Modic remained the most prolific observer during the remainder of August. He judged the magnitude as 12.6 on the 8th, 12.0 on the 11th, 12.5 on the 13th, 12.2 on the 14th, 12.5 on the 19th, 12.5 on the 22nd, and 13.3 on the 23rd. He generally noted that the coma exhibited little condensation and increased in diameter to about 1.60 by the 22nd. Modic’s observation on the 23rd revealed only a 0.80 coma, but moonlight was then interfering. The comet had faded by September. Tsumura estimated the photographic magnitude as 12 on the 6th. 389

cometography: a catalog of comets

Modic said the magnitude was 14.2 on the 7th, while the coma was very slightly condensed and 1.00 across. A photograph by Konno on the 9th revealed a magnitude of about 14.5 and a very slightly condensed coma 2.50 across. A visual observation by H. Mikuz (Ljubljana, Slovenia) was made on the 11th, using a 36-cm reflector. He estimated the magnitude as 14.0 and said the coma was about 30 across. V. L. Korneev (Zelenograd, Russia) gave the magnitude as 12.9 on September 27 while using his 25-cm reflector. He said the coma was slightly condensed and 1.40 across. On October 3, Tsumura and Konno photographed the comet and estimated the magnitude as 13 and 15, respectively. The coma diameter was given as 50 by Tsumura and 20 by Konno. Korneev determined the magnitude as 13.3 and 13.4 on the 4th and 5th, respectively, while the coma diameter was 2.1–2.20 . Another observation by Korneev on the 7th revealed a magnitude of about 13.2 and a coma 2.50 across. Konno estimated the photographic magnitude as 14.5 on October 15 and noted a slightly condensed coma 10 across. Tsumura, Konno, and Korneev also reported a few observations in November. They indicated that the comet remained at magnitude 14 or fainter throughout the month, although Konno estimated the magnitude as 13.5 on the 29th, which indicated another outburst had occurred. The coma was generally described as moderately condensed and never exceeded a diameter of 0.80 . Tsumura estimated the photographic magnitude as 12.5 on December 2. Konno and Tsumura estimated the photographic magnitude as 12–12.5 on the 4th. The comet was visually observed from the 5th to the 13th. Hale gave the magnitude as 12.6 on the 5th and 12.7 on the 6th. Mikuz judged the magnitude as 13.7 on the 5th, 14.0 on the 9th, and 13.2 on the 11th. Hale gave the magnitude as 12.9 on the 13th. During the last half of December, Mikuz and Modic indicated the comet was fainter than magnitude 14. The comet was not well observed during 1992, with no visual observations being made until late November and early December. The comet reached its minimum elongation on May 31 (7
) and its maximum elongation on December 15 (172
). Tsumura provided the only physical descriptions for the first half of the year, as he routinely photographed the comet’s predicted position. On January 2, he estimated the magnitude as 15 and noted a slightly condensed coma 0.30 across. Tsumura indicated that the comet’s appearance was essentially unchanged on January 24. An outburst might have occurred near the end of January, as Tsumura estimated the magnitude as 12.5 and reported a very strongly condensed coma 0.20 across. He estimated the magnitude as 13 and 13.5 on the 26th and 27th. On the first night, he noted a very strongly condensed coma 200 in length, meaning they extended beyond the edge of the plate. The comet reached a minimum elongation of 19
on April 4 and passed perihelion on the 9th. Its brightness changed little in April, with no clear indication as to whether it was brightening or fading. R. W. Panther (England) saw the comet with 15  80 binoculars on 13 nights from the 468

cometography: a catalog of comets

3rd to the 30th, noting the magnitude varied from 3.9 to 5.1. Bortle saw the comet with 10  50 and 15  80 binoculars on 11 nights between the 6th and the 28th, noting magnitudes of 5.0 to 5.6. Hale saw the comet with 10  50 binoculars on several nights spanning the 2nd to the 30th and said the magnitude varied from 5.0 to 5.5. Most observers noted a strongly condensed coma throughout the month, with the coma diameter generally estimated as 1–20 across while in twilight for most of April and 3–60 across when visible in darker skies late in the month. The tail rotated from about 80–90
at the beginning of the April to about 290–300
by month’s end. A number of observers reported the tail as 3
or more in length during the last half of the April. The first naked-eye observation was made by Keen on April 21, when he judged the magnitude as 4.7. Additional naked-eye observations were reported during the remainder of the month. R. Haver (Italy) saw the comet on April 25 and 27, giving the magnitude as 4.3 and 4.4, respectively. On the 28th, M. Möller (Germany), J. V. Scotti (Kitt Peak National Observatory, Arizona, USA), and Morris independently spotted the comet, giving the magnitude as 5.0, 4.8, and 4.8, respectively. Morris added that the coma appeared very strongly condensed. Another observation by Haver on the 29th revealed a magnitude of 4.4. W. Hasubick (Germany) saw the comet on the 30th and gave the magnitude as 5.0. The comet attained its most northerly declination of +36
on April 27. The comet again seemed to show little change in brightness during May; however, the number of observations greatly increased as the comet moved further out of twilight. Checking the various issues of the International Comet Quarterly revealed that nearly 200 observers reported over 1300 observations during May. Even more impressive was that 19 observers reported a total of 47 naked-eye observations throughout the month. The magnitude estimates of some of these naked-eye observers include 4.4–5.1 by Haver from the 1st to the 30th, 4.8–5.1 by Keen from the 4th to the 30th, 4.9–5.0 by R. J. Bouma (Groningen, Netherlands) from the 2nd to the 4th, and 4.9–5.0 by Pearce from the 20th to the 24th. One thing that noticeably changed during the month was the diameter of the coma, which increased as the comet approached Earth. A total of 28 observations of the coma were reported on May 1, all of which used some optical aid. Depending on the observing instrument and sky conditions, these observations ranged from 30 to 120 , with the average being 6.70 . The comet was closest to Earth on May 25. On that night, 46 observations of the coma were reported by observers using optical aid. Again, depending on the observing instrument and sky conditions, the diameter ranged from 50 to 400 , while the average was 18.00 . The largest reported coma diameter was 600 , which was made by Bortle with the naked eye on May 27. Using the observations of experienced observers, it is obvious that the comet’s tail was at least 2
long throughout the month. Morris used 10  50 binoculars to make what is probably the finest series of tail observations. He said the tail extended 1.25
in PA 292
469

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on the 5th and 2.25
in PA 290
on the 14th. On the 20th, Morris reported four tails: an antitail extended 2
in PA 5
, while the main tails extended 3
in PA 260
, 5.5
in PA 275
, and 3
in PA 307
. On the 27th, Morris again noted four tails: an antitail extended 2
in PA 10
, while the main tails extended 0.25
in PA 125
, 1.75
in PA 280
, and 5
in PA 310
. Also on the 27th, Bortle made a naked-eye observation of the tail, noting it extended about 2
in PA 312
. M. Fulle and L. Pansecchi said conditions would be “favorable for the socalled ‘neck-line structure’” in June. In the April 10 issue of the International Astronomical Union’s Circulars, they said Earth would cross “through the plane of the comet orbit” on June 6.8. They added that the feature “should appear as a strong dust streamer within the main tail, having a short, thin, sunward spike lying inside the comet orbit with respect to the sun.” The comet faded in June, with the coma becoming more diffuse as the month progressed. The comet reached a maximum elongation of 175
on June 6. Checking the International Comet Quarterly reveals less than 200 observations were reported, quite the change from the previous month. The final naked-eye observations were made in the first week, with the magnitude being given as 5.1 by Keen on the 1st, 5.0 by K. Takamizawa (Saku, Nagano, Japan) on the 2nd, and about 6 by Camilleri on the 4th. Camilleri also saw the tail with the naked eye, noting that it extended 3.5
in PA 330
. The most prolific observers were J. G. de Souza Aguiar (Campinas, Sao Paulo, Brazil), who saw the comet with 20  50 binoculars and said it faded from magnitude 5.8 to 8.5 during the 2nd to the 18th, Camilleri, who saw the comet with 20  80 binoculars, said it faded from 6.5 to 8.5 during the 2nd to the 17th, while Morris, who used a couple of different pairs of binoculars, saw the comet fade from 5.2 to 9.1 during the 2nd to the 24th. During the same period, Morris said the coma diameter decreased from 19.50 to 7.40 . Morris saw two tails on the 2nd, one extending 3.5
in PA 329
and the other extending 0.17
in PA 110
. He also noted a tail extending 4
in PA 335
on the 3rd, 2.25
in PA 328
on the 4th, 1.25
in PA 343
on the 16th, and 1.25
in PA 350
on the 17th. Pizarro obtained a 10-minute blue exposure on June 5, which H.-H. Heyer photographically enhanced, to check for Fulle and Pansecchi’s predicted “neck-line” feature. R. M. West examined this plate and said this feature was 1.50 wide, straight, and dense, extending at least 2.6
in PA 332
. It was “within a broader, diffuse, and rather faint envelope.” West added that a “much weaker sunward spike” extended about 300 in PA 152
. The final astrometric observations of this comet were made on June 25.58, June 26.48, and June 27.62, when astronomers at Perth Observatory (Bickley, Western Australia, Australia) obtained photographs using the 33-cm astrograph. No physical descriptions were provided. The position on the last date was α = 15h 36.0m, δ = 34
490 (2000). Visual observations continued in July. Camilleri saw the comet using his 20-cm reflector on the 11th and gave the magnitude as 12.5. He said the 470

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coma was uncondensed and 10 across. Morris made the last three visual observations. Using his 26-cm reflector on the 14th and 15th, he determined the magnitude as 11.6 and 11.8 respectively. Very little condensation was noted, while the coma diameter was 1.2–1.30 . Morris last detected the comet on July 22.22 while using a 51-cm reflector. He gave the magnitude as 13.3, reporting the coma was uncondensed and 0.50 across. The comet was last detected during July 22.30–22.32, when K. J. Meech (Mauna Kea, Hawaii, USA) acquired 11 CCD images, with a total exposure time of 1380 seconds, using the 224-cm reflector and an R filter. No physical description was acquired. Another attempt to observe this comet was made by Meech (Cerro Tololo Inter-American Observatory, Chile) on 1991 May 14. She used the 402-cm reflector and an R filter to acquire 13 CCD images, totaling 1560 seconds, on the comet’s predicted position; however, no trace was found down to magnitude 24. Z. Sekanina studied the details reported about the comet’s dust tail by West on February 25–26 and Gilmore on March 2. On March 8, he wrote, “The orientation and extent of the dust tail . . . are diagnostic of submillimeter-size and larger particles released between about 900 and 500 days before perihelion, when the comet was at heliocentric distances between 10 and 7 AU.” He added, “Early tail formation of this kind is characteristic of new, Oort-cloud comets.” The earliest details of the comet’s spectrum were acquired by the International Ultraviolet Explorer (IUE) satellite. E. E. Roettger, P. D. Feldman, and M. F. A’Hearn said the satellite observed this comet on 1989 December 22 and detected the hydroxyl radical, which indicated a water production rate almost twice that of comet 1P/Halley, when at the same distance from the Sun. They added, “The dust-to-gas ratio appears to be slightly higher than that of P/Halley.” M. Wallis and A. Talavera said this satellite also observed the comet on December 29, noting the hydroxyl radical, diatomic carbon, and carbon monosulfide. They noted the hydroxyl radical was “unexpectedly strong,” translating to a water production rate “similar to P/Halley postperihelion and 50 percent higher than P/Halley preperihelion at a comparable heliocentric distance.” M. C. Festou, A’Hearn, S. A. Budzien, Feldman, and Roettger provided additional IUE results for May 7–13. They reported, “The ultraviolet spectrum is characteristic of non-dusty comets.” Additional spectra were reported as the comet became brighter. S. M. Larson (Catalina Station, Mt. Bigelow, Arizona, USA) obtained spectroscopic observations on February 25, using the 154-cm reflector and a CCD camera. He detected cyanogen, triatomic carbon, and diatomic carbon. D. J. Sahnow, Feldman, S. R. McCandliss, and M. E. Martinez (1990, 1993) obtained a long-slit far-ultraviolet spectrum from a sounding rocket experiment on 1990 April 21. During the 270 seconds of data acquisition, they detected emissions from oxygen, carbon, sulfur, and carbon monoxide. D. Bockelée-Morvan, D. Despois, G. Paubert, P. Colom, and J. Crovisier observed the comet using the Institut de Radio Astronomie Millimétrique 471

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(IRAM) 30-m telescope during May 21–25. They detected hydrogen cyanide, formaldehyde, hydrogen sulfide, and methanol. The first parabolic orbit was calculated by D. W. E. Green and was published on 1989 December 11. Green used 10 positions from December 6–11 and determined the perihelion date as 1990 April 10.30. He added that these calculations “suggest that this may become a moderately bright object in 1990 March and April.” During the next two months, Green, B. G. Marsden, and S. Nakano published additional parabolic orbits as more positions were reported. Nakano’s orbit was published on February 2 and used 19 positions reported through 1990 January 26. He determined the perihelion date as April 9.91. At the time Nakano’s orbit was published, Marsden wrote, “It certainly would seem that 1989c1 has the potential to be the best comet since 1976. On the other hand, the disappointing display of comet 1973 XII serves as a reminder that cometary brightness is notoriously unpredictable.” He added that this comet appeared to be a “new” comet from the Oort Cloud. The first hyperbolic orbit was calculated by Marsden and was published on February 27. This used 35 positions through February 19 and included full planetary perturbations. The result was a perihelion date of April 9.98 and an eccentricity of 1.00038. He indicated that the original orbit was also hyperbolic, “supporting the statement . . . that the comet is probably ‘new’ in the Oort sense.” Marsden published a revised hyperbolic orbit on March 27. This used 49 positions from 1989 December 7 to 1990 March 17 and included full planetary perturbations. The result was a perihelion date of April 9.97 and an eccentricity of 1.00030. He said both the original and future orbits were hyperbolic with eccentricities of 1.00007 and 1.00020, respectively. As positions continued to be reported, Green published revised hyperbolic orbits on April 27, May 17, and July 8. The result was a perihelion date of April 9.97 and an eccentricity of 1.00023. Nakano (1990) took 144 positions from 1989 December 6 to 1990 June 17 and included full planetary perturbations. He determined a hyperbolic orbit with a perihelion date of 1990 April 9.97 and an eccentricity of 1.00022. This orbit is given below. The 7th edition of Marsden’s Catalogue of Cometary Orbits included original and future orbits for this comet. The original orbit was elliptical with a period of about 5.5 million years, while the future orbit was hyperbolic with an eccentricity of 1.00012. T ω Ω (2000.0) i q e 1990 Apr. 9.9675 (TT) 61.5763 75.9255 58.9564 0.349775 1.000225

absolute magnitude: pre-perihelion r = 2.4 AU–1.5 AU: H0 = 4.0, n = 5; r = 1.5 AU–0.35 AU: H0 = 6.0, n = 2.2, post-perihelion: H0 = 8.5, n = 3.2 (Green, 1995)

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full moon: Nov. 13, Dec. 12, 1990 Jan. 11, Feb. 9, Mar. 11, Apr. 10, May 9, Jun. 8, Jul. 8, Aug. 6 sources: R. R. D. Austin and P. V. Birch, IAUC, No. 4919 (1989 Dec. 6); D. W. E. Green, IAUC, No. 4921 (1989 Dec. 11); D. A. J. Seargent and A. R. Pearce, IAUC, No. 4924 (1989 Dec. 18); D. W. E. Green, IAUC, No. 4926 (1989 Dec. 20); E. E. Roettger, P. D. Feldman, M. F. A’Hearn, A. R. Pearce, and D. A. J. Seargent, IAUC, No. 4934 (1989 Dec. 30); B. G. Marsden, MPC, No. 15672 (1991 Jan. 11); A. R. Pearce, IAUC, No. 4941 (1990 Jan. 12); M. Wallis and A. Talavera, IAUC, No. 4944 (1990 Jan. 16); S. Nakano, IAUC, No. 4958 (1990 Feb. 2); S. Nakano, MPC, No. 15857 (1990 Feb. 9); H.-E. Schuster, G. Pizarro, and A. Hale, IAUC, No. 4970 (1990 Feb. 26); B. G. Marsden, IAUC, No. 4972 (1990 Feb. 27); S. M. Larson, IAUC, No. 4973 (1990 Mar. 2); A. C. Gilmore and C. S. Morris, IAUC, No. 4975 (1990 Mar. 7); Z. Sekanina, R. M. West, and A. C. Gilmore, IAUC, No. 4977 (1990 Mar. 8); B. G. Marsden, MPC, No. 16001 (1990 Mar. 11); A. Hale and J. E. Bortle, IAUC, No. 4983 (1990 Mar. 23); B. G. Marsden, IAUC, No. 4985 (1990 Mar. 27); M. Fulle and L. Pansecchi, IAUC, No. 4991 (1990 Apr. 10); A. Hale, R. A. Keen, C. S. Morris, A. R. Pearce, and D. A. J. Seargent, ICQ, 12 (1990 Apr.), pp. 44, 63–4; B. G. Marsden, MPC, No. 16205 (1990 Apr. 10); D. W. E. Green, IAUC, No. 5001 (1990 Apr. 27); D. J. Sahnow, P. D. Feldman, S. R. McCandliss, and M. E. Martinez, IAUC, No. 5010 (1990 May 11); M. C. Festou, M. F. A’Hearn, S. A. Budzien, P. D. Feldman, and E. E. Roettger, IAUC, No. 5012 (1990 May 16); D. W. E. Green, IAUC, No. 5014 (1990 May 17); D. Bockelée-Morvan, D. Despois, G. Paubert, P. Colom, and J. Crovisier, IAUC, No. 5020 (1991 May 23); J. Crovisier, D. Despois, D. Bockelée-Morvan, G. Paubert, and P. Colom, IAUC, No. 5022 (1991 May 25); D. Despois, D. Bockelée-Morvan, G. Paubert, P. Colom, and J. Crovisier, IAUC, No. 5027 (1991 May 31); D. W. E. Green, MPC, No. 16378 (1990 Jun. 8); R. M. West, G. Pizarro, and H.-H. Heyer, IAUC, No. 5031 (1990 Jun. 14): J. E. Bortle, R. J. Bouma, P. Camilleri, G. J. Garradd, A. Hale, M. Möller, C. S. Morris, A. R. Pearce, and K. Takamizawa, ICQ, 12 (1990 Jul.), pp. 76, 90–7; D. W. E. Green, MPC, No. 16551 (1990 Jul. 8); J. E. Bortle, P. Camilleri, A. Hale, R. Haver, W. Hasubick, R. A. Keen, A. R. Pearce, C. S. Morris, and D. A. J. Seargent, ICQ, 12 (1990 Oct.), pp. 130–40; S. Nakano, MPC, No. 17400 (1990 Dec. 2); C. S. Morris, ICQ, 13 (1991 Jan.), p. 26; J. Kobayashi, ICQ, 13 (1991 Oct.), pp. 152–5; B. G. Marsden, CCO, 7th ed. (1992), p. 95; D. J. Sahnow, P. D. Feldman, S. R. McCandliss, and M. E. Martinez, Icarus, 101 (1993 Jan.), pp. 71–83; J. G. de Souza Aguiar, ICQ, 15 (1993 Oct.), p. 158; K. J. Meech correspondence with G. W. Kronk (1994); [Perth], MPC, No. 23153 (1994 Mar. 27); R. J. Bouma, ICQ, 16 (1994 Apr.), p 39; R. W. Panther, ICQ, 27 (2005 Jul.), p. 195; R. R. D. Austin correspondence with G. W. Kronk (2011); P. Camilleri correspondence with G. W. Kronk (2015).

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73P/ Recovered: 1989 December 4.57 (Δ = 2.31 AU, r = 2.24 AU, Elong. = 73
) Schwassmann– Last seen: 1990 October 21.22 (Δ = 2.18 AU, r = 2.14 AU, Elong. = 160
) Wachmann 3 Closest to the Earth: 1990 April 17 (0.3668 AU) Calculated path: VIR (Rec), SER (1990 Feb. 25), OPH (Mar. 16), SER (Apr. 1), 1990 VIII=1989d1 SCT (Apr. 5), AQL (Apr. 9), CAP (Apr. 27), AQR (May 1), CET (May 22) This comet was missed at its 1985 apparition, because it was not well placed for observations. Predictions had been published by S. Nakano (1983) and W. Landgraf (1985). Nakano had calculated a new orbit using the positions from 1979 and included planetary perturbations, while Landgraf had linked the 1930 and 1979 apparitions, included planetary perturbations, and solved for nongravitational effects. After integrating the comet’s motion to 1985, the perihelion date was given as January 11.63 by Nakano and January 11.31 by Landgraf. For the 1990 apparition, Landgraf (1987) took the orbit he calculated for the 1985 apparition and integrated the comet’s motion forward. He predicted the next perihelion date as 1990 May 19.34. The comet was recovered by J. X. Luu, D. C. Jewitt, and S. Ridgway (Mauna Kea, Hawaii, USA) on a single CCD image acquired on 1989 December 4.57 and on five CCD images acquired during December 5.59–5.61. They were using the 224-cm reflector with a Mould R filter. The position on the first image was α = 12h 15.3m, δ = +10
190 (2000). They gave the nuclear magnitude as 19.9 and described the comet as exhibiting a centrally condensed core and a tail in PA 298
. An independent recovery was made by J. B. Gibson (Palomar Observatory, California, USA). Using the 152-cm reflector and a Gunn r filter, he acquired four CCD images during December 9.48–9.50 and four images during December 12.48–12.50. The nuclear magnitude was estimated as 21. Gibson said the images obtained on the first date revealed a slight coma and a tail extending 0.1–0.20 in about PA 285
. No further observations were made until 1990 February, when astronomers at Climenhaga Observatory (Victoria, British Columbia, Canada) and Oak Ridge Observatory (Massachusetts, USA) photographed the comet from the 23rd to the 27th. No physical descriptions were provided. A. Hale (Las Cruces, New Mexico, USA) tried to visually observe the comet using his 41-cm reflector on the 4th and 23rd, but was unsuccessful. He said the comet was probably fainter than magnitude 13.5. R. J. Bouma (Groningen, Netherlands) was also unsuccessful on the 22nd while using his 25-cm reflector. He said the comet was probably fainter than magnitude 13.0. The comet reached a maximum elongation of 111
on March 6. The comet was photographed by R. H. McNaught (Siding Spring Observatory, New South Wales, Australia) on the 1st, 4th, and 7th, using the 51-cm Uppsala Southern Schmidt. After the moon had left the sky, several visual observers were able to follow the comet, generally noting a moderately condensed coma. J. Jahn (Germany) spotted it with his 20-cm reflector on the 17th. 474

cometography: a catalog of comets

He estimated the magnitude as 10.5 and said the coma was 2.00 across. Through his 41-cm reflector, Hale found the coma to be about 10 in diameter on the 19th, and determined the comet’s magnitude as 12.9. On the 21st, P. Camilleri (Cobram, Victoria, Australia) gave the magnitude as 12.1 and the coma diameter as 40 , as seen through his 20-cm reflector. A. R. Pearce (Woodlands, Western Australia, Australia) estimated the comet’s brightness as 12.2 on the 22nd with the aid of his 41-cm reflector. He said the coma was 1.20 across. On the 27th, Bouma used his 25-cm reflector to determine the magnitude 12.6 and the coma diameter as 1.20 . Pearce saw the comet on the 28th, giving the magnitude as 11.9 and the coma diameter as 1.00 . He added that the tail extended 10 in PA 275
. Hale gave the magnitude as 12.1 on the 29th. On March 31, the comet was seen by C. S. Morris (California, USA), using his 26-cm reflector, and Camilleri. Morris said it was magnitude 11.3, with a coma 1.00 across, and a tail extending 40 tail in PA 270
. Camilleri judged the comet’s magnitude as 11.5 and its diameter as 50 . The comet was brightest in April, with several dozen visual observations reported. Pearce and Camilleri were the most prolific observers. Pearce used 20-cm, 26-cm, and 41-cm reflectors from the 3rd to the 29th and indicated the comet brightened from 11.5 to 10.2, while the moderately condensed coma increased in diameter from 1.40 to 1.90 . He also reported a tail, noting a length that varied from 20 to 120 and a position angle that generally rotated from 278
at the beginning of the month to 256
by the end of the month. Camilleri used both 20  80 binoculars and his 20-cm reflector during the month, giving magnitudes that brightened from 10.8 to 9.8. He said the coma generally remained moderately condensed, with a diameter that varied from 30 to 60 . Camilleri only noted a tail from the 24th to the 29th, giving lengths that varied from 100 to 300 and a position angle that generally rotated from 270
to 230
. The comet faded slightly in May, but generally remained moderately condensed. Pearce and M. L. Clark (Australia) were the most prolific observers. Pearce used his 20-cm reflector from the 1st to the 30th. He said the comet faded from 10.1 to 10.7, while the coma diameter seemed to decrease from 2.00 to 1.50 . Pearce said the tail length varied from 30 to 110 during the month, while its position angle generally rotated from 250
to 244
. Clark observed with his 25-cm reflector from the 8th to the 23rd, noting a magnitude that varied from 10.2 to 10.5 and a coma diameter that varied from 1.50 to 2.00 . He also observed a tail, noting a length that varied from 200 to 400 and a position angle that seemed to remain at 235
. After having moved southward since its recovery, the comet attained its most southerly declination of 10
on May 7 and reached a minimum elongation of 66
on May 25. Fading became evident in June, with observers reporting a coma that was slightly to moderately condensed. Pearce and Morris were the most prolific observers. Pearce saw the comet on several nights during the 1st to the 30th, 475

cometography: a catalog of comets

using his 20-cm reflector early in the month and his 41-cm reflector late in the month. He indicated that the magnitude faded from 10.9 to 12.4, while the coma diameter decreased from 1.80 to 1.10 . Morris watched the comet from the 2nd to the 30th with his 26-cm reflector. He noted that it faded from 9.9 to 11.3, while the coma diameter decreased from 1.90 to 1.40 . Clark noted the tail on the 2nd, 3rd, and 4th while using his 25-cm reflector. He said it extended 0.5
in PA 240
on the first two nights and 0.42
in PA 240
on the last night. Only one observation was reported in July. A. R. Pearce (Scarborough, Western Australia, Australia) made the final visual observation of this comet on the 2nd. Using his 26-cm reflector, he gave the magnitude as 12.3 and noted a moderately condensed coma 1.70 across. C. S. Morris (California, USA) looked for the comet using a 51-cm reflector on the 22nd, but saw nothing. He suggested the comet was fainter than magnitude 13.5. After having moved northward since early May, the comet attained a declination of 3
on July 26 and then began a southward motion. R. E. McCrosky and C.-Y. Shao (Oak Ridge Observatory, Massachusetts, USA) were the only observers during the remainder of this apparition. Using the 155-cm reflector, they acquired CCD images on September 16, September 18, and October 17, but provided no physical descriptions. After having moved southward since late July, the comet attained a declination of 9
on October 13 and then began a northward motion. It also reached a maximum elongation of 163
on the same day. The comet was last detected during October 21.21–21.22, when McCrosky and Shao acquired CCD images using the 155-cm reflector. No description was provided. The comet’s position on the last image was α = 1h 21.9m, δ = 8
270 (2000). Multiple apparition orbits have been calculated by B. G. Marsden (1995, 1996, 1999), P. Rocher (1996), S. Nakano (1998, 2000, 2003), and K. Kinoshita (2000). All of these calculations included full planetary perturbations, while only those orbits published from 1996 onward solved for nongravitational effects. The result was a perihelion date of May 19.30 and a period of 5.35 years. Marsden only determined the standard radial (A1) and transverse (A2) nongravitational terms. Using positions from 1979–1985, Marsden (1996) determined the terms as A1 = +0.62 and A2 = +0.0490. Using positions from 1989–1996, Marsden (1999) determined the terms as A1 = +0.98 and A2 = +0.2047. The remaining calculations also solved for the normal (A3) component. Rocher (1996) used positions from 1979–1995 and gave the terms as A1 = +0.59, A2 = +0.0491, and A3 = 0.17. The remaining calculations only used positions from 1989 onward and determined nongravitational terms within the following ranges: A1 = +0.83 to +1.07, A2 = +0.1791 to +0.2197, and A3 = 0.19 to 0.21. The orbit of Rocher (1996) is given below. T ω Ω (2000.0) i q e 1990 May 19.3010 (TT) 198.8076 69.9359 11.4122 0.936288 0.694023

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absolute magnitude: H0 = 11.9, n = 7.45, from visual observations (Meyer) full moon: Nov. 13, Dec. 12, 1990 Jan. 11, Feb. 9, Mar. 11, Apr. 10, May 9, Jun. 8, Jul. 8, Aug. 6, Sep. 5, Oct. 4, Nov. 2 sources: S. Nakano, Nakano Note, No. 429 (1983 Jun. 2); W. Landgraf, MPC, No. 8137 (1983 Sep. 22); W. Landgraf, BAA Handbook for 1984 (1983 Oct.), p. 95; W. Landgraf, MPC, No. 12122 (1987 Aug. 9); J. X. Luu, D. C. Jewitt, and S. Ridgway, and J. B. Gibson, IAUC, No. 4923 (1989 Dec. 18); J. X. Luu, D. C. Jewitt, S. Ridgway, and J. B. Gibson, MPC, No. 15607 (1990 Jan. 11); A. Hale, ICQ, 12 (1990 Apr.), pp. 66–7; [Climenhaga], [Oak Ridge], and R. H. McNaught, MPC, No. 16124 (1990 Apr. 10); R. J. Bouma, J. Jahn, P. Camilleri, A. Hale, A. R. Pearce, and C. S. Morris, ICQ, 12 (1990 Jul.), pp. 102–3; [Oak Ridge], MPC, No. 16482 (1990 Jul. 8); T. Seki, MPC, No. 16773 (1990 Sep. 5); A. R. Pearce and M. L. Clark, ICQ, 12 (1990 Oct.), pp. 163–4; R. E. McCrosky and C.-Y. Shao, MPC, No. 17087 (1990 Nov. 2); R. E. McCrosky and C.-Y. Shao, MPC, No. 17276 (1990 Dec. 2); C. S. Morris, ICQ, 13 (1991 Jan.), p. 59; B. G. Marsden, CCO, 10th ed. (1995), pp. 64–5; A. R. Pearce, ICQ, 17 (1995 Jul.), p. 152; B. G. Marsden, CCO, 11th ed. (1996), pp. 66–7; P. Rocher correspondence with G. W. Kronk (1996); S. Nakano, Nakano Note, No. 667 (1998 Apr. 28); B. G. Marsden, CCO, 13th ed. (1999), pp. 72–3; K. Kinoshita correspondence with G. W. Kronk (2000); S. Nakano, Nakano Note, No. 742 (2000 Dec. 9); S. Nakano, Nakano Note, No. 934 (2003 Apr. 14). 94P/1989 X2 Recovered: 1989 December 11.35 (Δ = 1.73 AU, r = 2.62 AU, Elong. = 148
) (Russell 4) Last seen: 1989 December 12.39 (Δ = 1.72 AU, r = 2.62 AU, Elong. = 149
) Closest to the Earth: 1990 January 17 (1.5391 AU) 1990 XI=1989g1 Calculated path: GEM (Rec) [Did not leave this constellation] B. G. Marsden (1987) calculated a new orbit for the discovery apparition, using 39 positions and perturbations by all nine planets. He then integrated the comet’s motion to this apparition and predicted a perihelion date of 1990 July 7.52. J. B. Gibson (Palomar Observatory, California, USA) recovered this comet on four CCD images obtained during 1989 December 11.35–11.41 while using the 152-cm reflector and a Gunn r filter. He estimated the nuclear magnitude as 19 and described the comet as stellar. The position on the earliest image was α = 7h 34.1m, δ = +26
140 (2000). Gibson confirmed the recovery on the next night, when he acquired four CCD images during December 12.36–12.39. These also proved to be the final observations, with the position on the last image given as α = 7h 33.7m, δ = +26
190 (2000). Multiple apparition orbits have been calculated by Marsden (1989, 1994), S. Nakano (1994, 1997, 1999, 2007), K. Kinoshita (2004, 2010), and L. Maquet (2016). These calculations included full planetary perturbations, while Maquet also solved for nongravitational effects. The result was a 477

cometography: a catalog of comets

perihelion date of July 6.83 and a period of 6.57 years. The orbit of Maquet is given below. T 1990 Jul. 6.826 (TT)

ω 93.0426

Ω (2000.0) 71.0378

i 6.1914

q 2.222212

e 0.366315

absolute magnitude: H10 = 13.5 (Meyer) full moon: Nov. 13, Dec. 12, 1990 Jan. 11 sources: B. G. Marsden, MPC, No. 12136 (1987 Aug. 9); J. B. Gibson and B. G. Marsden, IAUC, No. 4932 (1989 Dec. 29); B. G. Marsden, CCO, 9th ed. (1994), pp. 36, 70; S. Nakano, Nakano Note, No. 603 (1994 Apr. 21); S. Nakano, CCO, 12th ed. (1997), pp. 70–1; S. Nakano, Nakano Note, No. 715 (1999 Nov. 4); S. Nakano, Nakano Note, No. 1456 (2007 Apr. 10); K. Kinoshita correspondence with G. W. Kronk (2004, 2010); L. Maquet correspondence with G. W. Kronk (2016). 159P/LONEOS Precovered: 1989 December 17.18 (Δ = 2.74 AU, r = 3.66 AU, Elong. = 156
) Last seen: 1991 February 19.31 (Δ = 3.65 AU, r = 4.47 AU, Elong. = 142
) Closest to the Earth: 1989 November 25 (2.6693 AU) Calculated path: TAU (Disc), PER (1990 Mar. 8), AUR (Apr. 7), LYN (Aug. 3), LMi (Nov. 11), LYN (Nov. 23), UMa (Dec. 15), LYN (1991 Jan. 18) This comet was discovered on 2003 October 16, in the course of the Lowell Observatory Near-Earth Object Search (LONEOS) program. It was described as magnitude 18.8 and stellar, leading to it being reported as a minor planet. C. W. Hergenrother (Whipple Observatory, Mt. Hopkins, Arizona, USA) obtained images on November 30, which revealed it was actually a comet. B. G. Marsden published an orbit on 2003 December 3 that indicated a period of 14.32 years. Soon afterward, M. Meyer found precovery images on digitized photographic plates that had been exposed in 1989 and 1991 for the Second Palomar Sky Survey. The original plates were Kodak IIIa-F (red) emulsion, covering the red spectrum, and had been exposed using the 122-cm Schmidt telescope at Palomar Observatory (California, USA). The first exposure was obtained during 1989 December 17.18–17.22, with a duration of 70 minutes. The cometary trail appeared slightly diffuse with a magnitude of 18.7. The position was α = 3h 56.4m, δ = +27
290 (2000). The second exposure was obtained during 1991 January 19.25–19.31, with a duration of 85 minutes. The cometary trail was very diffuse, allowing no reasonable brightness measurement. The position was α = 8h 54.8m, δ = +46
140 (2000). Between these two observations, the comet reached a minimum elongation of 13
on 1990 June 28 and a maximum elongation of 152
on 1991 January 26. The comet attained its most northerly declination of +46
on 1991 February 17. 478

cometography: a catalog of comets

Multiple apparition orbits have been calculated by Marsden (2004), K. Kinoshita (2004, 2007), S. Nakano (2004), and P. Rocher (2006). All of these calculations included full planetary perturbations. The result was a perihelion date of 1989 October 21.96–21.97 and a period of 14.40–14.41 years. The orbit of Kinoshita (2007) is given below. T ω Ω (2000.0) i q e 1989 Oct. 21.9592 (TT) 3.8904 56.4630 23.2614 3.647472 0.383984

absolute magnitude: H10 = 11 (Meyer) full moon: Dec. 12, 1990 Jan. 11, Feb. 9, Mar. 11, Apr. 10, May 9, Jun. 8, Jul. 8, Aug. 6, Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28 sources: [LONEOS], C. W. Hergenrother, and B. G. Marsden, IAUC, No. 8248 (2003 Dec. 3); K. Kinoshita correspondence with G. W. Kronk (2004, 2007); M. Meyer and B. G. Marsden, MPEC, No. 2004-A18 (2004 Jan. 3); M. Meyer and B. G. Marsden, IAUC, No. 8263 (2004 Jan. 7); M. Meyer and [Palomar], MPC, No. 50459 (2004 Jan. 7); S. Nakano, Nakano Note, No. 1024 (2004 Jan. 19); P. Rocher correspondence with G. W. Kronk (2006). C/1989 Y1 Prediscovery: 1988 June 13.62 (Δ = 6.27 AU, r = 7.16 AU, Elong. = 149
) (Skorichenko– Discovered: 1989 December 17.71 (Δ = 2.54 AU, r = 2.19 AU, Elong. = 58
) George) Last seen: 1991 March 18.42 (Δ = 3.89 AU, r = 4.33 AU, Elong. = 110
) Closest to the Earth: 1990 March 11 (2.1364 AU) 1990 VI=1989e1 Calculated path: AQL (Pre), SCT (Jul. 26), AQL (Dec. 2), DEL (1989 Apr. 16), SGE (Jun. 16), VUL (Jun. 30), LYR (Aug. 12), HER (Sep. 21), VUL (Nov. 2), CYG (1990 Jan. 12), PEG (Feb. 2), LAC (Feb. 8), AND (Feb. 21), PER (Apr. 10), AUR (May 10), TAU (May 30), GEM (Jun. 8), CMi (Jul. 21), HYA (Aug. 18), PYX (Nov. 7), VEL (Dec. 19), PUP (1991 Jan. 24) B. N. Skorichenko (Mezmay, Krasnodar Krai, Russia) discovered this comet on 1989 December 17.71 using a 15-cm reflector. He estimated the magnitude as 10 and gave the position as α = 19h 53.6m, δ = +25
370 (2000). D. B. George (Indian River Observatory, Ontario, Canada) discovered this comet on 1989 December 18.03, while sweeping for comets using a 40-cm reflector. According to the Newsletter of the Royal Astronomical Society of Canada, George said, “I almost ignored this nebulous object that looked almost like a cloud.” He checked a star chart of the field and found nothing there and then “my heart started to pump fast.” George noted movement after 45 minutes and then headed home to report his find to the Central Bureau for Astronomical Telegrams (Cambridge, Massachusetts, USA). He had spent 65 hours searching for comets. He estimated the magnitude as 13. The comet was confirmed by A. Hale (Las Cruces, New Mexico, USA) on December 19.07 and D. H. Levy (Tucson, Arizona, USA on December 19.12. Both were using 41-cm reflectors. Hale gave the magnitude as 10.5 and said 479

cometography: a catalog of comets

the comet was diffuse with a central brightening. Levy gave the magnitude as 10.4 and said the comet was diffuse with a slight condensation. He added that the coma was 20 across, while a faint sunward fan was seen at PA 240
. A prediscovery image of this comet was found by M. Meyer during the course of research for this book. The comet appeared as a bright trail of magnitude 18.5 on a photograph exposed during 1988 June 13.62–13.69 for the SERC-ER survey. The survey used the 122-cm Schmidt telescope at Siding Spring Observatory (New South Wales, Australia). The position was α = 19h 22.4m, δ = 8
320 (2000). The comet reached a maximum elongation of 165
on July 8. After having moved northward since the prediscovery image was obtained, the comet attained a declination of 7
on August 22. It then moved southward until it reached a declination of 8
on October 13, at which time it again began moving northward. The comet reached a minimum elongation of 17
on 1989 January 11 and a maximum elongation of 134
on July 19. After having moved northward since last October, the comet attained a declination of +27
on August 23. It then moved southward until attaining a declination of +24
on November 12, before resuming the northward motion. The comet was well observed during the remainder of December, with observers reporting it as slightly to moderately condensed. R. A. Keen (Mt. Thorodin, Colorado, USA), C. S. Morris (Whitaker Peak, California, USA), and J. E. Bortle (Stormville, New York, USA) made observations on the 20th. Keen was using his 15-cm reflector, giving the magnitude as 9.8 and the coma diameter as 20 . Morris saw the comet with his 26-cm reflector. He judged the magnitude as 10.2 and said the coma was 2.30 across. Bortle observed with his 32-cm reflector, giving the magnitude as 10.2 and the coma diameter as 1.50 . R. J. Bouma (Groningen, Netherlands) observed the comet using a 25-cm reflector on the 21st and determined its magnitude as 10.5. The coma diameter was assessed as 1.8’. Hale saw the comet on the 24th and determined the magnitude as 10.3. A. Nakamura (Kuma, Ehime, Japan) used a 20-cm reflector on the 27th to determine the comet’s magnitude as 10.7 and its diameter as 1.10 . On the 29th, a seven-minute photographic exposure by H. Mikuz (Slovenia), using a 20-cm BakerSchmidt with Kodak Technical Pan 2415 hypered film, revealed a stellar condensation within the 10 coma and a fanning of the coma in PA 222
, but no true tail. Using a 26-cm reflector, Morris estimated the magnitude as 10.0 and the coma diameter as 1.90 on the 30th and as 9.9 and 1.60 , respectively, exactly twenty-four hours later. The comet slightly brightened in 1990 January and was generally described as slightly condensed. The magnitude was given as 10.1 by Hale on the 2nd, while Nakamura judged it to be 9.7 on the 13th. The latter observer also reported a coma diameter of 30 . Another seven-minute exposure was obtained by Mikuz on the 14th, which recorded a tail extending 50 in PA 245
. That same night, Hale again noted the magnitude as 10.1. An 480

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eight-minute exposure by Mikuz on the 17th revealed a fan-shaped tail extending 40 in PA 248
. Bouma gave the magnitude as 9.7 on the 18th and noted a coma 2.20 across. Morris determined the magnitude as 9.6 on the 21st and said the coma diameter was 2.3’. P. E. Roques (Williams, Arizona, USA) photographed the comet on the 22nd, using a 41-cm reflector and Kodak Technical Pan film. He said it revealed a coma 2800 across with a central condensation 1200 across. There was also a long, diffuse, faint tail that extended 5600 in PA 235
. Bouma judged the magnitude as 9.7 on the 26th and said the coma was 2.20 across. The comet was seen by Morris and Nakamura on the 27th. Morris gave the magnitude as 9.5 and said the coma was 3.60 across. He also reported a short, fan-shaped tail extending toward PA 340
. Nakamura determined the magnitude as 9.6 and said the coma was 2.60 across. On the 28th, Hale gave the magnitude as 9.8 and suspected “a faint, stubby tail-like structure extending a few arcmin to the NW. . ..” Morris again reported the tail on the 28th, describing it as a “short fan tail” between about PA 310
and 340
. The comet changed very little in brightness in February, with visual observers noting a slightly to moderately condensed coma. Keen used his 15-cm reflector on the 1st to determine the magnitude as 9.8 and the coma diameter as 30 . On the 5th, S. Korth (Germany) used his 15  80 binoculars to determine the magnitude as 8.9 and the coma diameter as 20 . Bouma gave the magnitude as 9.3 on the 9th. He also noted the coma was about 20 across. On the 11th, J. Jahn (Germany) observed with his 20-cm reflector and judged the magnitude as 9.1. The magnitude was given as 9.6 by Hale on both the 16th and 19th. He said “the tail-like structure noticed on Jan. 28 was not seen on Feb. 16, but was suspected again” on the 19th. Bortle saw the comet with his 20  120 binoculars on the 18th, noting a magnitude of 9.7 and a coma 2.40 across. The magnitude was given as 9.1 by G. R. Chester (Virginia, USA) on the 21st while using his 37-cm reflector. He added that the coma diameter was 30 , while the tail extended about 50 in PA 20
. On the 22nd, Bortle determined the magnitude as 9.5 and the coma diameter as 2.40 . Bouma gave the magnitude as 8.9 on the 23rd and said the coma was 2.00 across. Bortle switched to his 32-cm reflector on the 27th. He gave the magnitude as 9.5 and said the coma was 2.20 across. Mikuz photographed the comet on the 21st and 24th, using a 20-cm reflector and Kodak Technical Pan 2415 hypered film. The six-minute exposure on the first night revealed a strongly condensed coma 10 across and a fan-shaped tail extending 80 in PA 270
. He obtained an eight-minute exposure on the second night. This revealed a strongly condensed coma 1.20 across and a fan-shaped tail extending 30 in PA 260
. This comet was most observed in March and was generally described as slightly to moderately condensed. Four observers reported seeing the comet on eight nights during the month: Bouma, B. H. Granslo (Norway), Jahn, and V. L. Korneev (Zelenograd, Russia). Bouma and Granslo gave no clear indication of a brightness trend. Bouma observed from the 16th to the 30th, 481

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giving magnitudes of 9.0–9.3 and coma diameters of 1.9–2.20 , while Granslo observed with his 20-cm reflector from the 12th to the 30th, giving magnitudes of 8.7–9.5 and coma diameters of 2.5–3.30 . Jahn and Korneev indicated that the comet faded during the month. During the 14th to the 31st, Jahn indicated a drop from 8.8 to 9.8, while the coma diameter varied from 1.20 to 3.10 . Korneev observed with his 20-cm refractor from the 4th to the 21st. He noted that the brightness faded from 8.9 to 9.3. With the aid of a 32-cm reflector, O. Midtskogen (Norway) observed a faint tail. He said it extended 30 in PA 210
on the 12th, 3.60 in PA 330
on the 19th, 30 in PA 320
on the 24th, and 2.40 in PA 325
on the 26th. The comet attained its most northerly declination of +43
on March 25. The comet was clearly fading in April and visual observers almost unanimously agreed that the coma was slightly condensed. Jahn reported a magnitude of 9.4 on the 4th and gave the coma diameter as 1.70 . One day later, he gave the magnitude as 9.9 and the coma diameter as 1.90 . According to Bortle, the comet faded from a magnitude of 9.3 on the 13th to 10.0 on the 19th, as observed with his 32-cm reflector. He indicated that the coma diameter remained fairly constant, being estimated as 1.90 on the first date and 1.80 on the last date. Using his 26-cm reflector, Morris estimated the magnitude as 9.8 and the coma diameter as 20 on the 22nd, while Nakamura gave 10.2 and 1.60 , respectively, on the 24th. Bouma gave the magnitude as 9.3 and said the coma was about 20 across on both the 22nd and 25th. On April 27, Midtskogen gave the magnitude as 9.7 and the coma diameter as 20 . As the comet faded, it was also dropping into evening twilight. Subsequently, only two observers reported observations in May: Jahn and T. Seki (Geisei, Kochi, Japan). Jahn saw the comet with his 20-cm reflector on the 1st and determined the magnitude as 10.6. He also noted a slightly condensed coma 1.1’ across. As it turned out, this would be the final visual observation. Seki photographed the comet on the 15th, using his 60-cm reflector, and estimated the magnitude as 15. The comet reached a minimum elongation of 5
on July 1 and eventually entered the morning sky. Hale attempted observations on September 27 and October 27, but was unsuccessful. He estimated that the comet was probably fainter than magnitude 12.5 on the first night and fainter than 13.0 on the second night. Hale blamed skyglow and the comet’s low altitude for his failure to see the comet on both nights, adding faint twilight was also an issue on the first night. R. J. Modic (Ohio, USA) looked for the comet on October 20, using his 36-cm reflector, but was unsuccessful. He suggested that the comet was probably fainter than 12.5. Only six observations were acquired during the remainder of 1990. R. H. McNaught (Siding Spring Observatory, New South Wales, Australia) obtained photographs on October 16 and 17, using the 51-cm Uppsala Southern Schmidt telescope. He estimated the magnitude as 15 on the first night. Seki obtained two photographs on October 30 and estimated the 482

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magnitude as 14. A. C. Gilmore and P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) obtained two photographs on December 27 and gave the nuclear magnitude as 17.5. The comet was moving southward as 1991 began and attained its most southerly declination of 43
on February 2. It also reached a maximum elongation of 119
on February 7. Also on the 7th, McNaught acquired two more photographs. These revealed that the comet was “strongly condensed with [a] very faint coma.” He estimated the magnitude as 17. Gilmore and Kilmartin obtained two photographs on March 8, judging the nuclear magnitude as 18.4. This comet was last detected on 1991 March 18.42, when S. M. Hughes (Siding Spring Observatory) obtained a 55-minute exposure on a Kodak IIIa-F (red) photographic plate using the 122-cm Schmidt telescope. McNaught examined the plate and described the comet as “faint,” with an estimated the magnitude as 18. The position was α = 7h 42.1m, δ = 39
360 (2000). The spectrum of this comet was examined on 1990 February 26 by V. L. Afanasiev, K. I. Churyumov, and A. I. Shapovalova (Special Astrophysical Observatory, Nizhny Arkhyz, Russia) using a TV spectral scanner attached to the 605-cm reflector. K. I. Churyumov, G. F. Chorny, and V. V. Kleshchonok (1997) wrote that among the emissions were cyanogen, diatomic carbon, methylidyne, triatomic carbon, the imidyl radical, sodium, and neutral carbon monoxide. The first orbit was calculated by S. Nakano. It was parabolic and was published on 1989 December 23. Using nine positions from December 20–23, he determined the perihelion date as 1990 April 14.04. As further positions were reported, additional parabolic orbits were calculated during the next few months. B. G. Marsden published an orbit on 1990 January 11 which gave the perihelion date as April 11.94. Additional orbits by Nakano were published on February 9, April 10, and June 8, the latter of which gave the perihelion date as April 11.91. The first hyperbolic orbit was calculated by Nakano and was published on December 2. He took 81 positions from 1989 December 20 to 1990 October 30 and included full planetary perturbations. He determined the perihelion date as April 11.93 and the eccentricity as 1.00030. The only orbit that was calculated using positions from the entire apparition came from K. Muraoka (1992). He used 93 positions and included full planetary perturbations. The result was a perihelion date of April 11.93 and an eccentricity of 1.00031. This orbit is given below. The 7th edition of Marsden’s Catalogue of Cometary Orbits included original and future orbits for this comet. Both were found to be elliptical, with periods of about 2.6 million years and 62 thousand years, respectively. T ω Ω (2000.0) i q e 1990 Apr. 11.9292 (TT) 137.8329 280.0093 59.3660 1.569172 1.000308

483

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absolute magnitude: H0 = 5.7, n = 2.5 (Kronk) full moon: May 31, Jun. 29, Jul. 29, Aug. 27, Sep. 25, Oct. 25, Nov. 23, Dec. 23, 1989 Jan. 21, Feb. 20, Mar. 22, Apr. 21, May 20, Jun. 19, Jul. 18, Aug. 17, Sep. 15, Oct. 14, Nov. 13, Dec. 12, 1990 Jan. 11, Feb. 9, Mar. 11, Apr. 10, May 9, Jun. 8, Jul. 8, Aug. 6, Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30 sources: D. B. George, A. Hale, and D. H. Levy, IAUC, No. 4925 (1989 Dec. 19); B. N. Skorichenko and S. Nakano, IAUC, No. 4929 (1989 Dec. 23); B. N. Skorichenko, IAUC, No. 4935 (1989 Dec. 30); A. Hale and C. S. Morris, ICQ, 12 (1990 Jan.), p. 12; B. G. Marsden, MPC, No. 15673 (1990 Jan. 11); D. B. George, Newsletter of The Royal Astronomical Society of Canada, 2 (1990 Feb.), p. 6; B. N. Skorichenko and D. B. George, SACNEWS, No. 157 (1990 Feb.); S. Nakano, MPC, No. 15857 (1990 Feb. 9); R. A. Keen, J. E. Bortle, C. S. Morris, H. Mikuz, A. Hale, P. E. Roques, J. Jahn, G. R. Chester, B. H. Granslo, and O. Midtskogen, ICQ, 12 (1990 Apr.), pp. 44, 65–6; S. Nakano, MPC, No. 16205 (1990 Apr. 10); S. Nakano, MPC, No. 16378 (1990 Jun. 8); R. J. Bouma, H. Mikuz, S. Korth, J. E. Bortle, J. Jahn, V. L. Korneev, and C. S. Morris, ICQ, 12 (1990 Jul.), pp. 98–9; T. Seki, MPC, No. 16482 (1990 Jul. 8); R. H. McNaught, MPC, No. 17087 (1990 Nov. 2); T. Seki and S. Nakano, MPC, Nos. 17276, 17400 (1990 Dec. 2); A. C. Gilmore, P. M. Kilmartin, and R. H. McNaught, MPC, No. 17684, 17688 (1991 Feb. 28); A. Hale and R. J. Modic, ICQ, 13 (1991 Apr.), pp. 70, 76; A. C. Gilmore, P. M. Kilmartin, and R. H. McNaught, MPC, No. 18011 (1991 Apr. 28); A. Nakamura, ICQ, 13 (1991 Oct.), pp. 155–6; B. G. Marsden, CCO, 7th ed. (1992), p. 96; V. L. Afanasiev, K. I. Churyumov, A. I. Shapovalova, G. F. Chorny, and V. V. Kleshchonok, Astronomical and Astrophysical Transactions, 13 (1997), pp. 225–31; K. Muraoka, MPC, No. 20308 (1992 Jun. 15); S. M. Hughes, R. H. McNaught correspondence with G. W. Kronk (2015). C/1989 Y2 Prediscovery: 1989 December 2.65 (Δ = 1.14 AU, r = 2.00 AU, Elong. = 139
) (McKenzie– Discovered: 1989 December 21.52 (Δ = 1.11 AU, r = 2.05 AU, Elong. = 156
) Russell) Last seen: 1990 January 24.30 (Δ = 1.59 AU, r = 2.19 AU, Elong. = 96
) Closest to the Earth: 1989 December 13 (1.0705 AU) 1989 Calculated path: CMi (Pre), MON (Dec. 3), ORI (Dec. 10), TAU (Dec. 24), ERI XVIII=1989f1 (1990 Jan. 1), TAU (Jan. 6), CET (Jan. 11), ERI (Jan. 17) P. McKenzie discovered this comet on a photographic plate exposed for 70 minutes during 1989 December 21.52–21.56 by K. S. Russell (Siding Spring Observatory, New South Wales, Australia) using the 122-cm Schmidt telescope. McKenzie was putting the processed and washed plate in the drying rack and, as she checked that the wash was uniform, she noted the obvious trail of a comet with a tail. The diffuse trail was magnitude 14 and was described as strongly condensed, with a tail extending 150 toward PA 50
. The position at the beginning of the exposure was α = 5h 04.2m, δ = +2
520 (2000). An independent discovery was made by A. Mrkos 484

cometography: a catalog of comets

(Klet Observatory, Czech Republic) when he found the comet on a 20-minute exposure acquired with the 63-cm reflector on December 26.83. The comet had reached a maximum elongation of 161
on December 15. Quick confirmations came from R. H. McNaught (Siding Spring Observatory) and T. Seki (Geisei, Kochi, Japan). McNaught acquired a photograph on December 24.50 using the 51-cm Uppsala Southern Schmidt telescope and estimated the magnitude as 13. He noted the comet was strongly condensed, with a tail extending 50 in PA 50
. Seki photographed the comet on December 24.65 using his 60-cm reflector. He estimated the magnitude as 13 and described the comet as diffuse, with a central condensation, and exhibiting a tail extending 3000 in PA 45
. Prediscovery images of the comet were found by T. Kojima (Chiyoda, Gunma, Japan) and N. Sato (Chichibu, Saitama, Japan) on photographs obtained using 25-cm reflectors. Kojima located the comet on a five-minute exposure obtained on December 2.65 and estimated the magnitude as 14. The position was α = 7h 14.6m, δ = +8
170 (2000). Sato located it on a 29-minute exposure acquired on December 19.60 and estimated the magnitude as 13. Although he noted the image was poor, he did note a tail extending 30 in PA 50
. The comet was well observed during the remainder of December. P. E. Rogues (Williams, Arizona, USA) photographed it using a 10-cm Schmidt telescope on the 24th and noted the tail extended 50 in PA 48
. A. R. Pearce (Scarborough, Western Australia, Australia) visually observed the comet with his 41-cm reflector on the 25th and gave the magnitude as 13.0. He noted a slightly condensed coma 1.00 across. Two days later, A. Boattini (Piazzano, Italy) saw the comet using his 40-cm reflector and judged the magnitude as 12.8, while photographs by Seki, A. Sugie (Dynic Astronomical Observatory, Shiga, Japan), and P. Rychtarcik (Skalnaté Pleso Observatory) on the same night revealed magnitude estimates of 13, 13, and 12, respectively. Pearce gave the magnitude as 13.3 on December 28 and said the slightly condensed coma was 1.00 across. A photograph by Kojima on the same night revealed a tail extending 20 in PA 50
. On the 29th, a seven-minute photographic exposure by H. Mikuz (Slovenia), using a 20-cm Baker-Schmidt with Kodak Technical Pan 2415 hypered film, revealed a strongly condensed coma 0.50 in diameter and a tail extending 120 in PA 60
. On the 30th, the magnitude was determined as 13.0 by C. S. Morris (Pine Mountain Club, California, USA) and 13.4 by Pearce. Pearce still noted a slightly condensed coma 1.00 across. Only a few observations were reported in 1990 January. On the 1st, A. Hale (Las Cruces, New Mexico, USA), Pearce, and S. Garro (France) gave the magnitude as 12.3, 13.4, and 13.5, respectively. Hale was using a 41-cm reflector. Pearce noted a slightly condensed coma 0.80 across. Garro was using a 20-cm reflector and reported a slightly condensed coma 10 across. That same night, Roques and Kojima obtained photographs that revealed the tail. Roques said it extended 100 in PA 60
, while Kojima 485

cometography: a catalog of comets

noted it extended 0.20 in PA 50
. Another photograph by Roques on the 2nd revealed the tail extending 120 in PA 64
. Pearce saw the comet on the 5th, noting the magnitude as 13.5. He added that the coma was slightly condensed and 0.70 across. Following interference from moonlight, Hale tried to find the comet on the 14th and 15th, but was unsuccessful. He suggested the comet was fainter than 13.0 on the first night and fainter than 13.5 on the second night. J. Kobayashi (Kumamoto, Kumamoto, Japan) saw the comet with a 31-cm reflector on January 21. He gave the magnitude as 13.8 and noted the coma was strongly condensed and 0.50 across. The final astrometric positions were acquired on January 21.40 and January 21.45, when Kojima photographed the comet using a 25-cm reflector. The position was α = 2h 57.0m, δ = 1
240 (2000) on the last date. The final observation was obtained on January 24.30, when D. H. Levy (Catalina Station, Mt. Bigelow, Arizona, USA) visually saw the comet using the 154-cm reflector. He gave the magnitude as 15.0 and noted an uncondensed coma 10 across. The first orbit was calculated by B. G. Marsden and was published on 1989 December 27. It was a parabolic orbit and was based on five positions from December 21–27. The resulting orbit had a perihelion date of 1989 November 8.43. S. Nakano calculated an orbit that was published on 1990 January 4. This used 12 positions from December 19–30 and determined the perihelion date as November 7.72. Nakano published a revised orbit on February 9. Using 21 positions from December 2 to January 4, he determined the perihelion date as November 7.70. Marsden (1991) calculated the only orbit using positions from the entire period of visibility. Using 28 positions, he calculated a parabolic orbit with a perihelion date of November 7.69. This orbit is given below. T 1989 Nov. 7.6939 (TT)

ω 191.7410

Ω (2000.0) 293.8975

i 160.3369

q 1.975817

e 1.0

absolute magnitude: H0 = 4.4, n = 10.3, from visual observations (Meyer) full moon: Nov. 13, Dec. 12, 1990 Jan. 11, Feb. 9 sources: P. McKenzie, K. S. Russell, R. H. McNaught, and T. Seki, IAUC, No. 4930 (1989 Dec. 26); B. G. Marsden, IAUC, No. 4931 (1989 Dec. 27); A. R. Pearce and A. Boattini, IAUC, No. 4933 (1989 Dec. 29); N. Sato, P. Rychtarcik, A. Mrkos, and S. Nakano, IAUC, No. 4938 (1990 Jan. 4); P. E. Rogues, C. S. Morris, A. Hale, and A. R. Pearce, IAUC, No. 4939 (1990 Jan. 4); T. Kojima, N. Sato, R. H. McNaught, T. Seki, A. Mrkos, A. Sugie, P. Rychtarcik, and S. Nakano, MPC, Nos. 15773–4, 15857 (1990 Feb. 9); A. R. Pearce, A. Boattini, H. Mikuz, A. Hale, and J. Kobayashi, ICQ, 12 (1990 Apr.), pp. 65–6; T. Kojima, MPC, No. 16124 (1990 Apr. 10); S. Garro, ICQ, 12 (1990 Jul.), p. 99; B. G. Marsden, MPC, No. 17595 (1991 Jan. 30); D. H. Levy, 486

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ICQ, 13 (1991 Jul.), p. 114; P. McKenzie, R. H. McNaught correspondence with G. W. Kronk (2011). 53P/Van Recovered: 1989 December 9.52 (Δ = 4.61 AU, r = 4.32 AU, Elong. = 67
) Biesbroeck Last seen: 1993 October 21.46 (Δ = 5.20 AU, r = 6.04 AU, Elong. = 145
) Closest to the Earth: 1991 July 29 (1.5275 AU) 1991 VI=1989h1 Calculated path: VIR (Rec), LIB (1990 Oct. 4), SCO (Dec. 1), OPH (Dec. 12), SGR (1991 Jan. 20), CAP (Apr. 5), AQR (Apr. 25), CAP (Jun. 14), AQR (Jul. 20), CAP (Aug. 20), AQR (Dec. 1), PSC (1992 Feb. 29), CET (Mar. 23), PSC (Apr. 20), CET (Jun. 24), PSC (Oct. 31), CET (1993 Feb. 17), ARI (Apr. 15), TAU (May 30) Predictions for the return of this comet were published by S. Nakano (1987) and B. G. Marsden (1988). Both astronomers used positions from the 1954, 1966, and 1978 apparitions and included perturbations by all nine planets. The perihelion date was determined as 1991 April 24.70 by Nakano and April 24.71 by Marsden. J. B. Gibson (Palomar Observatory, California, USA) recovered this comet with the 152-cm reflector and a Gunn r filter on four CCD images acquired during 1989 December 9.52–9.55. He described the comet as stellar and estimated the magnitude as 21. The position on the first image was α = 12h 44.6m, δ = 1
280 (2000). Gibson acquired four additional images using the same equipment during December 10.51–10.53, before announcing the recovery. K. J. Meech (Mauna Kea, Hawaii, USA) obtained two CCD images of the comet on December 27 and another two during December 28, using the 358-cm Canada–France–Hawaii Telescope. The comet was not observed in 1990. After having moved southward since its recovery, it attained a declination of 3
on January 21. The comet then moved northward until attaining a declination of +4
on May 24, at which time it resumed a southward motion. The comet reached a maximum elongation of 174
on April 1 and a minimum elongation of 5
on November 17. The comet was moving southward as 1991 began and attained its most southerly declination of 18
on January 27. The first person to attempt observations was A. Hale (Las Cruces, New Mexico, USA). Using his 41-cm reflector, he looked for the comet on April 13 and May 12, but surmised it must have still been fainter than magnitude 13.5 and 13.0, respectively. Hale finally spotted the comet on May 23 and 24, when he determined the magnitude as 13.6. A. R. Pearce (Australia) observed the comet with his 41-cm reflector on the 26th. He gave the magnitude as 13.9 and noted a slightly condensed coma 0.4’ across. The comet seemed to change little in brightness in June. C. S. Morris (Lockwood Valley, California, USA) observed it with his 51-cm reflector on the 8th and gave the magnitude as 13.3. He noted a very slight condensation and gave the coma diameter as 1.30 . R. J. Modic (Ohio, USA) saw the 487

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comet with his 40-cm reflector on the 14th. He determined the magnitude as 14.1 and said the coma was slightly condensed and 0.450 across. Hale gave the magnitude as 13.4 on the 16th and 21st. Modic noted that it was magnitude 13.4 on both the 20th and 21st. He added that the coma was slightly condensed and 0.400 across. After having moved northward since late January, the comet attained a declination of 10
on June 19 and then began a southward motion. Modic, Morris, and Pearce managed a few observations in July. Modic saw the comet on five nights from the 9th to the 17th, giving a magnitude that varied from 14.0 to 14.5. He reported a slightly to moderately condensed coma with a diameter that varied from 0.350 to 0.500 . Morris and Pearce independently observed the comet on the 15th, both using a 26-cm reflector. Morris gave the magnitude as 13.3 and said the slightly condensed coma was 0.90 across. Pearce gave the magnitude as 13.5 and said the slightly condensed coma was 0.80 across. The comet was most observed in August, being brighter than in previous months and displaying a moderately condensed coma. Morris went back to using a 51-cm reflector on the 4th and 11th, judging the magnitude as 13.7 and 13.4, respectively. He said the coma was 0.450 across on the first night and 0.670 across on the second night. Hale determined the magnitude as 12.8 on the 6th and 13.3 on the 13th. J. E. Bortle (Stormville, New York, USA) saw the comet with his 50-cm reflector on the 7th. He gave the magnitude as 12.8 and the coma diameter as 0.70 . The comet was observed by Modic during the 7th, 11th, and 12th, using a 20-cm reflector and 40-cm reflector. The magnitude was consistently given as 13.8, while the coma was 0.40–0.500 across. A. Nakamura (Kuma, Ehime, Japan) saw the comet with his 20-cm reflector on the 12th, 13th, and 14th. The magnitude varied from 13.3 to 13.5, while the coma steadily increased in diameter, being 0.70 across on the first night and 0.90 across on the last night. The comet reached a maximum elongation of 178
on August 10. The comet seemed to rapidly fade in September. The final visual observations were obtained by Modic, using his 36-cm reflector. He gave the magnitude as 14.8 on the 1st, adding that the coma was slightly condensed and 0.330 across. Modic gave the magnitude as 14.6 on the 2nd, noting that the coma was slightly condensed and 0.350 across. Hale tried to observe the comet on the 2nd with his 41-cm reflector, but was not successful. He suggested it was probably fainter than magnitude 13.5. Modic was also unsuccessful when he tried to see the comet with his 40-cm reflector on the 7th and 29th. He suggested the comet was then fainter than 15.0 and 15.1, respectively. As part of a survey to discover new Trojan minor planets, E. W. Elst examined photographic plates that had been obtained at La Silla Observatory (Chile). The plates were exposed using either the 100-cm Schmidt telescope or 40-cm astrograph. Comet 53P/Van Biesbroeck was accidentally photographed twice in 1991, but was reported as a minor planet on 488

cometography: a catalog of comets

both occasions. The first detection came on August 4 and was given the preliminary designation 1991 PO25. The next detection came on September 4, with a follow-up observation on the 6th. It was designated 1991 RE12. The magnitude of the September object was estimated as 15.0. In both cases, the objects were identified as comet 53P by S. Nakano (1992, 1993). The comet was moving southward as October began, but after attaining a declination of 17
on the 8th, it began a northward motion. The only observations that were made during October came from R. E. McCrosky and C.-Y. Shao (Oak Ridge Observatory, Massachusetts, USA). Using the 155-cm reflector, they acquired CCD images of the comet on the 4th, 5th, 7th, and 8th; however, no physical descriptions were provided. Morris did attempt a visual observation using his 51-cm reflector on the 6th, but was unsuccessful. He suggested the comet was then fainter than magnitude 14.0. The only other observation reported during the remainder of 1991 was a visual one by Nakamura on November 3. Using a 73-cm reflector, he determined the magnitude as 13.8, noting a moderately condensed coma 0.80 across. The comet was lost in twilight as 1992 began, passing just 3
from the Sun on March 27. It was also moving northward and attained a declination of +9
on August 1, after which it moved southward. The earliest detection of the comet was by astronomers at El Leoncito (Argentina) when they acquired two CCD images on October 19, using the 215-cm reflector. J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton (2000) analyzed these images as part of a program to study cometary nuclei. They determined the magnitude as 19.6–19.7. They said the comet “was active” and concluded that the radius of the nucleus was less than 6.3 kilometers. J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired CCD images on October 23 while using the 91-cm reflector. He gave the magnitude as 17.9. The comet reached a maximum elongation of 172
on October 25. The only other observations made in 1992 also came from Scotti, when he used the same equipment to obtain images on December 2. He determined the magnitude as 18.3–18.5 and noted a coma diameter of 1100 . After having moved southward since the beginning of August, the comet attained a declination of +4
on December 9 and then began a northward motion. The first observations acquired in 1993 came from Scotti on January 23. He determined the magnitude as 19.7, the nuclear magnitude as 21.5–22.3, and the coma diameter as 900 . The comet reached a minimum elongation of 5
on May 7 and attained its most northerly declination of +14
on August 9. The comet was last detected during 1993 October 21.40–21.46, when Scotti acquired three CCD images using the 91-cm reflector. He gave the magnitude as 20.7–22.0 and the nuclear magnitude as 23.1. He added that the coma was 1200 across, while a tail extended about 3600 toward PA 256
. The position at the time of the final observation was α = 4h 07.5m, δ = +13
060 (2000). 489

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Multiple apparition orbits have been calculated by G. Forti (1989), K. Muraoka (1992), Nakano (1999, 2013), P. Rocher (2004, 2015), and K. Kinoshita (2003, 2006, 2014). All of these calculations included full planetary perturbations, while all but Muraoka (1992) solved for nongravitational effects. The result was a perihelion date of April 24.68–24.70 and a period of 12.43 years. Forti determined nongravitational terms of A1 = 0.00 and A2 = 0.0443. Nakano (1999) determined nongravitational terms of A1 = +0.40 and A2 = 0.0248. After adding positions from the 2003 apparition, Kinoshita (2003, 2006, 2014), Rocher (2004), and Nakano (2013) gave nongravitational terms within the following ranges: A1 = +0.16 to +0.26 and A2 = +0.0212 to +0.0259. The orbit of Kinoshita (2014) provides a good fit (residuals 0.69”) for positions acquired for 1954–2014. It is given below. Astronomers have presented very strong evidence suggesting that this comet was once a part of 42P/Neujmin 3. A. Carusi, E. Perozzi, G. B. Valsecchi, and L. Kresák (1984) investigated the motion of both comets and found “a nearly perfect coincidence of the orbital elements of these two comets prior to their close encounters with Jupiter in 1850 Jan.” They suggested “that the two objects are fragments of a single comet that split around that time. . ..” N. A. Belyaev and V. V. Emel’yanenko (1990) examined the orbital motion of these two comets to a greater degree. They found that “introducing even a small number of nongravitational forces allows to diminish significantly the discrepancies in the positions of the comets in close vicinity of the approach.” J. Pittichová, S. J. Bus, and K. J. Meech (2004) acquired spectroscopic observations of both comets on 2004 August 18 using the 996-cm Keck I reflector and the Low Resolution Imaging Spectrometer. They obtained images in the wavelengths 3700–5500 Å (blue) and 5500–7500 Å (red), concluding that the comets were of a similar color, “almost neutral, slightly redder than Sun,” and have a similar molecular column density. They also noted, “53P is a little more dusty than comet 42P.” T ω Ω (2000.0) i q e 1991 Apr. 24.6852 (TT) 134.1710 149.1136 6.6137 2.400900 0.552661

absolute magnitude: H10 = 8.5, from visual observations (Meyer) full moon: Nov. 13, Dec. 12, 1990 Jan. 11, Feb. 9, Mar. 11, Apr. 10, May 9, Jun. 8, Jul. 8, Aug. 6, Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30, Apr. 28, May 28, Jun. 27, Jul. 26, Aug. 25, Sep. 23, Oct. 23, Nov. 21, Dec. 21, 1992 Jan. 19, Feb. 18, Mar. 18, Apr. 17, May 16, Jun. 15, Jul. 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6, Mar. 8, Apr. 6, May 6, Jun. 4, Jul. 3, Aug. 2, Sep. 1, Sep. 30, Oct. 30 sources: A. Carusi, E. Perozzi, G. B. Valsecchi, and L. Kresák, IAUC, No. 3940 (1984 Apr. 25); S. Nakano, Nakano Note, No. 518 (1987 Aug. 20); B. G. Marsden, MPC, No. 13042 (1988 May 1); J. B. Gibson, IAUC, No. 4936 490

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(1989 Dec. 30); N. A. Belyaev and V. V. Emel’yanenko, Asteroids, comets, meteors III; Proceedings of the International Meeting, Uppsala, Sweden, June 12–16, 1989. Uppsala, Sweden (1990), pp. 249–51; J. B. Gibson, MPC, No. 15774 (1990 Feb. 9); G. Forti, MPC, No. 16205 (1990 Apr. 10); A. Hale, IAUC, No. 5276 (1991 May 25); K. J. Meech, MPC, No. 16301 (1990 Jun. 8); B. G. Marsden, BAA Handbook for 1991 (1990 Aug.), p. 78; A. Hale, ICQ, 13 (1991 Jul.), p. 140; R. J. Modic, C. S. Morris, J. E. Bortle, and A. Hale, ICQ, 13 (1991 Oct.), p. 179; R. E. McCrosky and C.-Y. Shao, MPC, No. 18852 (1991 Oct. 23); R. E. McCrosky and C.-Y. Shao, MPC, Nos. 19066–7 (1991 Nov. 21); E. W. Elst, MPC, No. 19243 (1991 Nov. 21); K. Muraoka, CCO, 7th ed. (1992), pp. 34, 68; S. Nakano, MPC, No. 19357 (1992 Jan. 19); A. R. Pearce, ICQ, 14 (1992 Apr.), p. 51; A. Nakamura, ICQ, 14 (1992 Jul.), p. 83; J. V. Scotti, MPC, No. 21157 (1992 Dec. 9); J. V. Scotti and E. W. Elst, MPC, Nos. 21305, 21316, 21507 (1993 Feb. 6); S. Nakano and J. V. Scotti, MPC, Nos. 21628, 21630, 21637 (1993 Mar. 8); J. V. Scotti, MPC, No. 22611 (1993 Oct. 30); J. V. Scotti, ICQ, 16 (1994 Jan.), p. 26; S. Nakano, Nakano Note, No. 718 (1999 Nov. 4); J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton, Icarus, 147 (2000 Sep.), pp. 165, 175–6; K. Kinoshita correspondence with G. W. Kronk (2003, 2006, 2014); P. Rocher correspondence with G. W. Kronk (2004, 2015); J. Pittichová, S. J. Bus, and K. J. Meech, BAAS, 36 (2004 Nov.), p. 1125; S. Nakano, Nakano Note, No. 2480 (2013 Apr. 7). 2P/Encke Recovered: Visible throughout orbit Last seen: Visible throughout orbit 1990 XXI Closest to the Earth: 1990 September 28 (0.7970 AU) Calculated path: AQR (Aphelion), PSC (Apr. 5), AQR (Oct. 6), PSC (1990 Jan. 10), ARI (Jun. 8), TAU (Jul. 30), PER (Aug. 12), AUR (Aug. 19), GEM (Sep. 14), LYN (Sep. 18), CNC (Sep. 20), LEO (Sep. 27), VIR (Oct. 14), LIB (Nov. 5), SCO (Nov. 17), OPH (Nov. 27), SGR (Dec. 8), CAP (1991 Jan. 20), AQR (Mar. 23), CAP (Aug. 14), AQR (1992 Jan. 21), PSC (May 2) Although this comet is visible throughout its orbit, a prediction for this return was still calculated by S. Nakano (1988). He used 86 positions from the years 1973–1987, included full planetary perturbations, and solved for nongravitational effects. He then integrated the comet’s motion to this apparition and predicted a perihelion date of 1990 October 28.55. The comet passed aphelion on 1989 March 8. The first observations were made during 1989 June 1.60–1.66 and June 2.54–2.59, when K. J. Meech (Mauna Kea, Hawaii, USA) acquired seven and 11 CCD images, respectively, using the 224-cm reflector and an R filter. The position on the first image was α = 23h 51.8m, δ = +1
180 (2000). No physical descriptions were provided. Meech remained the only observer during the remainder of 1989, acquiring CCD images on August 1, August 2, and December 27. She used the 491

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224-cm reflector on the first two nights and the 358-cm Canada–France– Hawaii Telescope on the last night. The comet reached a maximum elongation of 176
on September 12. After having moved northward since its recovery, the comet attained a declination of +3
on July 17. It then moved southward until attaining a declination of 5
on November 25, after which it resumed a northward motion. The comet was lost in twilight as 1990 began, reaching a minimum elongation of 4
on March 23. The first definite observation of the year was a visual one by C. S. Morris (Pine Mountain Club, California, USA). Using his 26-cm reflector on August 19, he estimated the magnitude as 12.5 and reported an uncondensed coma 3.00 across. With the same instrument, Morris had suspected seeing the comet 24 hours earlier, but was not able to confirm. The comet reached a maximum elongation of 74
on the 21st. A. Hale (Las Cruces, New Mexico, USA) observed the comet with his 41-cm reflector on the 24th and 25th, giving the magnitude as 11.1 and 11.2, respectively. He described it as “very diffuse” on the first night, while he reported that it was “very vague and diffuse” on the second night. Using a 32-cm reflector, J. E. Bortle (Stormville, New York, USA) “only suspected” seeing the comet on the 30th. He estimated the magnitude as 11.0 and said the coma was about 20 across. That same night, Hale determined the magnitude as 11.0. Bortle gave the magnitude as 10.8 on the 31st and said the coma was uncondensed and 30 across. The comet continued to brighten in September and passed closest to Earth near the end of the month. It attained its most northerly declination of +36
on September 8. The two most prolific observers were Bortle and Morris. Bortle was using his 32-cm reflector early in the month, but switched to his 20  80 binoculars shortly after mid-month. He saw the comet on seven nights from the 1st to the 28th, and indicated the brightness increased from 10.8 to 8.7. Bortle added that the coma was uncondensed on the 1st, but moderately condensed during the last days of the month. He noted a coma diameter of 2.3–2.50 from the 1st to the 18th, and 4.5–5.30 from the 21st to the 28th. Morris saw the comet on seven nights from the 1st to the 25th, reporting that the magnitude brightened from 12.0 to 9.1. He noted the coma diameter increased from 1.90 at the beginning of the month to 90 at the end of the month. Morris also spotted the tail on the 16th while using his 51-cm reflector. He said it extended 70 in PA 90
. The tail was also spotted by A. Renou (France), using his 12-cm reflector. He said it extended about 80 in PA 100
on the 24th, while he only suspected it toward PA 90
on the 28th. The final astrometric position was obtained on October 1.19, when B. Manning (Stakenbridge, England) acquired a single photograph of the comet’s predicted position. The position was α = 9h 52.5m, δ = +24
360 (2000). No description was provided. The comet continued to brighten in October as it approached perihelion and it was kept under visual scrutiny until lost in morning twilight. Bortle 492

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saw the comet on six nights from the 1st to the 17th with his 20  80 binoculars. He noted the comet brightened from 8.6 to 8.1, while the coma diameter decreased from 3.50 to 1.70 . The coma also became more condensed. Bortle saw the comet with 20  120 binoculars on the 20th and 21st, although he only determined a magnitude on the first night (8.3). On both of these nights, he described the coma as strongly condensed and about 1.250 across. Bortle also observed the comet with his 32-cm reflector on the 1st and reported that the “coma possibly opens slightly sunward” along an axis of about PA 105–285
. On the 16th and 17th, Bortle remarked that the coma was almost starlike. Hale followed the comet with 10  50 binoculars and his 41-cm reflector from the 3rd to the 22nd, indicating that the comet brightened from 8.0 on the 3rd, to about 7.3 on the 17th, and then faded to about 7.6 by the 22nd. Hale’s last observation was the final visual one of this apparition. Two observers reported seeing the tail. R. W. Panther (England) saw the comet with his 25-cm reflector on the 1st and said the tail extended toward PA 275
. J. Warell (Sweden) saw the comet with a 6-cm refractor on October 11 and said the tail extended about 60 in PA 250
. During the remainder of the year, the comet was lost in twilight. It reached a minimum elongation of just 4
on November 8 and a maximum elongation of just 12
on December 8. The comet attained its most southerly declination of 29
on December 10. The comet was still lost in twilight as 1991 began, passing just 4
from the Sun on January 18. The only observation reported during this year came from Meech (Cerro Tololo Inter-American Observatory, Chile), when she used the 402-cm reflector and R and I filters to acquire eight CCD images during May 13.40–13.42. She noted that there was possibly a slight coma. The predicted position was α = 22h 44.3m, δ = 11
500 (2000). After having moved northward since last December, the comet attained a declination of 11
on June 7 and then began a southward motion that lasted until it attained a declination of 18
on October 7. The comet also reached a maximum elongation of 177
on August 18. The comet was continuing a northward motion as 1992 began and it was again lost in twilight, passing just 0.1
from the Sun on February 24. The comet passed aphelion on June 19. The spectrum of this comet was examined by U. Fink and M. D. Hicks (1996) on 1990 October 9–11, using the 154-cm reflector and a CCD camera at Catalina Station (Mt. Bigelow, Arizona, USA). They reported the detection of diatomic carbon, cyanogen, the amidyl radical, and water. Multiple apparition orbits have been calculated by Nakano (1990, 1994, 1997, 1999, 2000, 2004, 2005), B. G. Marsden (1997), K. Kinoshita (2000, 2003), and P. Rocher (2000, 2001, 2003). All of these calculations included full planetary perturbations and solved for nongravitational effects. The results were a perihelion date of October 28.57 and a period of 3.28 years. The nongravitational terms were within the following ranges: A1 = 0.02 to +0.02 and A2 = 0.0023 to 0.0010. The orbit of Kinoshita (2003) is given below. 493

cometography: a catalog of comets T ω Ω (2000.0) i q e 1990 Oct. 28.5672 (TT) 186.2356 334.7483 11.9448 0.330891 0.850220

absolute magnitude: H0 = 9.6, n = 2.8 (Shanklin, 1996) full moon: Annual Comet: full moons do not limit the overall period of the comet’s visibility sources: S. Nakano, HBAA for 1989 (1988 Oct.), p. 90; K. J. Meech, MPC, No. 15605 (1990 Jan. 11); K. J. Meech, MPC, Nos. 16296–7 (1990 Jun. 8); C. S. Morris, A. Hale, and J. E. Bortle, IAUC, No. 5085 (1990 Sep. 1); A. Hale, J. E. Bortle, A. Renou, and J. Warell, ICQ, 12 (1990 Oct.), pp. 118, 162; B. Manning, MPC, No. 17086 (1990 Nov. 2); C. S. Morris, J. E. Bortle, and R. W. Panther, ICQ, 13 (1991 Jan.), pp. 7–8, 58–9; S. Nakano, Nakano Note, No, 545 (1991 May 20); K. J. Meech correspondence with G. W. Kronk (1994); S. Nakano, Nakano Note, No. 618 (1994 Apr. 29); J. D. Shanklin, JBAA, 106 (1996 Apr.), pp. 89, 90–1; U. Fink and M. D. Hicks, ApJ, 459 (1996 Mar. 10), pp. 729–43; B. G. Marsden, CCO, 12th ed. (1997), pp. 46–7; S. Nakano, Nakano Note, No. 658 (1997 May 4); S. Nakano, Nakano Note, No. 719 (1999 Nov. 4); K. Kinoshita correspondence with G. W. Kronk (2000, 2003); P. Rocher correspondence with G. W. Kronk (2000, 2001, 2003); S. Nakano, Nakano Note, No. 729 (2000 May 13); S. Nakano, Nakano Note, No. 1045 (2004 Apr. 4); S. Nakano, Nakano Note, No. 1279 (2005 Oct. 28). 116P/1990 B1 Prediscovery: 1990 January 21.58 (Δ = 1.38 AU, r = 2.33 AU, Elong. = 161
) (Wild 4) Discovered: 1990 January 21.98 (Δ = 1.38 AU, r = 2.33 AU, Elong. = 161
) Last seen: 1990 August 18.38 (Δ = 2.59 AU, r = 2.02 AU, Elong. = 46
) 1990 X=1990a Closest to the Earth: 1990 February 20 (1.2673 AU) Calculated path: LEO (Pre), CNC (Feb. 10), LEO (Apr. 28), VIR (Jul. 18) P. Wild (Astronomical Institute of Berne University, Switzerland) discovered this comet on photographic plates exposed with the 40-cm Schmidt camera at Zimmerwald Observatory (Switzerland) on 1990 January 21.98 and January 22.89. He estimated the magnitude as 13.5–14.0. Wild described the comet as “strongly condensed, with a fanshaped tail extending about 10 to the northwest.” The position on the first date was α = 9h 37.3m, δ = +20
260 (2000). Prediscovery images were found by M. Ishikawa (Yorii, Saitama, Japan) and T. Niijima (Ojima, Gunma, Japan) on photographs obtained on January 21. Ishikawa gave positions for January 21.58 and January 21.66, estimating the magnitude as 13.0. Niijima was using a 16-cm hyperboloid astrocamera and gave positions for January 21.69 and January 21.72. He estimated the magnitude as 14. The first visual observations of this comet were made within days of the discovery. A. R. Pearce (Woodlands, Western Australia, Australia) saw it with his 32-cm reflector on the 24th. He gave the magnitude as 13.5 and said the coma was moderately condensed and 0.60 across. A. Hale 494

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(New Mexico, USA) saw it on the 25th with his 41-cm reflector. He determined the magnitude as 12.8 and wrote, “comet small and very condensed; coma is noticeably fan-shaped, with the fan extending westward.” Pearce saw the comet on four more occasions from the 26th to the 31st, consistently noting a moderately condensed coma of magnitude 13.2–13.4, the diameter of which increased from 0.60 to 1.00 . He also noted a tail extending 10 in PA 310
on the 30th. G. W. Kronk (Illinois, USA) and C. S. Morris (Pine Mountain Club, California, USA) reported the comet was slightly condensed. Kronk was using his 33-cm reflector on the 27th and 31st, noting a magnitude of about 12.7 and 12.6, respectively. He said the coma was about 10 across. Morris was observing with his 26-cm reflector and saw the comet on the 27th and 28th. He gave the magnitude as 12.8 and the coma diameter as 0.70 . Morris also saw the tail on both nights, noting that it was 20 long, and said it extended toward PA 330
on the first night. The comet’s brightness slightly increased in February, with most observers estimating magnitudes of between 12 and 13 and reporting a moderately condensed coma. R. J. Bouma (Netherlands) observed from the 3rd to the 23rd using his 25-cm reflector. He noted little change in the comet, determining magnitudes of 12.5–12.7 and noting a coma diameter of 0.7–0.90 . Hale followed the comet from the 4th to the 24th, reporting the brightness increasing from about 12.8 to 12.1. S. Korth (Dusseldorf, Germany) observed with a 36-cm reflector from the 16th to the 22nd. He said the brightness increased from 13.1 to 12.7, while the coma diameter varied from 0.50 to 0.80 . The comet reached a maximum elongation of 174
on February 6. During March, the comet’s brightness remained relatively constant as the comet’s increasing distance from Earth was countered by its decreasing distance from the Sun. The comet attained its most northerly declination of +22
on March 3. B. H. Granslo (Norway) saw the comet using his 20-cm reflector and judged the magnitude as 12.1. He also reported a moderately condensed coma 0.90 across. Granslo would follow the comet on ten more nights from the 12th to the 30th, determining magnitudes of 11.8–12.3. He said the coma remained moderately condensed and 0.9–1.40 across. Hale’s observations from the 3rd to the 28th revealed a very slight brightening from 12.4 to 12.5. Korth generally reported that the comet faded from 12.4 on the 12th to 13.0 by the 18th, while the coma was 0.3–0.50 across. Bouma indicated little change in brightness, as his estimates spanning the 16th to the 30th all fell within the range of 12.4–12.6. He added that the coma remained moderately condensed and 0.8–1.00 across. Two observers noted a tail. J. E. Bortle (Stormville, New York, USA) observed the comet using his 50-cm reflector on the 22nd and noted a tail of uncertain length toward PA 135
. Morris suspected a tail toward PA 90
on the 24th. Bortle also reported a nucleus of magnitude 14.0 on March 22. The comet again showed little sign of fading in April. Korth spotted it on the 1st and judged the magnitude as 12.8. He also noted a moderately 495

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condensed coma 0.40 across. Korth observed it again on the 11th, this time giving the magnitude as 13.5 and the diameter as just 0.20 . Bortle saw the comet on four nights spanning the 13th to the 19th. He indicated that the brightness varied from 12.8–13.0, while the coma was 0.6–0.70 across. Bortle added that the coma was “fan-shaped NW-SE” on the 18th and 19th and noted a possible tail. Pearce saw the comet on five nights from the 16th to the 29th, using his 41-cm reflector. He noted the magnitude varied from 13.0–13.3, while the coma was 0.5–1.20 across. With the aid of a 31-cm reflector, J. Kobayashi (Japan) estimated the comet’s magnitude as 12.5 on April 24, in addition to observing two tails extending 1.80 in PA 100
and 1.20 in PA 265
. Fewer observations were reported in May, although the comet had changed little in brightness. Hale gave the magnitude as 12.6 on the 12th and 12.7 on the 21st, while Morris judged it as 11.9 on both the 14th and 20th. Morris added that the slightly condensed coma was 1.60 across on the first night and 2.20 across on the second night. Pearce’s magnitude estimates varied from 13.0–13.2 from the 14th to the 21st, while the coma remained slightly condensed and 0.9–1.20 across. Bouma gave the magnitude as 13.0 on both the 21st and 25th, while the coma remained 0.80 across and slightly condensed. The final physical descriptions were provided in June and July. T. Seki (Geisei, Kochi, Japan) photographed the comet with his 60-cm reflector on June 11 and estimated the magnitude as 15. Hale saw the comet on June 19 while using his 41-cm reflector and gave the magnitude as 12.9. Morris saw the comet with his 51-cm reflector on July 22. He judged the magnitude as 13.1 and said the slightly condensed coma was 1.30 across. The comet was last detected on August 14.39 and August 18.38, when it was photographed by R. H. McNaught and S. J. Hutcheon (Siding Spring Observatory, New South Wales, Australia) using the 51-cm Uppsala Southern Schmidt telescope. The position on the last date was given as α = 12h 39.5m, δ = 4
480 (2000). The only attempt to examine the spectrum of this comet was made on 1990 January 25 by S. M. Larson and D. H. Levy (Catalina Station, Mt. Bigelow, Arizona, USA). They used the 154-cm reflector and found “a strong continuum, but no cometary emissions.” They added that red-band images revealed a “broad, well-defined tail extending off the CCD frame 40 from the central condensation.” The first parabolic orbit was calculated by B. G. Marsden and was published on 1990 January 25. Marsden used four positions from January 21–25 and determined the perihelion date as 1990 July 16.08. He said, “It is likely that the comet is of short period.” The first short-period orbit was calculated by Marsden and was published on January 31. He used 15 positions from January 21–26, giving the perihelion date as July 4.42 and the period as 6.25 years. During the next few months, as additional positions were reported, new calculations were 496

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published by Wild, S. Nakano, and Marsden. Ultimately, the perihelion date was given as July 2.52, while the period was 6.15 years. K. Muraoka (1992) was the first person to determine an orbit using positions from the entire apparition. He used 147 positions and included full planetary perturbations to reveal a perihelion date of July 2.53 and a period of 6.15 years. Multiple apparition orbits have been calculated by Marsden (1995), K. Kinoshita (1998, 2001, 2003), Nakano (1998, 1999), and P. Rocher (1999, 2003, 2004). All of these calculations included full planetary perturbations, while only those from 1999 onward solved for nongravitational effects. The result was a perihelion date of July 2.52–2.53 and a period of 6.15 years. After two apparitions, it became obvious that nongravitational effects were affecting the orbit of this comet, with the terms being given as A1 = +0.45 and A2 = +1.0899 by Nakano (1997), A1 = +0.17 and A2 = +1.0121 by Nakano (1999), and A1 = +0.54 and A2 = +1.0266 by Rocher (1999). After a third apparition, the calculated terms were within the following ranges: A1 = +1.64 to +1.98 and A2 = +0.5207 to +0.5317. Kinoshita (2001), Rocher (2003), and Rocher (2004) also added the A3 term, indicating a range of +0.10 to +0.14. The orbit of Rocher (2003) is given below. T ω Ω (2000.0) i q e 1990 Jul. 2.5268 (TT) 170.5476 22.1021 3.7211 1.988605 0.407805

absolute magnitude: H0 = 5.9, n = 6 (Shanklin, 1996) full moon: Jan. 11, Feb. 9, Mar. 11, Apr. 10, May 9, Jun. 8, Jul. 8, Aug. 6, Sep. 5 sources: P. Wild, IAUC, No. 4950 (1990 Jan. 23); B. G. Marsden, S. M. Larson, D. H. Levy, A. R. Pearce, and A. Hale, IAUC, No, 4954 (1990 Jan. 25); B. G. Marsden, IAUC, No. 4956 (1990 Jan. 31); P. Wild, A. R. Pearce, and C. S. Morris, IAUC, No. 4963 (1990 Feb. 14); A. R. Pearce, IAUC, No. 4964 (1990 Feb. 15); S. Korth, A. Hale, and B. H. Granslo, IAUC, No. 4974 (1990 Mar. 7); P. Wild, M. Ishikawa, T. Niijima, and S. Nakano, MPC, Nos. 15948–9, 16001 (1990 Mar. 11); A. Hale, C. S. Morris, and B. H. Granslo, ICQ, 12 (1990 Apr.), pp. 44, 67–8; B. G. Marsden, MPC, No. 16205 (1990 Apr. 10); B. H. Granslo and J. E. Bortle, IAUC, No. 4994 (1990 Apr. 17); J. E. Bortle, IAUC, No. 4999 (1990 Apr. 24); J. Kobayashi, A. R. Pearce, and A. Hale, IAUC, No. 5017 (1990 May 21); S. Nakano, MPC, No. 16378 (1990 Jun. 8); R. J. Bouma, S. Korth, A. Hale, J. E. Bortle, C. S. Morris, and A. R. Pearce, ICQ, 12 (1990 Jul.), pp. 103–4; S. Nakano, MPC, No. 16551 (1990 Jul. 8); T. Seki and R. H. McNaught, MPC, Nos. 16773–4 (1990 Sep. 5); A. R. Pearce, R. J. Bouma, and A. Hale, ICQ, 12 (1990 Oct.), p. 167; C. S. Morris, ICQ, 13 (1991 Jan.), p. 60; K. Muraoka, CCO, 7th ed. (1992), pp. 33, 67; G. W. Kronk, ICQ, 15 (1993 Jan.), p. 31; B. G. Marsden, CCO, 10th ed. (1995), pp. 70–1; S. Korth, ICQ, 17 (1995 Jul.), p. 157; J. D. Shanklin, JBAA, 106 (1996 Apr.), pp. 86, 89; S. Nakano, CCO, 12th ed. (1997), pp. 74–5; K. Kinoshita 497

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correspondence with G. W. Kronk (1998, 2001, 2003); S. Nakano, Nakano Note, No. 705 (1999 Nov. 3); P. Rocher correspondence with G. W. Kronk (1999, 2003, 2004); S. Nakano, CCO, 14th ed. (2001), pp. 94–5. C/1990 E1 Prediscovery: 1990 March 13.15 (Δ = 1.43 AU, r = 1.07 AU, Elong. = 49
) (Cernis–Kiuchi– Discovered: 1990 March 14.79 (Δ = 1.41 AU, r = 1.07 AU, Elong. = 49
) Nakamura) Last seen: 1990 May 28.07 (Δ = 1.80 AU, r = 1.57 AU, Elong. = 60
) Closest to the Earth: 1990 April 8 (1.2981 AU) 1990 III=1990b Calculated path: AND (Pre), PER (Mar. 23), AND (Mar. 26), PER (Mar. 30), AUR (Apr. 14), LYN (May 7), GEM (May 15), CNC (May 16) Three observers discovered this comet in less than two days. K. T. Cernis (Vilnius, Lithuania) found the comet using a 12-cm refractor on 1990 March 14.79. He estimated the magnitude as 9 and said the position was α = 0h 57.2m, δ = +43
200 (2000). T. Kiuchi (Usuda, Nagano, Japan) and Y. Nakamura (Yokkaichi, Mie, Japan) independently discovered the comet on March 16.44. They also estimated the magnitude as 9. Kiuchi was using 25  150 binoculars, while Nakamura was using 20  120 binoculars. For Cernis, the weather had been bad during the early months of 1990, and the night of March 14 was the first with clear skies. He traveled to Lavariskes (Lithuania) to the private observatory of his friend H. Selevicius. He brought his 12-cm refractor and began sweeping the sky. After an hour, he swept across the Andromeda Galaxy and a short time later he encountered a “faint diffuse object” of about magnitude 9 in Andromeda. Selevicius took a photograph using his 20-cm reflector. After about half an hour, Cernis detected that the object was moving. He determined a position and, shortly after moonrise, went home. He checked his star atlas and also checked to see if any comets were in the area. As it turned out, his position was about a degree from comet C/1989 Y1 (Skorichenko–George) and he wondered if this was actually the comet that he saw. The next day, Cernis rechecked his measurements and was sure that his position was correct. Skies were predicted to be cloudy on this night and for several more nights. He decided to report his discovery of a possible comet to K. I. Churyumov (Kiev, Ukraine), who sent a notice to the Central Bureau for Astronomical Telegrams (Cambridge, Massachusetts, USA). Cernis left on a business trip the next day. Upon getting back on March 20, Churyumov informed him that he had discovered a comet. He had spent 631 hours searching for comets since his discovery of C/1983 O1 (Cernis). The discovery was confirmed by A. Hale (Las Cruces, New Mexico, USA) on March 17.12 and T. Seki (Geisei, Kochi, Japan) on March 17.47. Hale first detected the comet with the aid of his 41-cm reflector, but switched to a pair of 10  50 binoculars to estimate its magnitude as 8.4. He indicated that a Swan-band filter neither enhanced nor degraded the comet’s visibility. Seki photographed the comet using his 60-cm reflector and gave the magnitude as 9.2. Later, it was learned that a prediscovery observation had been made 498

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by C. E. Spratt (Victoria, British Columbia, Canada), who found the comet with his 20-cm reflector on March 13.15. He was unable to confirm the discovery because of clouds. Spratt estimated the comet’s magnitude as approximately 8.5 at that time. The comet was well observed during the remainder of March, with most observers describing it as moderately condensed. C. S. Morris (Pine Mountain Club, California, USA) saw the comet using 20  80 binoculars on the 18th. He determined the magnitude as 8.7 and the coma diameter as 30 . On that same night, R. J. Bouma (Groningen, Netherlands) saw the comet with 10  50 binoculars. He judged the magnitude as 8.1 and the coma diameter as about 30 . Hale saw the comet with his 10  50 binoculars on the 20th and gave the magnitude as 8.2. That same night, J. Jahn (Germany) observed with his 33-cm reflector, giving the magnitude as 8.8 and the coma diameter as 2.70 . He also noted two tails: one extending 50 in PA 95
and the other extending 50 in PA 200
. J. E. Bortle (Stormville, New York, USA) saw the comet with 10  50 binoculars on the 22nd. He determined the magnitude as 8.2 and said the coma was 3.50 across. Bortle made another observation on the 24th using the same instrument, giving the magnitude as 8.3 and the coma diameter as 30 . Bortle also used his 32-cm reflector on this last date and noted a nucleus of magnitude 12.5–13. Morris also saw the comet on the 24th, but was using 20  80 binoculars. He determined the magnitude as 7.8 and the coma diameter as 30 . Using his 25-cm reflector, Bouma judged the magnitude as 8.1 on the 26th and noted a coma diameter of 2.50 . On the 27th, Bortle gave the comet’s magnitude at 8.9 with binoculars, remarking that it appeared “noticeably fainter” than previously and that the nucleus noted earlier was no longer visible through the 32-cm reflector. Bouma observed the comet on March 30 and estimated its magnitude as 8.5 and diameter as 2.70 . The comet noticeably faded in April and was generally described as slightly condensed. Bouma and Spratt saw the comet on the 1st. Bouma gave the magnitude as 9.0 and the coma diameter as 2.80 , while Spratt judged the magnitude as 8.9 and the coma diameter as 3.50 . S. Korth (Dusseldorf, Germany) saw the comet on the 9th while using a 36-cm reflector. He reported the magnitude as 9.2 and the coma diameter as 30 . Korth also noted a tail extending 9.60 in PA 350
, describing it as “extremely faint and elusive.” The comet attained its most northerly declination of +52
on April 8. Bortle saw the comet on five nights spanning the 12th to the 19th, using his 32-cm reflector. He indicated that the comet faded from 9.0 to 10.0, while the coma diameter varied from 2.30 to 3.70 . Hale saw the comet with his 41-cm reflector on the 21st. He remarked that the comet was “significantly fainter and more diffuse than on previous nights,” giving the magnitude as 9.8. One day later, Morris determined the magnitude as 11.9 and the coma diameter as 20 . Bouma judged the magnitude as 12.3 on the 25th and noted a coma about 20 across. Morris said the magnitude was again 11.9 on the 28th, while the coma was 2.30 across. On April 29, Korth gave the magnitude as 10.2 and the coma diameter as 20 . 499

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Although several visual observers searched for the comet in May, only two were successful. Morris determined the magnitude as 12.2 on the 14th and noted an uncondensed coma 1.80 across. That same night, D. H. Levy (Catalina Station, Mt. Bigelow, Arizona, USA) saw the comet with the 154-cm reflector. He estimated the magnitude as 13.8 and said the coma was slightly condensed and 1.50 across. The comet reached a maximum elongation of 63
on May 8. Seki photographed the comet on May 15 and 26, estimating the magnitude as 17. The comet was last detected on May 28.07, when R. E. McCrosky and C.-Y. Shao (Oak Ridge Observatory, Massachusetts, USA) obtained a CCD image using the 155-cm reflector. The position was α = 8h 44.4m, δ = +25
150 (2000). No descriptive information was provided. The first parabolic orbit was calculated by S. Nakano and was published on 1990 March 19. This used six positions from March 17–19 and revealed a perihelion date of 1990 March 17.13. As additional positions were reported, revised parabolic orbits were published by B. G. Marsden on March 27 and Nakano on May 11, which pinpointed the perihelion date as March 17.33. The only orbit to use positions spanning the entire apparition was calculated by Nakano and was published on July 8. Because of the short observational arc, the orbit was still parabolic. Nakano used 58 positions and determined the perihelion date as 1990 March 17.33. This orbit is given below. T 1990 Mar. 17.3264 (TT)

ω 100.6214

Ω (2000.0) 348.4448

i 48.1425

q 1.068339

e 1.0

absolute magnitude: H0 = 6.8, n = 10.6 (Kronk) full moon: Mar. 11, Apr. 10, May 9, Jun. 8 sources: K. T. Cernis, T. Kiuchi, Y. Nakamura, and A. Hale, IAUC, No. 4980 (1990 Mar. 17); T. Seki and S. Nakano, IAUC, No. 4981 (1990 Mar. 19); B. G. Marsden, C. S. Morris, and J. E. Bortle, IAUC, No. 4986 (1990 Mar. 27); C. E. Spratt, A. Hale, and C. S. Morris, ICQ, 12 (1990 Apr.), pp. 44, 62; B. G. Marsden, MPC, No. 16205 (1990 Apr. 10); C. E. Spratt, IAUC, No. 4992 (1990 Apr. 11); J. E. Bortle, A. Hale, and C. S. Morris, IAUC, No. 5011 (May 11); S. Nakano, MPC, No. 16378 (1990 Jun. 8); R. J. Bouma, J. Jahn, J. E. Bortle, C. S. Morris, C. E. Spratt, S. Korth, and A. Hale, ICQ, 12 (1990 Jul.), pp. 99–101; S. Korth, C. S. Morris, and D. H. Levy, IAUC, No. 5049 (1990 Jul. 5); R. E. McCrosky, C.-Y. Shao, and S. Nakano, MPC, Nos. 16483, 16551 (1990 Jul. 8); K. T. Cernis correspondence with G. W. Kronk (2016). 162P/Siding Precovered: 1990 March 23.26 (Δ = 2.98 AU, r = 3.92 AU, Elong. = 158
) Spring Last seen: 1990 March 23.31 (Δ = 2.98 AU, r = 3.92 AU, Elong. = 157
) Closest to the Earth: 1988 November 7 (0.7731 AU) Calculated path: COM (Disc) [Did not leave this constellation] 500

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This comet was discovered on 2004 October 10 by R. H. McNaught and the Siding Spring Observatory team (New South Wales, Australia). A few weeks later, G. Forti was searching the digital archives and found this comet on an image exposed during 1990 March 23.26–23.31 with the 122-cm Schmidt telescope at Palomar Observatory (California, USA). The original photographic plate had been obtained as part of the Second Palomar Sky Survey, with J. E. Mueller and C. Brewer operating the telescope. Forti described the cometary trail as very faint and located very close to a bright star. M. Meyer has estimated the magnitude as about 19.5. The positions were α = 12h 21.7m, δ = +21
170 on March 23.26 and α = 12h 21.6m, δ = +21
170 (2000) on March 23.31. Multiple apparition orbits have been calculated by K. Kinoshita (2004, 2009), S. Nakano (2004, 2007, 2012), B. G. Marsden (2005), and P. Rocher (2014). These calculations included full planetary perturbations. The result was a perihelion date of 1988 December 1.09 and a period of 5.32 years. The orbit of Nakano (2012) is given below. T ω Ω (2000.0) i q e 1988 Dec. 1.0927 (TT) 356.4861 31.2500 27.8526 1.227026 0.597395

absolute magnitude: H10 = 11.5 (Meyer) full moon: Mar. 11, Apr. 10 sources: R. H. McNaught, MPEC, No. 2004-T55 (2004 Oct. 11); J. E. Mueller, C. Brewer, and G. Forti, MPC, No. 53167 (2004 Nov. 26); S. Nakano, Nakano Note, No. 1124 (2004 Dec. 9); B. G. Marsden, CCO, 16th ed. (2005), pp. 134–5; S. Nakano, Nakano Notes, No. 1448 (2007 Mar. 4); K. Kinoshita correspondence with G. W. Kronk (2009); S. Nakano, Nakano Note, No. 2312 (2012 Jul. 30); P. Rocher correspondence with G. W. Kronk (2014). C/1990 K1 (Levy) Discovered: 1990 May 20.44 (Δ = 3.07 AU, r = 2.59 AU, Elong. = 53
) Last seen: 1992 April 1.11 (Δ = 6.00 AU, r = 6.36 AU, Elong. = 44
) 1990 XX=1990c Closest to the Earth: 1990 August 26 (0.4291 AU) Calculated path: PEG (Disc), AND (Jun. 9), PEG (Jul. 7), EQU (Aug. 19), DEL (Aug. 21), AQL (Aug. 23), SGR (Aug. 28), OPH (Sep. 6), SCO (Sep. 9), LUP (Sep. 21), CEN (Oct. 20), HYA (1991 Jan. 25), CNC (Mar. 27), LEO (Aug. 16), CNC (1992 Jan. 10), LYN (Feb. 27) There is an interesting story behind the discovery of this comet. During 1990 May, D. H. Levy spent a few nights with S. M. Larson (Catalina Station, Mt. Bigelow, Arizona, USA) observing comet C/1989 X1 (Austin) using the 154-cm reflector. The comet had been predicted to become a very bright object and extensive observations had been planned, but it was turning out to be much fainter than predicted. On the morning of May 19, Larson told Levy, “Comet Austin is a one-person job. Tomorrow night you should stay home and find us a bright comet!” 501

cometography: a catalog of comets

So on the morning of May 20, Levy was met with some clouds, but he decided to go through with a comet-hunting session anyway. Although his plan had been to search until the last quarter moon rose, the sky began clearing around the time of moonrise and he decided to continue searching, but pointed the 41-cm reflector toward the north to be as far from the moon as possible. Levy wrote, “I hunted through the constellation of Andromeda, past the bright star Alpheratz, and then I moved into Pegasus. Not far from Alpheratz, a soft fuzzy patch of light entered the field of view. Since I knew this part of the sky very well, I immediately thought this must be a comet.” The time of the observation was given as May 20.44 and the position was α = 23h 56.9m, δ = +27
470 (2000). Levy judged the magnitude as 9.6 and noted a tail extending 20 toward the southwest. The comet did not seem to move during the next hour, but Levy’s check with the Palomar Sky Survey plate of this area revealed no nonstellar object in this position. He announced his discovery to the proper authorities. Three individuals confirmed the comet on May 21. A. Hale (Las Cruces, New Mexico, USA) located the comet on May 21.43 using his 41-cm reflector. He gave the magnitude as 10.1 and said the coma was moderately condensed and about 10 across. C. S. Morris (Pine Mountain Club, California, USA) spotted the comet with his 26-cm reflector on May 21.44. He determined the magnitude as 10.5 and the coma diameter as 1.50 . Morris added that the condensation was nearly stellar. T. Seki (Geisei, Kochi, Japan) photographed the comet on May 21.75 and May 21.79, using his 60-cm reflector. He estimated the magnitude as 11. Several amateur astronomers followed the comet during the remainder of May, with the most prolific observers seeing the comet on five nights. A. R. Pearce (Australia) followed the comet with his 20-cm reflector from the 22nd to the 30th. He indicated that the magnitude varied from 10.2–10.4, while the moderately condensed coma varied from 1.70 to 2.20 across. R. J. Bouma (Groningen, Netherlands) used his 10-cm and 25-cm reflectors and reported that the comet brightened from 10.3 on the 23rd to 9.8 by the 31st. He generally noted a moderately condensed coma, the diameter of which increased from 1.50 to 2.60 . P. Schmeer (Germany) observed the comet with his 20-cm reflector from the 27th to the 31st. He said the comet brightened from 11.2 to 10.8, while the coma appeared slightly condensed and 1–1.50 across. The comet brightened during June, with most observers reporting it as moderately condensed. Morris, Pearce, and R. J. Modic (Ohio, USA) each saw the comet on eight nights. Morris used 20  80 binoculars and said the comet brightened from 9.6 on the 2nd to 8.1 by the 30th, while the coma diameter generally increased from 50 to 6.50 . On both the 23rd and 24th, Morris reported a tail extending 400 in PA 278
, while it was about 50 wide on the first night. Pearce followed the comet with his 20-cm reflector and indicated that from the 1st to the 30th the comet brightened from 10.3 to 8.7. He generally noted that the coma diameter increased from 2.00 to 3.00 502

cometography: a catalog of comets

during the same period. Modic mostly observed using his 20-cm reflector. He reported that the magnitude increased from 9.5 on the 1st to 8.7 by the 26th, while the coma diameter varied from 1.50 to 3.00 . Modic added that the tail extended 40 in PA 270
on the 26th. The comet continued to brighten in July, with most observers reporting a moderately condensed coma. Hale and Modic used 10  50 binoculars to determine the magnitude as 8.3 on the 1st and 2nd, respectively. D. A. J. Seargent (The Entrance, New South Wales, Australia) determined the same brightness through a 15-cm reflector on the 3rd, noting that the comet exhibited a “sharp central condensation” which appeared less prominent when a Swan-band filter was used, although the general visibility of the comet was not noticeably altered by the filter. On the 4th, Morris judged the magnitude as 7.9 and the coma diameter as 70 , as seen through 20  80 binoculars. Modic used 10  50 binoculars on the 7th to determine the magnitude as 8.0. He noticed a tail while using his 20-cm reflector and said it extended 3.60 in PA 270
. J. Jahn (Germany) spotted the comet with a 5-cm refractor on the 12th, giving the magnitude as 8.3 and the coma diameter as 30 . Using 20  80 binoculars, Morris judged the magnitude as 7.5 on the 14th and 7.0 on the 15th. He reported the coma diameter as 50 on the first night and 9’ on the second night. Morris also used his 26-cm reflector on the second night and saw a tail extending 350 in PA 270
. On the 17th, Morris found the comet’s brightness and diameter unchanged from the 15th; however, the tail extended 19.80 in PA 280
. Hale saw the comet using 10  50 binoculars on the 19th, giving the magnitude as 6.7. Switching to his 41-cm reflector revealed a tail extending over 200 in PA 240
. The comet was first spotted with the naked eye by R. Haver (Italy) on the 23rd, when he gave the magnitude as 6.0. Almost four nights later, Haver said the comet had brightened to 5.8. Pearce saw the comet on the 27th, using his 20  80 binoculars. He determined the magnitude as 6.3 and said the tail extended 450 in PA 231
. On the 28th, G. J. Garradd (Tamworth, New South Wales, Australia) said his 10  50 binoculars revealed a magnitude of 5.9 and a tail extending 1.5
. The comet was seen by Morris and Haver on the 29th, giving the magnitude as 6.0 and 5.5, respectively. Haver also noted the coma was 120 across. J. E. Bortle (Stormville, New York, USA) saw the comet with 10  50 binoculars on the 31st. He reported a magnitude of 6.2, a coma diameter of 110 , and a tail extending 1.1
in PA 240
. The comet attained its most northerly declination of +30
on July 10. The comet was most observed during August and remained moderately condensed. Over 2600 observations were reported to the International Comet Quarterly, more than two times the number reported in July, of which almost 350 were made with the naked eye. Bortle followed the comet with the naked eye from the 3rd to the 28th, noting that the magnitude brightened from 5.7 to 4.1, while the coma diameter varied from 300 to 540 . Modic saw the comet with the naked eye from the 2nd to the 30th and indicated that the comet brightened from 5.9 to 4.2. Morris 503

cometography: a catalog of comets

noted that the naked-eye magnitude brightened from 4.5 on the 12th to 3.7 by the 29th, while he reported coma diameters of 340 on the 17th and 510 on the 18th. S. Garro (France) made naked-eye observations from the 16th to the 23rd. He said the comet brightened from 4.2 to 3.6, while the coma diameter varied from 100 to 500 . Although some observers managed to see the tail with the naked eye around mid-month, the best observations were made using optical aid. Bortle observed using 10  50 binoculars from the 2nd to the 28th, reporting tail lengths ranging from 1
to 3.6
, with the longest length coming on the 17th. He said the tail angle decreased from PA 241
to PA 77
during this period. Bouma used 7  50 and 10  50 binoculars from the 1st to the 29th, noting tails lengths of 1
to 4.6
, with the longest length coming on the 29th. His measurements of the tail angle revealed that it decreased from PA 230
to PA 69
. C. E. Spratt (Victoria, British Columbia, Canada) followed the comet using 11  80 binoculars from the 4th to the 28th. He gave tail lengths of 0.5
to 3.5
, with the longest coming on the 27th. Spratt reported that the tail angle decreased from PA 215
to PA 90
. The comet reached a maximum elongation of 156
on August 20. Bortle made numerous observations of the coma using his 32-cm reflector, which are too extensive to include here; however, he consistently reported a stellar to near-stellar nucleus and noted changes in the condensation surrounding the nucleus that indicated possible outbursts. On August 16, he noted, “suggestions of large, very vague structures in the coma at lowest powers . . ..” The comet moved southward during September and remained moderately condensed. Although it was still heading toward perihelion, its distance from Earth was increasing, which caused it to slowly fade. Most interesting is the fact that the number of observations reported to the International Comet Quarterly was only about a tenth of that reported in August. Seargent was the most prolific naked-eye observer, as he detected it on 11 nights spanning the 6th to the 20th, reporting that the magnitude faded from about 4.0 to 4.8. The final naked-eye observation was made by V. F. de Assis Neto (Sao Francisco de Oliveira, Brazil) on September 20.99, when he judged the magnitude as 5.4. P. Camilleri (Cobram, Victoria, Australia) mostly observed the comet using 20  80 binoculars from the 7th to the 22nd, noting the coma diameter generally decreased from 100 to 40 . He also reported that the tail length varied from 1.5
to 5
, while the tail generally rotated from PA 70
to 80
. Camilleri noted that the tail curved toward the north on the 9th and 10th. A. F. A. L. Jones (Nelson, New Zealand) observed the comet from the 1st to the 27th using 7  50 binoculars. He said the coma diameter varied from 70 to 130 . Jones also reported that the tail length varied from 0.4
to 1.25
, with the tail generally rotating from PA 75
to 110
. The comet was only visible to Southern Hemisphere observers in October and was generally described as strongly condensed. It was fading at a very slow rate. J. G. de Souza Aguiar (Campinas, Sao Paulo, Brazil) followed the 504

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comet on ten nights from the 2nd to the 25th using 20  50 binoculars. He indicated that it faded from 5.6 to 6.2, while the coma diameter generally decreased from 150 to 80 . Seargent saw the comet on nine nights from the 7th to the 20th, using a variety of binoculars. He indicated that the comet faded from 5.6 to 6.0, while the coma was 2–30 across. Pearce saw the comet on six nights spanning the 8th to the 22nd. Using 20  80 binoculars, he said it faded from 5.9 to 6.0, while the coma diameter generally decreased from 40 to 2.40 . Pearce also reported a tail, indicating that the length generally decreased from 1.1
to 0.33
, while the PA varied from 119
to 122
. Camilleri also followed the comet with 20  80 binoculars. From the 6th to the 28th, he indicated tail lengths of 0.8
to 3.5
and said the tail rotated from PA 90
to PA 100
. Only a few visual observations were reported in November, as the comet passed just 24
from the Sun on the 10th. Jones saw the comet using his 32-cm reflector on the 13th and determined the magnitude as 8.0. On the 23rd, Seargent estimated the magnitude as 6.4 and the coma diameter as 30 in 15  80 binoculars. He also noted a faint, fan-shaped tail in PA 230
. Garradd observed the comet on the 25th, using 10  50 binoculars. He determined the brightness as 6.2. Pearce observed the comet on the 26th and 28th, using 20  80 binoculars. He estimated the comet’s magnitude as 6.5 on both nights and the coma diameter as 30 and 3.80 , respectively. On the second night, he noted a 90 long tail in PA 233
. Another observation by Pearce on the 29th revealed a magnitude as 6.6 and a coma diameter as 3.50 . The comet had moved far enough from the Sun in December to enable observers in both the Northern and Southern Hemispheres to see it again. Following interference from moonlight, Hale located the comet with his 20-cm reflector on the 10th, estimating the magnitude as 7.5. The comet attained its most southerly declination of 41
on December 11. That same night, Seargent determined the magnitude as 7.0 while using 15  80 binoculars. Switching to his 25-cm reflector, Seargent said the coma was 2.00 across, while the tail extended 180 in PA 250
. On the 14th, Camilleri observed the comet with 20  80 binoculars, estimating the magnitude as 7.7 and the diameter as 2.00 . He added that the tail extended 450 in PA 255
. Pearce followed the comet using 20  80 binoculars, giving the magnitude as 7.4–7.5 during the 22nd to the 28th. He indicated that the coma diameter varied from 3.2–4.00 and remained moderately condensed. Pearce added that the tail extended 30 in PA 276
on the 22nd. Camilleri observed the comet with his 20-cm reflector on December 24, giving the magnitude as 7.6. He added that the coma was 1.50 across, while the tail extended 450 in PA 280
. More observations were reported in 1991 January than during the previous month, with most observers reporting a moderately condensed coma. Jones gave the magnitude as 7.2 while using his 5-cm refractor on the 5th. Hale saw the comet on the 7th and 11th, using 10  50 binoculars, and gave the magnitude as 7.6 on both nights. Camilleri obtained 15-minute 505

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exposures of the comet on the 10th and 12th, using Kodak Technical Pan 2415 film and a 200-mm telephoto lens. For the first night, he noted a very strongly condensed coma, with a main tail extending 300 in PA 315
and an anti-tail extending 450 in PA 225
. For the second night, he said the comet was unchanged, except that the main tail extended toward PA 280
and the antitail extended 1.0
in PA 210
. Morris saw the comet with 20  80 binoculars on the 13th, judging the magnitude as 7.0 and the coma diameter as 7.50 . He added that the tail extended 300 in PA 285
. On the 19th, Morris determined the magnitude as 7.1 and the coma diameter as 50 . He added that tails extended 450 in PA 305
and 45’ in PA 145
. Morris also observed with his 26-cm reflector and said the main tail was almost invisible, while “a fan that began at the edge of the anti-tail . . . wrapped around toward PA 180
.” Seargent determined the magnitude as 6.8 on the 21st, using 15  80 binoculars, and noted a broad, faint tail extending about 0.5
in about PA 235
. Using 10  50 binoculars, Hale gave the magnitude as 7.6 on the 24th. A. Nakamura (Kuma, Ehime, Japan) observed the comet on the 26th, using his 20-cm reflector. He determined the magnitude as 7.4 and the coma diameter as 70 . Nakamura also reported a tail extending 300 in PA 145
. In spite of the fact that the comet was slowly fading, more than twice as many observations were reported in February than in the previous month. On the 4th, Seargent estimated the 80 coma as magnitude 7.3 with 10  50 binoculars. Camilleri saw the comet on the 5th, 6th, and 7th, using 20  80 binoculars. He judged the magnitude as 7.0 and reported the coma diameter as 3–3.50 . Camilleri added that the tail extended 1.5
in PA 180
on each night, although he also noted “traces of a tail” in PA 305
on the 6th. Morris said his 20  80 binoculars revealed the magnitude as 7.1 on the 9th, while the moderately condensed coma was 7.50 across. He reported two tails that were 200 long and extended toward PA 140
and PA 320
. Camilleri determined the magnitude as 6.9 on the 14th. He also noted a moderately condensed coma that was 40 across and a tail extending 1
in PA 195
. Seargent observed with his 15  80 binoculars on the 19th and gave the magnitude as 7.1. Hale said it was 7.8 on the 22nd. The comet reached a maximum elongation of 153
on February 24. The number of reported observations increased again in March. The consensus of all observers indicates that the comet faded and the coma became more diffuse; however, the rate of fading seems to differ, even among experienced observers. Bortle saw the comet on seven nights from the 6th to the 21st, using 20  80 binoculars. He indicated the magnitude slowly faded from 8.1 on the 6th to 8.3 by the 17th, but then dropped to 8.6 by the 21st. Seargent also observed the comet on seven nights, but spanning the period of the 3rd to the 17th. He used 15  80 binoculars from the 3rd to the 13th and said the magnitude faded from 7.6 to 9.5. Seargent also observed with his 15-cm reflector on the 13th and determined the magnitude as 9.7. The same instrument revealed a magnitude of 9.8 on the 17th. R. J. Modic (Ohio, USA) observed the comet on nine nights from the 506

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5th to the 21st, using his 20-cm reflector. He indicated that the comet’s brightness generally faded, giving the magnitude as 8.9 on the 5th and 9.8 on the 21st. Bortle and Modic made several estimates of the coma diameter, but they were inconclusive as to whether the coma was increasing or decreasing in diameter. Bortle indicated that the coma diameter varied from 5.10 to 7.20 and Modic indicated that it varied from 2.20 to 4.00 . Bortle’s 32-cm reflector revealed a possible tail on the 6th and 9th that was pointing toward PA 150
. Modic saw a tail on the 12th, using his 40-cm reflector, and noted that it extended 60 in PA 145
. He next saw the tail on the 16th, using his 20-cm reflector, and noted that it extended 20 in PA 135
. Less than half as many observations were reported in April than in the previous month, as the comet continued to fade. The coma was generally described as slightly condensed. Hale used his 41-cm reflector to observe the comet on the 2nd, giving the magnitude as 9.8. Bouma observed with his 25-cm reflector on the 3rd and judged the magnitude as 10.1. He added that the coma was 2.50 across. Using his 26-cm reflector on the 6th, Morris set the magnitude at 10.2. He noted a coma diameter of 3.40 and said the tail extended 6.60 in PA 195
. Hale’s observation on the 9th revealed a magnitude of 10.1. Bouma gave the magnitude as 10.8 on the 11th, while the coma was still 2.50 across. Morris likewise judged the magnitude as 10.8 on the 13th, but found the coma to be somewhat larger, at 3.30 . Using a 51-cm reflector on the 14th, Morris detected a tail extending 30 in PA 160
. Pearce observed with his 41-cm reflector on the 17th, giving the magnitude as 12.1 and the coma diameter as 1.30 . Modic saw the comet with his 20-cm reflector on the 18th and determined the magnitude as 12.0, while the coma was also 1.30 across. Following interference from moonlight, Nakamura saw the comet on the 30th, using his 20-cm reflector. He judged the magnitude as 12.1 and the coma diameter as 2.00 . Only a few visual observations were reported in May, with the coma still being described as slightly condensed. Hale gave the magnitude as 11.4 on the 2nd and Nakamura gave it as 12.7 on the 3rd. The latter observer said the coma was 1.50 across. Modic saw a much smaller coma on the 11th and 12th, estimating it as 0.5–0.60 across, which is probably the reason that he gave a much fainter magnitude of 13.5–13.6. Morris noted a coma 2.20 across on the 12th and determined the magnitude as 11.8. Bortle saw the comet on the 17th while using his 50-cm reflector. He gave the magnitude as 12.5 and the coma diameter as 0.90 . Hale searched for the comet on the 30th and 31st, but was unsuccessful. He suggested the comet was fainter than magnitude 12.5. Morris made the final visual observations of this comet in early June. Using a 51-cm reflector, he determined the magnitude as 13.5 on the 2nd and 13.6 on the 8th. The coma was described as slightly condensed, with a diameter of 1.00 on the first night and 4900 on the second night. The comet reached a minimum elongation of 3
on August 8 and as a result was lost in the Sun’s glare for a few months. Hale tried to observe the 507

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comet on October 14 with his 41-cm reflector, but was unsuccessful. He noted interference from twilight and suggested the comet was fainter than 13.0. Hale made another attempt with the same telescope on November 7, but was again unsuccessful. He suggested the comet was then fainter than 13.5. The only successful observations made during the remainder of the year came from astronomers at Oak Ridge Observatory (Massachusetts, USA), when they acquired CCD images of the comet on November 3 and 6, using the 155-cm reflector. No physical descriptions were provided. Oak Ridge Observatory provided the only observations in 1992. R. E. McCrosky and C.-Y. Shao used the 155-cm reflector to acquire CCD images on January 1, 6, 8, and February 5 and 7. No physical descriptions were provided. The comet reached a maximum elongation of 166
on January 29. The comet was last detected during 1992 April 1.07–1.11, when C.-Y. Shao (Oak Ridge Observatory, Massachusetts, USA) acquired two CCD images with the 155-cm reflector. No descriptive information was provided. The position was α = 8h 16.9m, δ = +33
480 (2000). The earliest spectroscopic observations were made by K. B. Kwitter and A. Kagan (Kitt Peak National Observatory, Arizona, USA) while using the 229-cm reflector and a CCD camera on 1990 June 2 and 3. They reported the detection of cyanogen. D. G. Schleicher, D. J. Osip, T. J. Kreidl, and L. M. Sauter (Lowell Observatory, Anderson Mesa Station, Arizona, USA) observed the comet using the 107-cm Ritchey-Chretien telescope on June 3, 4, and 5. They detected the hydroxyl radical, cyanogen, diatomic carbon, triatomic carbon, and the imidyl radical. Additional observations in the following months by other observers revealed carbon monoxide, carbon monosulfide, hydrogen cyanide, formaldehyde, methanol, and hydrogen sulfide. P. D. Feldman et al. (1991) reported observations that were made with the Hopkins Ultraviolet Telescope (HUT) during the Astro-1 mission of the space shuttle Columbia. The comet was seen for 20 minutes on 1990 December 10 and was the final target of the mission. HUT revealed “the presence of carbon monoxide and atomic hydrogen, carbon, and sulfur in the coma.” The first parabolic orbit was calculated by D. W. E. Green and was published on 1990 May 26. He used 10 positions from May 21–26 and determined the perihelion date as 1990 November 10.79. Revisions were published by Green on June 7 and B. G. Marsden on July 8, which gave the perihelion date as October 24.36 and October 24.91, respectively. The first hyperbolic orbit was calculated by Marsden and was published on August 6. This used 79 positions from May 21 to July 20 and included perturbations by all nine planets. The result was a perihelion date of October 24.63 and an eccentricity of 1.00127. As further observations were reported, S. Nakano calculated revised hyperbolic orbits that were published on 1990 September 1, December 2, and 1991 January 30. These ultimately established the perihelion date as October 24.68 and the eccentricity as 1.00043. Marsden took Nakano’s orbit 508

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from September 1 and determined that the original orbit was elliptical with a period of about 151 thousand years, while the future orbit is hyperbolic with an eccentricity of 1.00049. Marsden said “This is not a ‘new’ comet in the Oort sense.” The last two orbits included solutions for nongravitational effects, with Nakano giving the terms as A1 = +2.85 and A2 = +0.4453 on December 2 and A1 = +3.57 and A2 = +0.4473 on January 30. B. G. Marsden (1992) took 314 positions from the entire period of visibility, included perturbations by all nine planets, and solved for nongravitational effects. The result was a perihelion date of October 24.68 and an eccentricity of 1.00042. The nongravitational terms were given as A1 = +3.03 and A2 = 0.2153. This orbit is given below. T ω Ω (2000.0) i q e 1990 Oct. 24.6837 (TT) 242.6656 139.3647 131.5829 0.938705 1.000417

absolute magnitude: H0 = 4.5, n = 2.8 (Shanklin, 1996) full moon: May 9, Jun. 8, Jul. 8, Aug. 6, Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30, Apr. 28, May 28, Jun. 27, Jul. 26, Aug. 25, Sep. 23, Oct. 23, Nov. 21, Dec. 21, 1992 Jan. 19, Feb. 18, Mar. 18, Apr. 17 sources: D. H. Levy, A. Hale, and C. S. Morris, IAUC, No. 5017 (1990 May 21); T. Seki and D. W. E. Green, IAUC, No. 5023 (1990 May 26); K. B. Kwitter and A. Kagan, IAUC, No. 5028 (1990 Jun. 4); D. G. Schleicher, D. J. Osip, T. J. Kreidl, and L. M. Sauter, IAUC, No. 5029 (1990 Jun. 7); D. W. E. Green, IAUC, No. 5030 (1990 Jun. 7); A. Hale, C. S. Morris, and A. R. Pearce, ICQ, 12 (1990 Jul.), p. 101; T. Seki and B. G. Marsden, MPC, Nos. 16483, 16552 (1990 Jul. 8); B. G. Marsden, IAUC, No. 5060 (1990 Jul. 25); B. G. Marsden, MPC, No. 16684 (1990 Aug. 6); S. Nakano and B. G. Marsden, IAUC, No. 5085 (1990 Sep. 1); S. Nakano, MPC, No. 16841 (1990 Sep. 5); R. J. Bouma, A. R. Pearce, R. J. Modic, D. A. J. Seargent, A. Hale, J. E. Bortle, A. F. A. L. Jones, and V. F. de Assis Neto, ICQ, 12 (1990 Oct.), pp. 115–16, 142–61; S. Nakano, MPC, No. 17401 (1990 Dec. 2); C. S. Morris, R. Haver, S. Garro, C. E. Spratt, D. A. J. Seargent, P. Camilleri, A. F. A. L. Jones, A. R. Pearce, and A. Hale, ICQ, 13 (1991 Jan.), pp. 5–6, 27–56; S. Nakano, MPC, No. 17596 (1991 Jan. 30); R. J. Modic, P. Camilleri, D. A. J. Seargent, A. Hale, C. S. Morris, and J. E. Bortle, ICQ, 13 (1991 Apr.), pp. 70–1, 76–8; D. H. Levy, J. Jahn, A. Hale, A. Nakamura, P. Camilleri, D. A. J. Seargent, J. E. Bortle, R. J. Modic, and A. R. Pearce, ICQ, 13 (1991 Jul.), pp. 95, 118–27; P. D. Feldman, A. F. Davidsen, W. P. Blair, C. W. Bowers, W. V. Dixon, S. T. Durrance, H. C. Ferguson, R. C. Henry, R. A. Kimble, G. A. Kriss, J. W. Kruk, K. S. Long, H. W. Moos, O. Vancura, and T. R. Gull, APJ, 379 (1991 Sep. 20), pp. L37–40; G. J. Garradd, C. S. Morris, A. Hale, and A. F. A. L. Jones, ICQ, 13 (1991 Oct.), pp. 156–61; P. Camilleri, ICQ, 14 (1992 Jan.), p. 5; [Oak Ridge], MPC, No. 19360 (1992 Jan. 19); R. E. McCrosky and C.-Y. Shao, MPC, No. 19560 (1992 Feb. 18); R. E. McCrosky 509

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and C.-Y. Shao, MPC, No. 19727 (1992 Mar. 18); B. G. Marsden, MPC, No. 20602 (1992 Aug. 13); B. S. Rautela and B. B. Sanwal, EM&P, 58 (1992 Sep.), pp. 233-5; J. G. de Souza Aguiar, ICQ, 15 (1993 Oct.), pp. 158–60; R. J. Bouma, ICQ, 16 (1994 Apr.), pp. 40–2; P. Schmeer, ICQ, 16 (1994 Jul.), pp. 90–2; J. D. Shanklin, JBAA, 105 (1995), pp. 295–300; A. R. Pearce, ICQ, 17 (1995 Jul.), pp. 136–40; J. D. Shanklin, JBAA, 106 (1996 Apr.), pp. 87, 89; D. H. Levy and S. M. Larson, David Levy’s Guide to Observing and Discovering Comets. Cambridge (UK): Cambridge University Press (2003), pp. 55–6. 80P/Peters– Recovered: 1990 May 26.44 (Δ = 0.87 AU, r = 1.65 AU, Elong. = 123
) Hartley Last seen: 1990 August 25.84 (Δ = 1.52 AU, r = 1.75 AU, Elong. = 85
) Closest to the Earth: 1990 May 24 (0.8691 AU) 1990 IX=1990d Calculated path: CEN (Rec), HYA (Jun. 3), VIR (Jul. 8), LIB (Jul. 22) S. Nakano (1987) took 19 positions from the 1982 apparition, applied full planetary perturbations, and integrated the orbit to this apparition. He predicted the comet would pass perihelion on 1990 June 21.60. This comet was recovered by R. H. McNaught (Siding Spring Observatory, New South Wales, Australia) when he acquired a 15-minute exposure using the 51-cm Uppsala Southern Schmidt telescope on 1990 May 26.44. He estimated the magnitude as 14 and noted the coma was diffuse. The position was α = 11h 54.0m, δ = 39
130 (2000). The comet’s appearance was unchanged on a 10-minute exposure that McNaught obtained on May 29.60. The comet had actually been looked for by A. R. Pearce (Australia) on April 17.54, using his 41-cm reflector, but no trace was found. He concluded that it must have been fainter than magnitude 13.5. An ephemeris published by the International Comet Quarterly (ICQ) in 1989 July, predicted that the comet’s magnitude would have been about 14.9–15.0 at the time of McNaught’s recovery and about 15.5 at the time of Pearce’s search. The first visual observations were made by P. Camilleri (Cobram, Victoria, Australia) on May 27 and May 29, following a communication from D. A. J. Seargent (The Entrance, New South Wales, Australia) stating that McNaught had found the comet. Camilleri was using his 20-cm reflector and described the comet as moderately condensed, 3–40 across, and about magnitude 13. This indicates that the comet was roughly two magnitudes brighter than the ICQ prediction and had probably been barely missed by Pearce. Following interference by moonlight, T. Seki (Geisei, Kochi, Japan) photographed the comet on June 11, using his 60-cm reflector. He estimated the magnitude as 15. Pearce visually observed the comet on the 15th. He judged the magnitude as 13.2 and noted an uncondensed coma 1.00 across. A. Hale (Las Cruces, New Mexico, USA) saw the comet using his 41-cm reflector on the 16th and estimated the magnitude as 12.8. The comet was seen by Hale, Camilleri, and C. S. Morris (Pine Mountain Club, California, USA) on the 17th. Hale gave the magnitude as 12.6 and said the coma was 510

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very slightly condensed. Camilleri determined the magnitude as 12.8 and said the coma was slightly condensed and 40 across. Morris was using his 51-cm reflector and noted a much brighter magnitude of 11.2. He added that the coma was very slightly condensed and 3.20 across. Morris made two more observations on the 23rd and 24th, giving the magnitude as 11.3 and 11.2, respectively. He said the coma was uncondensed and 3.0–3.10 across. Pearce observed the comet on the 24th, 25th, and 26th. He gave the magnitude as 12.9–13.0 and noted a very slightly condensed coma 1.1–1.40 across. Only a few observations were made in July. Hale described the comet as “very vague and diffuse” on the 13th, giving the magnitude as 13.0. He indicated that it was “definitely enhanced” when viewed through a filter that blocked almost all light except that of diatomic carbon. Morris judged the magnitude as 11.0 and 11.4 on the 14th and 15th, respectively. Seki photographed the comet on the 19th and estimated the magnitude as 15. The final astrometric positions were obtained on July 20.37 and July 20.39, when A. C. Gilmore and P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) acquired two 30-minute exposures using a 61-cm reflector. They estimated the magnitude as 16. The position on the final photograph was α = 14h 15.7m, δ = 18
020 (2000). The comet was last detected on August 21.85, August 24.85, and August 25.84 by R. J. Bouma (Netherlands). He was visiting Puimichel Observatory (France) and made his observations using the 106-cm reflector, which was built by D. Cardoen and was then the largest amateur-owned telescope in the world. Bouma described the comet as totally diffuse, giving the magnitude as 13.8 on the 21st, and 14.0 on both the 24th and 25th. He noted the coma diameter as 0.70 on the first night and 0.80 on the last night. Multiple apparition orbits have been calculated by D. W. E. Green (1990), Nakano (1991), P. Rocher (1998), B. G. Marsden (1999), and K. Kinoshita (2000). All of these calculations included full planetary perturbations, while only those published from 1998 onward solved for nongravitational effects. The general result was a perihelion date of June 23.64 and a period of 8.13 years. The nongravitational terms were within the following ranges: A1 = +0.31 to +1.06 and A2 = 0.0793 to 0.0687. The orbit of Kinoshita (2000) is given below. T ω Ω (2000.0) i q e 1990 Jun. 23.6354 (TT) 338.3010 260.1041 29.8339 1.625750 0.597922

absolute magnitude: H0 = 8.1/9.7, n = 6, from visual observations (Meyer) full moon: May 9, Jun. 8, Jul. 8, Aug. 6, Sep. 5 sources: S. Nakano, MPC, No. 12128 (1987 Aug. 9); S. Nakano, Nakano Note, No. 503 (1987 Aug. 20); S. Nakano, ICQ, 11 (1989 Jul.), p. H29; R. H. McNaught, D. W. E. Green, and P. Camilleri, IAUC, No. 5026 (1990 511

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May 29); R. H. McNaught, MPC, No. 16484 (1990 Jul. 8); A. R. Pearce, C. S. Morris, and A. Hale, IAUC, No. 5061 (1990 Jul. 26); T. Seki, MPC, No. 16775 (1990 Sep. 5); A. R. Pearce, P. Camilleri, and A. Hale, ICQ, 12 (1990 Oct.), pp. 118, 167–8; T. Seki, MPC, No. 17087 (1990 Nov. 2); C. S. Morris, ICQ, 13 (1991 Jan.), p. 61; A. C. Gilmore and P. M. Kilmartin, MPC, No. 17684 (1991 Feb. 28); S. Nakano, Nakano Note, No. 550 (1991 Aug. 4); R. J. Bouma, ICQ, 16 (1994 Apr.), p. 73; P. Rocher correspondence with G. W. Kronk (1998); B. G. Marsden, CCO, 13th ed. (1999), pp. 74–5; K. Kinoshita correspondence with G. W. Kronk (2000, 2014); S. Nakano, Nakano Note, No. 940 (2003 Apr. 20); P. M. Kilmartin correspondence with G. W. Kronk (2011); R. H. McNaught correspondence with G. W. Kronk (2011); S. Nakano, Nakano Note, No. 2075 (2011 May 6); R. J. Bouma correspondence with D. A. J. Seargent (2014); R. J. Bouma correspondence with G. W. Kronk (2015); P. Camilleri correspondence with D. A. J. Seargent (2014). 43P/Wolf– Recovered: 1990 June 14.38 (Δ = 2.29 AU, r = 2.81 AU, Elong. = 111
) Harrington Last seen: 1992 February 5.39 (Δ = 2.68 AU, r = 3.05 AU, Elong. = 103
) Closest to the Earth: 1990 October 13 (1.4344 AU) 1991 V=1990e Calculated path: PEG (Rec), PSC (1991 Jan. 15), ARI (Feb. 24), TAU (Mar. 30), ORI (May 19), GEM (May 30), CMi (Jun. 22), CNC (Jul. 2), HYA (Jul. 23), SEX (Aug. 17), CRT (Sep. 21), CRV (Oct. 30), HYA (Dec. 12) The only published prediction for the return of this comet came from S. Szutowicz (1987, 1988, 1990). He used 73 positions obtained from 1971–1985, included planetary perturbations, and solved for nongravitational effects. It was predicted that the comet would pass perihelion on 1991 April 4.83. The comet was recovered during 1990 June 14.38–14.43, when J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired four CCD images using the 91-cm reflector. He gave the magnitude as 19.3 and noted a tail extending 1000 in PA 250
. The position on the first image was α = 23h 06.8m, δ = +15
120 (2000). Scotti acquired two additional images during June 15.44–15.45. The only observations reported for July came from T. Seki (Geisei, Kochi, Japan). He photographed the comet using his 60-cm reflector and estimated the magnitude as 19 on the 20th and 18.5 on both the 30th and 31st. The comet was not observed during the next three months, even though it was well placed for Northern Hemisphere observatories. It attained its most northerly declination of +26
on September 3 and reached a maximum elongation of 150
on September 16. C. S. Morris (California, USA) tried to see the comet using his 51-cm reflector on September 16 and October 14, but was unsuccessful. He suggested the comet was then fainter than magnitude 13.8 on the first night and 13.5 on the second night. A. Hale (Las Cruces, New Mexico, USA) tried to see the comet using his 41-cm reflector on September 27 and October 13, but was unsuccessful. He suggested the 512

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comet was probably fainter than magnitude 13.5 on the first night and 13.0 on the second night. The next observations were made in November. T. Kojima (Chiyoda, Gunma, Japan) obtained photographs with his 25-cm reflector on the 10th and 12th, estimating the magnitude as 14.5 and 14, respectively. Astronomers at Oak Ridge Observatory (Massachusetts, USA) obtained CCD images on the 14th, 16th, and 20th, but provided no physical descriptions. Hale examined the comet’s predicted position on the 9th, but failed to see it. He suggested the comet was probably fainter than magnitude 13.5. R. J. Modic (Ohio, USA) tried to observe the comet with his 36-cm reflector on November 15, but was unsuccessful. He suggested the comet was probably fainter than magnitude 13.0. The comet was finally visually observed in December. Modic spotted it on the 8th and 12th, using his 40-cm reflector. He gave the magnitude as 13.8 and 13.6, respectively. He noted the coma was only slightly condensed and 0.6’ across. Hale saw the comet with his 41-cm reflector on the 18th, 19th, and 20th, giving the magnitude as 13.3, 13.4, and 13.3, respectively. After having moved southward since early September, the comet attained a declination of +12
on December 30 and then began a northerly motion. The first physical description reported in 1991 came from Kojima, when he estimated the photographic magnitude as 13.5 on January 6. Morris saw the comet with his 26-cm reflector on the 11th. He judged the magnitude as 13.1 and said the coma was very slightly condensed and 1.20 across. That same night, Hale determined the magnitude as 12.9. Morris next saw the comet on the 13th and 19th, giving the magnitude as 13.3 and 12.6, respectively. He noted the coma showed little condensation and was 1.60 across on the first night and 1.40 across on the second night. The comet brightened only slightly in February and observations revealed very little condensation within the coma. R. J. Bouma (Groningen, Netherlands) saw the comet with his 25-cm reflector on the 2nd and 4th, giving the magnitude as 13.2 and 13.0, respectively. He added that the coma was 0.50 across. Also on the 4th, Modic saw the comet with his 40-cm reflector. He judged the magnitude as 12.5 and the coma diameter as 0.80 . Hale determined the magnitude as 12.7 and 12.6, on the 5th and 17th, respectively. Morris saw the comet on the 9th and 10th. He gave the magnitude as 12.4 and the coma diameter as 2.00 on the first night and gave these values as 12.5 and 1.80 , respectively, on the second night. The final astrometric positions were obtained on March 3.44 and March 3.45, when Kojima photographed the comet using a 25-cm reflector. No descriptive information was provided. The position on the last image was α = 2h 05.3m, δ = +15
590 (2000). Several observers continued to visually follow the comet for another month and a half, generally noting a slightly condensed coma. Morris saw the comet on March 9, giving the magnitude as 12.3 and the coma diameter as 3.00 . Modic judged the magnitude as 13.3 on the 12th and reported a coma only 513

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1800 across. On March 13 and 17, Hale gave the magnitude as 12.5 and 12.6, respectively. Additional observations were made by Hale on April 2 and 4. He determined the magnitude as 12.3 on both nights. Morris determined the magnitude as 11.5 on the 13th, using his 26-cm reflector. He switched to his 51-cm reflector on the 14th and said the comet was “glimpsed” in poor seeing. Nevertheless, he reported the coma diameter as 1.40 . The final visual observations of this comet were made on April 16.47 and April 17.47 by A. R. Pearce (Scarborough, Western Australia, Australia), using his 41-cm reflector. On the first night, he gave the magnitude as 12.9 and the coma diameter as 0.90 . On the second night, he noted a magnitude of 13.1 and the coma diameter as 0.60 . After having moved northward since last December, the comet attained a declination of +18
on April 17 and then began a southerly motion. The comet reached a minimum elongation of 12
on August 23. The comet was last detected during 1992 February 4.29 and February 5.39, by astronomers at La Silla Observatory (Chile) using the 154-cm reflector. J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton (2000) analyzed these images as part of a program to study cometary nuclei. They said the comet “was very active, showing a coma and a tail,” determining the V magnitude as 20.6. They estimated the radius of the nucleus as 2.9 kilometers. The predicted position on the last night was α = 13h 32.5m, δ = 29
490 (2000). Multiple apparition orbits have been calculated by K. Muraoka (1992, 1994), S. W. Milbourn (1994), B. G. Marsden (1997), M. Królikowska, G. Sitarski, and Szutowicz (1998), Nakano (1999, 2001, 2003, 2005), P. Rocher (1999, 2004, 2006), and K. Kinoshita (2003, 2004, 2006). All of these calculations included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of April 4.82–4.83 and a period of 6.51–6.52 years. The nongravitational terms were within the following ranges for all of the above orbits except that of Królikowska, Sitarski, and Szutowicz: A1 = +0.19 to +0.39 and A2 = 0.0793 to 0.0687. Królikowska, Sitarski, and Szutowicz used the forced precession model of nongravitational motion to link all apparitions of this comet, from the discovery in 1924 through 1997. Although their results provided an excellent model of the comet’s long-term motion, their orbits produced residuals for the 1984 and 1991 apparitions that were almost twice as high as the residuals produced by the other orbits mentioned above. Therefore, the orbit of Kinoshita (2003) is given below. T ω Ω (2000.0) i q e 1991 Apr. 4.8255 (TT) 186.9530 254.8898 18.4721 1.607837 0.539049

absolute magnitude: H0 = 6.7, n = 8.0, from visual observations (Meyer) full moon: Jun. 8, Jul. 8, Aug. 6, Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30, Apr. 28 514

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sources: S. Szutowicz, AcA, 37 (1987), pp. 184, 186; S. Szutowicz, MPC, No. 13057 (1988 May 1); J. V. Scotti, IAUC, No. 5033 (1990 Jun. 15); J. V. Scotti, MPC, Nos. 16484–5 (1990 Jul. 8); S. Szutowicz, BAA Handbook for 1991 (1990 Aug.), p. 77; T. Seki, MPC, No. 16937 (1990 Oct. 4); C. S. Morris and A. Hale, ICQ, 13 (1991 Jan.), p. 61; T. Kojima and [Oak Ridge], MPC, No. 17490 (1991 Jan. 30); A. Hale and C. S. Morris, ICQ, 13 (1991 Apr.), p. 84; R. J. Modic, A. Hale, and A. R. Pearce, ICQ, 13 (1991 Jul.), p. 133; T. Kojima, MPC, No. 18493 (1991 Aug. 25); C. S. Morris, ICQ, 13 (1991 Oct.), pp. 149, 177; K. Muraoka, CCO, 7th ed. (1992), pp. 34, 68, 74; S. W. Milbourn, CCO, 9th ed. (1994), pp. 36, 71, 77; R. J. Bouma, ICQ, 16 (1994 Apr.), pp. 67–8; K. Muraoka, Nakano Note, No. 612 (1994 Apr. 24); B. G. Marsden, CCO, 12th ed. (1997), pp. 60–1; M. Królikowska, G. Sitarski, and S. Szutowicz, AcA, 48 (1998), p. 101; P. Rocher correspondence with G. W. Kronk (1999, 2004, 2006); J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton, Icarus, 147 (2000 Sep.), pp. 165, 176; S. Nakano, Nakano Note, No. 781 (2001 Apr. 26); K. Kinoshita correspondence with G. W. Kronk (2003, 2004, 2006); S. Nakano, Nakano Note, No. 992 (2003 Nov. 19); S. Nakano, Nakano Note, No. 1263 (2005 Oct. 24). 45P/Honda– Recovered: 1990 June 17.42 (Δ = 0.90 AU, r = 1.59 AU, Elong. = 113
) Mrkos– Last seen: 1990 October 13.49 (Δ = 1.50 AU, r = 0.82 AU, Elong. = 31
) Pajdusáková Closest to the Earth: 1990 July 31 (0.2890 AU) Calculated path: AQR (Rec), CET (Jul. 11), TAU (Jul. 31), ORI (Aug. 6), TAU 1990 XIV=1990f (Aug. 10), ORI (Aug. 11), GEM (Aug. 14), CNC (Aug. 27), LEO (Sep. 13) The only prediction for the return of this comet was published by S. Nakano (1987, 1989). He used 46 positions from 1969–1980, included full planetary perturbations, and solved for nongravitational effects. He then integrated the comet’s motion to this apparition and predicted a perihelion date of 1990 September 12.78. This comet was recovered by J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) on six CCD images acquired during 1990 June 17.42–17.46, using the 91-cm reflector. He described it as slightly diffuse, with a diameter of 5–600 , and about magnitude 19.5. The position on the first date was α = 22h 26.8m, δ = 13
320 (2000). Three additional images were obtained during June 18.44–18.45, with the magnitude given as 19.4. The comet was independently recovered by J. B. Gibson (Palomar Observatory, California, USA) on two CCD images acquired during June 17.43–17.44, using the 152-cm reflector and a Gunn r filter. Four CCD images on June 18.43–18.45 revealed a stellar condensation of about magnitude 21 that exhibited a coma 600 across. A possible fan-shaped tail extending 1500 toward PA 260
was faint and “right at the sky limit.” The comet reached a maximum elongation of 115
on July 1. Gibson provided the only observatory observations for July, when he acquired CCD images on the 15th, but no physical descriptions were provided. 515

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A few amateur astronomers began following the comet during the remainder of July, consistently reporting a coma devoid of condensation. A. R. Pearce (Scarborough, Western Australia, Australia) saw the comet with his 26-cm reflector on the 24th and his 41-cm reflector on the 25th. On both nights he judged the magnitude as 12.4 and said the coma was 2.50 across. Another observation by Pearce on the 27th revealed a magnitude of 12.2 and a coma diameter of 30 . C. S. Morris (Pine Mountain Club, California, USA) observed the comet on the 29th with his 26-cm reflector. He judged the magnitude as 11.2 and noted a coma 3.80 across. Pearce and A. Hale (Las Cruces, New Mexico, USA) both determined the magnitude as 11.8 on the 30th and 31st, respectively. Pearce also reported a coma 30 across. Hale remarked: “comet is very vague and diffuse; it appears as little more than a fluctuation in the background sky brightness.” The comet noticeably brightened in August, beginning the month as slightly condensed and ending the month as moderately condensed. J. E. Bortle (Stormville, New York, USA) saw the comet on the 2nd with his 32-cm reflector. He reported a coma 2.60 across that was magnitude 11.2. R. J. Bouma (Groningen, Netherlands) observed with his 25-cm reflector on the 3rd. He judged the magnitude as 11.3 and said the coma was 1.50 across. Using a 20-cm reflector on the 16th, Pearce gave the magnitude as 9.4 and said the coma was 40 across. Morris switched to 20  80 binoculars on the 19th. He determined the magnitude as 8.2 and reported a coma diameter of 50 . Hale saw the comet using his 41-cm reflector on the 24th and gave the magnitude as 8.6. Switching to 10  50 binoculars, Hale noted a magnitude of 7.8 on the 30th. Bortle saw the comet with 20  80 binoculars on the 30th and 31st, giving the magnitude as 8.3 on both nights. He reported that the coma was 2.30 across on the first night and 2.60 across on the second night. The comet was at its brightest in September, with most observers describing it as strongly condensed. Morris gave the magnitude as 8.0 and 7.8 on the 1st and 2nd, respectively. He reported that the coma was 2.50 across on the first night. Bortle gave the magnitude as 8.0 on the 4th and said the coma was 1.50 across. Another observation by Bortle on the 9th revealed a magnitude of 7.9 and a coma diameter of 1.10 . A. J. S. Pereira (Cabo da Roca, Portugal) noted a magnitude of 7.9 on the 10th, using a 15-cm reflector. He reported a coma diameter of about 1.50 . Hale and Morris saw the comet on the 17th. Hale was using 10  50 binoculars and gave the magnitude as 7.9, while Morris was using 20  80 binoculars and judged the magnitude as 8.3. An observation by Bortle on the 18th revealed a magnitude of 8.4 and a coma diameter of 20 . This same night, Bortle observed with his 32-cm reflector and suspected a narrow tail that extended about 60 in PA 310
. The last astrometric position was obtained by J. B. Tatum and D. D. Balam (Climenhaga Observatory, British Columbia, Canada) on September 21.51. The position was α = 9h 58.7m, δ = +12
070 (2000). The comet was still visually observed during the remainder of September. On the 21st, R. J. Modic (Ohio, USA) saw the comet using 516

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7  35 binoculars and gave the magnitude as 8.2. Switching to his 36-cm reflector, he noted a tail extending 30 in PA 290
. G. W. Kronk (Troy, Illinois, USA) saw the comet on the 22nd using his 33-cm reflector. He determined the magnitude as 8.4 and the coma diameter as 2.50 . Modic saw the comet with his 20-cm reflector on the 24th. He gave the magnitude as 9.0 and said the coma was 0.70 across. On the 25th, Bortle judged the magnitude as 8.7 and said the coma was 1.50 across. Hale determined the magnitude was 8.7 on the 26th. On September 28, Modic gave the magnitude as 9.6 and the coma diameter as 0.50 . The comet was last seen in October. Bortle saw it with his 32-cm reflector on the 1st. He determined the magnitude as 9.5 and said the coma was moderately condensed and 1.10 across. Modic and A. Nakamura (Kuma, Ehime, Japan) observed the comet on the 2nd. Modic gave the magnitude as 10.5 and said the coma was slightly condensed and 0.40 across. Nakamura was using his 20-cm reflector. He gave the magnitude as 9.2 and said the coma was slightly condensed and 3.00 across. The comet reached a minimum elongation of 30
on October 3. The comet was last detected on October 13.49, when Hale saw it with his 41-cm reflector and determined the magnitude as 11.0. He said he was dealing with moonlight and early twilight, so that the comet was “vague and hard to discern.” He tried to see the comet again on October 18, when it was at a low altitude, but was unsuccessful. He suggested the comet was then fainter than magnitude 12.0. At the time of this observation, the comet’s predicted position was α = 11h 23.1m, δ = +5
390 (2000). Multiple apparition orbits have been calculated by B. G. Marsden (1990), S. Nakano (1998, 2003), K. Kinoshita (1998, 2001, 2003); and P. Rocher (2001). These calculations included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of September 12.68–12.69 and a period of 5.30 years. Including positions from 1974–1990, Marsden gave the nongravitational terms as A1 = 0.40 and A2 = 0.0495. Nakano (1998) and Kinoshita (1998) used positions from 1980–1996. Nakano gave the nongravitational terms as A1 = 0.08 and A2 = 0.0669, while Kinoshita gave them as A1 = +0.02, A2 = 0.0612, and A3 = 0.11. Using positions from 1990–2001, Kinoshita (2001) gave the terms as A1=+0.20, A2 = 0.0555, and A3 = 0.10. Also using positions from 1990–2001, Rocher (2001), Kinoshita (2003), and Nakano (2003) calculated terms within the following ranges: A1 = +0.21 to +0.30 and A2 = 0.0555 to 0.0553. Rocher’s orbit is given below. T ω Ω (2000.0) i q e 1990 Sep. 12.6834 (TT) 325.7854 89.3089 4.2198 0.541252 0.821871

absolute magnitude: H0 = 13.3, n=8.0 (Shanklin, 1996); H0 = 13.91, n = 9.0 (Milani, 1996) full moon: Jun. 8, Jul. 8, Aug. 6, Sep. 5, Oct. 4, Nov. 2 517

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sources: S. Nakano, MPC, No. 12128 (1987 Aug. 9); S. Nakano, BAA Handbook for 1990 (1989), p. 75; J. V. Scotti and B. G. Marsden, IAUC, No. 5035 (1990 Jun. 19); J. B. Gibson, IAUC, No. 5046 (1990 Jul. 2); A. R. Pearce, IAUC, No. 5059 (1990 Jul. 25); A. R. Pearce, IAUC, No. 5063 (1990 Jul. 28); J. B. Gibson, MPC, No. 16656 (1990 Aug. 6); C. S. Morris and J. E. Bortle, IAUC, No. 5072 (1990 Aug. 7); A. R. Pearce and C. S. Morris, IAUC, No. 5076 (1990 Aug. 18); C. S. Morris and A. Hale, IAUC, No. 5082 (1990 Aug. 30); J. E. Bortle, C. S. Morris, and A. J. S. Pereira, IAUC, No. 5092 (1990 Sep. 18); J. E. Bortle and A. Hale, IAUC, No. 5105 (1990 Sep. 28); A. R. Pearce, A. Hale, J. E. Bortle, A. J. S. Pereira, and R. J. Modic, ICQ, 12 (1990 Oct.), pp. 118, 164; C. S. Morris, ICQ, 13 (1991 Jan.), pp. 59–60; A. Hale and R. J. Modic, ICQ, 13 (1991 Apr.), pp. 72, 81; A. Nakamura, ICQ, 13 (1991 Oct.), p. 165; G. W. Kronk, ICQ, 15 (1993 Jan.), p. 29; R. J. Bouma, ICQ, 16 (1994 Apr.), p. 60; J. D. Shanklin, JBAA, 106 (1996 Apr.), p. 89; G. Milani, ICQ, 18 (1996 Jul.), pp. 106–9; K. Kinoshita correspondence with G. W. Kronk (1998, 2001, 2003); S. Nakano, Nakano Note, No. 673 (1998 Apr. 30); P. Rocher correspondence with G. W. Kronk (2001); S. Nakano, Nakano Note, No. 936 (2003 Apr. 19). C/1990 M1 Discovered: 1990 June 19.55 (Δ = 2.90 AU, r = 3.72 AU, Elong. = 138
) (McNaught– Last seen: 1991 June 14.10 (Δ = 2.77 AU, r = 2.90 AU, Elong. = 87
) Hughes) Closest to the Earth: 1991 April 13 (1.8526 AU) Calculated path: PAV (Disc), ARA (Jun. 19), TrA (Jul. 2), NOR (Jul. 10), LUP 1991 III=1990g (Aug. 1), LIB (Oct. 25), SCO (Nov. 21), OPH (1991 Feb. 22), SER (Mar. 5), BOO (Apr. 8), CVn (May 1), This comet was discovered at Siding Spring Observatory (New South Wales, Australia), when R. H. McNaught noticed it on an R plate exposed on 1990 June 19.55 by S. M. Hughes for the Anglo-Australian Near Earth Asteroid Survey. Hughes was using the 122-cm Schmidt telescope and the exposure time was 53 minutes. Although there was cloud interference, McNaught estimated the magnitude as 17 and noted a moderately condensed coma 500 across. The comet’s position was α = 17h 43.9m, δ = 65
330 (2000). McNaught obtained a confirmation on June 20.62, when he photographed the comet using the 51-cm Uppsala Southern Schmidt telescope. The comet reached a maximum elongation of 138
on June 21. It was photographed by McNaught using the 51-cm Uppsala Southern Schmidt telescope on several occasions spanning June 21 to September 8. McNaught said a photograph obtained on June 29 revealed a possible tail extending 0.40 in PA 100
. A. C. Gilmore and P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) photographed the comet on June 23 and July 20, noting a magnitude of 17.2 on the latter date. No further observations were acquired during the remainder of 1990, as the comet’s

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elongation from the Sun decreased. The comet reached a minimum elongation of 6
on November 24. The first observation reported in 1991 came from T. Kojima (Chiyoda, Gunma, Japan) on January 22, when he photographed the comet in the southeastern morning sky using his 25-cm reflector. He estimated the magnitude as 15. A few observatories provided physical descriptions during the next few weeks. Astronomers at Siding Spring Observatory estimated the magnitude as 16 on January 27, 15.5 on February 12, and 15.5 on March 20. They added that the image acquired on February 12 revealed a strongly condensed coma 30 across that extended toward the southeast, while the image on March 20 showed a moderately condensed coma. T. Seki (Geisei, Kochi, Japan) photographed the comet on March 16 and 17, estimating the magnitude as 17. The first visual observation was made on March 15, when A. Hale (Las Cruces, New Mexico, USA) located the comet using his 41-cm reflector. He gave the magnitude as 13.4. The comet was most favorable in April, not only reaching its smallest distance from Earth on the 13th, but also reaching a maximum elongation of 144
on the 15th. Visual observers generally described the coma as slightly condensed. Hale located the comet on the 6th and gave the magnitude as 13.5. R. J. Modic (Richmond Heights, Ohio, USA) observed with his 40-cm reflector on the 11th and determined the comet’s magnitude as 13.4. He added that the coma was 0.60 across. The comet’s magnitude was given as 13.3 by Hale on the 14th and Modic on the 18th. Modic added that the coma was 1.00 across. A. R. Pearce (Scarborough, Western Australia, Australia) detected the comet with his 41-cm reflector on the 21st and gave the magnitude as 13.5. He noted the coma was 0.8’ across. On the 23rd, the magnitude was given as 13.1 by Modic and 13.5 by Pearce. Modic said the coma was 1.10 in diameter. The comet began to slowly fade in May as it moved away from both the Sun and Earth. Hale gave the magnitude as 13.3 on the 12th and 13.4 on the 19th. C. S. Morris (Lockwood Valley, California, USA) also observed the comet on the 12th. He was using his 51-cm reflector and gave the magnitude as 12.8. Morris reported a very slightly condensed coma 2.10 across. Pearce gave the magnitude as 13.5 on the 12th and 13.6 on the 16th. On the first night he noted a slightly condensed coma 0.80 across. Only one visual observation was reported in June. Using his 51-cm reflector on the 2nd, Morris determined the magnitude of the comet as 13.7 and said the slightly condensed coma was 1.00 across. Hale was not able to see the comet with his 41-cm reflector on the 7th, suggesting it was fainter than magnitude 13.5. Morris failed to locate the comet on the 8th and concluded that it must have been fainter than magnitude 14.

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The final observations of this comet were obtained on June 14.08 and June 14.10 by astronomers at Oak Ridge Observatory (Massachusetts, USA), using the 155-cm reflector and a CCD camera. No descriptive information was provided. The position on the final image was α = 12h 27.0m, δ = +37
040 (2000). The first parabolic orbit was calculated by B. G. Marsden and was published on 1990 June 25. Marsden took nine positions from June 19–23 and determined a perihelion date of 1991 March 6.45. Revised parabolic orbits were published by Marsden on August 6 and September 5, which gave the perihelion date as February 27.73 and February 27.84, respectively. The first hyperbolic orbit was calculated by Marsden and was published on 1991 March 30. He used 22 positions from 1990 June 20 to 1991 February 12 and included perturbations by all nine planets. The result was a perihelion date of February 27.67 and an eccentricity of 1.00120. An orbit by S. Nakano was published on 1991 May 28. This took 36 positions from 1990 June 20 to 1991 May 3 and included full planetary perturbations. The result was a hyperbolic orbit with a perihelion date of February 27.67 and an eccentricity of 1.00120. This orbit is given below. The 7th edition of Marsden’s Catalogue of Cometary Orbits included original and future orbits for this comet. The original orbit was elliptical with a period of about 4.0 million years, while the future orbit is hyperbolic with an eccentricity of 1.00065. K. Muraoka published an orbit on 1991 September 4. This used 45 positions from the entire apparition and included full planetary perturbations. The result was a hyperbolic orbit with a perihelion date of February 27.66 and an eccentricity of 1.00123. T ω Ω (2000.0) i q e 1991 Feb. 27.6666 (TT) 18.1719 233.2060 132.7742 2.682238 1.001198

absolute magnitude: H10 = 7.5, from visual observations (Meyer) full moon: Jun. 8, Jul. 8, Aug. 6, Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30, Apr. 28, May 28, Jun. 27 sources: R. H. McNaught and S. M. Hughes, IAUC, No. 5036 (1990 Jun. 20); R. H. McNaught and B. G. Marsden, IAUC, No. 5037 (1990 Jun. 25); R. H. McNaught, S. M. Hughes, and B. G. Marsden, MPC, Nos. 16656–7, 16684 (1990 Aug. 6); R. H. McNaught and B. G. Marsden, MPC, Nos. 16775, 16842 (1990 Sep. 5); R. H. McNaught, MPC, No. 16937 (1990 Oct. 4); A. C. Gilmore, P. M. Kilmartin, and [Siding Spring], MPC, Nos. 17684, 17688 (1991 Feb. 28); B. G. Marsden, MPC, No. 17940 (1991 Mar. 30); T. Seki and [Siding Spring], MPC, Nos. 18011–2, 18015 (1991 Apr. 28); S. Nakano, MPC, No. 18255 (1991 May 28); A. Hale and R. J. Modic, ICQ, 13 (1991 Jul.), p. 127; T. Kojima and [Oak Ridge], MPC, No. 18493 (1991 Aug. 25); K. Muraoka, Nakano Note, No. 557 (1991 Sep. 4);

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C. S. Morris, ICQ, 13 (1991 Oct.), p. 161; A. R. Pearce, ICQ, 14 (1992 Apr.), p. 37; B. G. Marsden, CCO, 7th ed. (1992), p. 97. 48P/Johnson Recovered: 1990 April 28.22 (Δ = 2.15 AU, r = 2.68 AU, Elong. = 111
) Last seen: 1991 November 11.07 (Δ = 2.26 AU, r = 3.20 AU, Elong. = 158
) 1990 Closest to the Earth: 1990 July 15 (1.4615 AU) XXIII=1990h Calculated path: SGR (Rec), CAP (Nov. 10), AQR (1991 Jan. 6), CET (Mar. 6), TAU (Jul. 6) A prediction for the return of this comet was calculated by T. Kobayashi (1987). He took 44 positions from 1963–1984, included full planetary perturbations, and solved for nongravitational effects. Integrating the motion up to this apparition revealed a likely perihelion date of 1990 November 18.96. The comet was recovered during 1990 June 17.37–17.38 and June 18.34–18.37, when J. B. Gibson (Palomar Observatory, California, USA) acquired CCD images using the 152-cm reflector and a Gunn r filter. The nuclear magnitude was estimated as 18 on the first image. The comet was described as “stellar within the limits of seeing.” The position was α = 19h 09.0m, δ = 15
110 (2000) on the first image. These positions confirmed a single-night detection on 1990 April 28.22 by astronomers at La Palma Observatory (Canary Islands) using the 256-cm Nordic Optical Telescope. J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton (2000) analyzed the La Palma images as part of a program to study cometary nuclei. They said the “comet is trailed as it was impossible to track” on it. The V magnitude was determined as 19.6. Not long after the recovery announcement by Gibson, T. Seki (Geisei, Kochi, Japan) found a trailed image of the comet on a photograph obtained with his 60-cm reflector during May 26.72–26.73. He estimated the nuclear magnitude as 19. A short time later, M. Tsumura (Oishi, Wakayama, Japan) found the comet on a photograph exposed on June 17.64. He estimated the magnitude as 18. The comet reached a maximum elongation of 174
on July 6. Only a few images were obtained during the next three months. Tsumura photographed the comet on July 25 and estimated the magnitude as 18. R. H. McNaught (Siding Spring Observatory, New South Wales, Australia) photographed the comet with the 51-cm Uppsala Southern Schmidt telescope on September 9 and 11, estimating the magnitude on each night as 17. No observations were made during the remainder of 1990. The comet attained its most southerly declination of 26
on October 19. Unsuccessful attempts to visually see the comet were made by A. Hale (Las Cruces, New Mexico, USA) and C. S. Morris (California, USA) from September to November, using reflectors of 41-cm and 51-cm aperture, indicating that it was fainter than visual magnitude 13.

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The comet drifted into twilight early in 1991 and reached a minimum elongation of 9
on March 25. After emerging from twilight, the comet attained its most northerly declination of +8
on August 11. The final astrometric positions were obtained during October 16.50–16.52, when J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired three CCD images using the 91-cm reflector. He determined the magnitude as 19.7 and reported a fan-shaped coma that extended 2000 in PA 274
to 1400 in PA 63
. The position on the last image was α = 4h 31.0m, δ = +5
120 (2000). The comet was last detected during November 11.05–11.07, when astronomers at Pic du Midi (France) acquired two CCD images using the 201-cm reflector and an R filter. Licandro, Tancredi, Lindgren, Rickman, and Hutton (2000) analyzed the images as part of a program to study cometary nuclei. They said the comet “presented a star-like appearance,” giving the R magnitude as 19.0–19.1, and determined the radius of the nucleus as 3.5 kilometers. They added, “Comet Johnson is dynamically old.” Multiple apparition orbits have been calculated by K. Muraoka (1996), P. Rocher (1999, 2004, 2005, 2006, 2015), S. Nakano (2001, 2005, 2008, 2015), and K. Kinoshita (2003, 2004, 2006, 2010). All of these calculations included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of November 18.96 and a period of 6.97 years. The nongravitational terms for all of these calculations, except Rocher (2015), were within the following ranges: A1 = +0.58 to +0.77 and A2 = 0.0265 to 0.0180. Rocher (2015) gave the terms as A1 = +0.63, A2 = 0.0186, and A3 = +0.02. The orbit of Rocher (2015) is given below. T ω Ω (2000.0) i q e 1990 Nov. 18.9570 (TT) 208.2983 117.3494 13.6611 2.312559 0.366143

absolute magnitude: H10 = 12.5 (Meyer) full moon: May 9, Jun. 8, Jul. 8, Aug. 6, Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30, Apr. 28, May 28, Jun. 27, Jul. 26, Aug. 25, Sep. 23, Oct. 23 sources: T. Kobayashi, MPC, No. 12123 (1987 Aug. 9); J. B. Gibson, IAUC, No. 5038 (1990 Jun. 26); J. B. Gibson and T. Seki, MPC, No. 16656 (1990 Aug. 6); M. Tsumura, MPC, No. 16775 (1990 Sep. 5); R. H. McNaught, MPC, No. 17087 (1990 Nov. 2); C. S. Morris, ICQ, 13 (1991 Jan.), p. 60; A. Hale, ICQ, 13 (1991 Apr.), p. 82; [Kitt Peak], MPC, Nos. 19067, 19071 (1991 Nov. 21); K. Muraoka, Nakano Note, No. 613 (1996 Apr. 11); P. Rocher correspondence with G. W. Kronk (1999, 2004, 2005, 2006, 2015); J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton, Icarus, 147 (2000 Sep.), pp. 164–5, 170; S. Nakano, Nakano Note, No. 791 (2001 Apr. 28); K. Kinoshita correspondence with G. W. Kronk (2003, 2004, 2006, 2010); S. Nakano, Nakano Note, No. 1270 (2005 Oct. 26); S. Nakano, Nakano Note,

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No. 1610 (2008 May 6); J. V. Scotti correspondence with G. W. Kronk (2011, 2015); S. Nakano, Nakano Note, No. 2870 (2015 Apr. 2). C/1990 N1 Discovered: 1990 July 13.52 (Δ = 1.73 AU, r = 1.63 AU, Elong. = 67
) (Tsuchiya– Last seen: 1991 February 10.13 (Δ = 2.42 AU, r = 2.29 AU, Elong. = 70
) Kiuchi) Closest to the Earth: 1990 December 6 (0.9389 AU) Calculated path: COM (Disc), LEO (Aug. 2), SEX (Oct. 19), HYA (Nov. 2), 1990 XVII=1990i ANT (Nov. 18), PYX (Nov. 20), PUP (Nov. 29), PIC (Dec. 13), CAE (Dec. 20), HOR (Dec. 24), ERI (Dec. 28), FOR (1991 Jan. 1), CET (Jan. 31) This comet was independently discovered by two Japanese observers. K. Tsuchiya (Toma, Hokkaido, Japan) found the comet on a survey photograph he had obtained on 1990 July 13.52. He was using an f/4 camera and Kodak T-Max film. The comet’s magnitude was estimated as 8 and Tsuchiya indicated a position of α = 12h 34.2m, δ = +30
570 (2000). T. Kiuchi (Usuda, Nagano, Japan) independently discovered the comet on July 16.51, using 25  150 binoculars. He estimated the magnitude as 9. The comet was well observed during the remainder of July. A. Hale (Las Cruces, New Mexico, USA) and C. S. Morris (Whitaker Peak, California, USA) saw the comet on the 17th. Hale was using his 41-cm reflector, but noted that sky conditions were very poor. He judged the magnitude as about 8.9 and reported a moderately condensed coma. Morris was observing with his 20  80 binoculars. He determined the magnitude as 8.9 and said the coma was slightly condensed and 8’ across. Morris found the comet unchanged on the 19th. G. J. Garradd (Tamworth, New South Wales, Australia) saw the comet with 10  50 binoculars on the 21st and gave the magnitude as 8.8. He then switched to his 25-cm reflector and noted a moderately condensed coma that was 30 across. On the 24th and 25th, P. Camilleri (Cobram, Victoria, Australia) observed with his 20  80 binoculars and determined the magnitude as 8.9. He added that the coma was slightly condensed and 5–60 across. A. R. Pearce (Scarborough, Western Australia, Australia) gave the magnitude as 8.7 on both the 27th and 28th while using 20  80 binoculars. He reported a moderately condensed coma that was 4–50 across. Also on the 28th, J. E. Bortle (Stormville, New York, USA) observed the comet with a 20-cm reflector and judged the magnitude as 8.9. He noted a slightly condensed coma that was 4.50 across. Another observation was obtained by Bortle on July 30, using his 32-cm reflector. He again determined the magnitude as 8.9 and said the coma was very slightly condensed and about 30 across. The comet’s elongation from the Sun had been decreasing since its discovery and only a few observations were obtained in August. W. C. Morrison (Ontario, Canada) observed with a 15-cm refractor on the 2nd, giving the magnitude as 9.1 and the coma diameter as 3.50 . Hale determined the magnitude as 8.6 on the 9th. Morris observed on the 11th and 12th,

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giving the magnitude as 7.9 and 7.8, respectively. He reported a slightly condensed coma 80 across on the first night and a moderately condensed coma 70 across on the second night. Hale saw the comet when it was only 26
from the Sun on August 19 and judged the magnitude as 8.3. Both Hale and Morris used atmospheric-extinction correction factors in determining their estimates due to the comet’s low elevation. The comet reached a minimum elongation of only 6
on September 12. The next observation was made on October 2, when A. Nakamura (Kuma, Ehime, Japan) saw the comet in the morning sky with his 20-cm reflector when it was less than 23
from the Sun. He determined the magnitude as 7.3 and described the coma as moderately condensed and 3.50 across. During the remainder of October, the comet changed little in brightness and observers generally noted a moderately condensed coma. Hale saw the comet on the 3rd and the 11th, giving the magnitude as 7.7. Morris also determined the magnitude as 7.7 on the 13th. The comet was seen by Pearce on the 15th while using his 20-cm reflector. He gave the magnitude as 7.3 and said the coma was 2.50 across. Using 20  80 binoculars, Bortle found the magnitude at 7.6 on the 16th and reported a coma 3.50 across. Hale switched to his 10  50 binoculars on the 17th and gave the magnitude as 7.6. An observation by Pearce on the 18th revealed a magnitude of 7.2 and a coma 40 across. On the 20th, Bortle saw the comet with his 20  120 binoculars, noting a coma 3.50 across and a tail extending 240 in PA 285
. Pearce determined the magnitude as 7.4 on the 21st and said the coma diameter was 30 . Hale judged the magnitude as 7.6 on both the 23rd and 30th. Bortle also saw the comet on the 30th. Using 10  50 binoculars, he gave the magnitude as 7.7 and the coma diameter as 6.50 . The comet faded in November, but generally remained moderately condensed. G. W. Kronk (Troy, Illinois, USA) observed the comet using 20  80 binoculars on the 6th. He judged the magnitude as 6.9 and reported a coma diameter of 30 . Also using 20  80 binoculars, Morris (Pine Mountain Club, California, USA) determined the magnitude as 7.4 and the coma diameter as 50 on the 10th, while Camilleri gave the magnitude as 7.5 and the coma diameter as 4.50 on the 12th. On the 14th, Pearce gave the magnitude as 7.3 and the coma diameter as 4.50 . Kronk determined the magnitude as 7.4 on the 17th, using his 33-cm reflector, and reported a coma 7.40 across. That same night, S. V. Zhuiko (Moscow, Russia) reported seeing a tail extending 1
in PA 295
. Camilleri observed the comet using his 20-cm reflector on the 20th. He gave the magnitude as 8.0 and noted the coma was 4.50 across. Pearce saw the comet on five nights during November 22–29. He reported that the magnitude faded from 7.7 to 8.4, while the coma diameter increased from 40 to 60 . The comet changed little in brightness during the first half of December. In addition, the comet showed only a trace of condensation throughout the month. A. Ishikawa (Japan) observed with his 13-cm reflector, noting magnitudes of 8.9 on the 4th, 8.8 on the 8th, 8.9 on the 12th, 9.0 on the 524

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16th, 8.9 on the 19th, and 9.3 on the 23rd. He added that the coma diameter was 3–40 throughout this period. D. A. J. Seargent (The Entrance, New South Wales, Australia) saw the comet with 15  80 binoculars on the 5th and judged the magnitude as 7.9. Switching to 10  50 binoculars, he reported magnitudes of 7.4 on the 7th, 7.8 on the 11th, and 7.5 on the 13th. Seargent consistently noted a coma 100 across. Pearce observed the comet with his 20  80 binoculars on 10 nights from the 10th to the 28th, noting a coma diameter of 5-80 . He gave the magnitude as 8.5 on the 10th, 8.6 on the 11th, and 8.5 on the 12th. Thereafter, the magnitude generally faded from 8.7 on the 17th to 9.0 by the 28th. The comet attained its most southerly declination of 45
on December 14 and then reached a maximum elongation of 112
on December 17. The comet continued to fade in 1991 January and displayed little or no condensation. Seargent saw it using 15  80 binoculars on the 3rd. He gave the magnitude as 9.0 and the coma diameter as about 100 . Hale (Tucson, Arizona, USA) spotted the comet with his 41-cm reflector on the 8th, giving the magnitude as 9.4. On the 10th, Camilleri determined the magnitude as 10.0 and said the coma was 20 across. Another observation by Hale on the 11th revealed a magnitude of 9.8. Morris observed the comet using his 26-cm reflector on the 13th and 19th. He judged the magnitude on both nights as 10.2 and said the coma was 2.90 across on the first night. The last astrometric positions were obtained on February 6.44 and February 6.45, when A. C. Gilmore and P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) photographed the comet using a 61-cm reflector. The exposure times were 20 and 26 minutes, respectively. The nuclear magnitude was given as 17.4 and the position on the last image was α = 2h 31.1m, δ = 22
080 (2000). Three visual observations were made following the observations of Gilmore and Kilmartin. Hale observed the comet using his 41-cm reflector on February 7.11 and gave the magnitude as 11.5. He described the comet as “very vague and diffuse; the observation was hampered by low altitude and possible cirrus.” Morris saw the comet on February 9.14 and February 10.13, using his 26-cm reflector. On both nights, he judged the magnitude as 11.5 and noted a very slightly condensed coma 2.70 across. The first parabolic orbit was calculated by D. W. E. Green and was published on 1990 July 19. This used 11 positions from July 13–19 and determined the perihelion date as 1990 September 28.65. Revised orbits were calculated by B. G. Marsden and S. Nakano, which were published on August 6 and September 5, respectively. The perihelion date was determined as September 28.69 by Marsden and September 28.60 by Nakano. The first elliptical orbit was calculated by Green and was published on October 17. This used 31 positions from July 17 to October 16 and perturbations by all nine planets. The result was a perihelion date of September 28.78 and a period of about 2015 years. As further positions were reported, Nakano calculated elliptical orbits that were published on November 2 and 525

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December 2. The first orbit revealed a perihelion date of September 28.75 and a period of about 3048 years, while the second orbit revealed a perihelion date of September 28.74 and a period of about 3637 years. Nakano calculated the last orbit for this comet. It was published on 1991 January 30. He used 54 positions from July 17 to December 24 and included full planetary perturbations. The result was a perihelion date of September 28.74 and a period of about 3562 years. This orbit is given below. The 7th edition of Marsden’s Catalogue of Cometary Orbits included original and future orbits for this comet. Both were found to be elliptical with periods of about 3111 years and 3306 years, respectively. Ω i q e (2000.0) 1990 Sep. 28.7418 (TT) 180.9189 330.7378 143.7839 1.092424 0.995316 T

ω

absolute magnitude: H0 = 5.3, n = 4.7 (Shanklin, 1996) full moon: Jul. 8, Aug. 6, Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28 sources: K. Tsuchiya and T. Kiuchi, IAUC, No. 5052 (1990 Jul. 16); C. S. Morris, IAUC, No. 5053 (1990 Jul. 17); D. W. E. Green, IAUC, No. 5055 (1990 Jul. 19); K. Tsuchiya and B. G. Marsden, MPC, Nos. 16656, 16684 (1990 Aug. 6); S. Nakano, MPC, No. 16841 (1990 Sep. 5); A. Hale, G. J. Garradd, P. Camilleri, A. R. Pearce, and J. E. Bortle, ICQ, 12 (1990 Oct.), pp. 117, 161–2; D. W. E. Green, IAUC, No. 5119 (1990 Oct. 17); S. Nakano, MPC, No. 17175 (1990 Nov. 2); S. Nakano, MPC, No. 17400 (1990 Dec. 2); C. S. Morris, A. R. Pearce, J. E. Bortle, S. V. Zhuiko, and A. Hale, ICQ, 13 (1991 Jan.), pp. 6–7, 56–8; A. Pearce, A. Hale, and C. S. Morris, IAUC, No. 5170 (1991 Jan. 18); S. Nakano, MPC, No. 17595 (1991 Jan. 30); W. C. Morrison, A. Hale, P. Camilleri, C. S. Morris, and D. A. J. Seargent, ICQ, 13 (1991 Apr.), pp. 78–9; A. C. Gilmore and P. M. Kilmartin, MPC, No. 18012 (1991 Apr. 28); A. Hale, ICQ, 13 (1991 Jul.), pp. 95, 127; A. Nakamura and A. Ishikawa, ICQ, 13 (1991 Oct.), pp. 162–3; B. G. Marsden, CCO, 7th ed. (1992), p. 96; G. W. Kronk, ICQ, 14 (1992 Oct.), p. 106; Shanklin, JBAA, 106 (1996 Apr.), p. 89; P. Camilleri, ICQ, 19 (1997 Jul.), p. 173; P. M. Kilmartin correspondence with G. W. Kronk (2011). 131P/1990 R1 Discovered: 1990 September 15.35 (Δ = 1.18 AU, r = 2.14 AU, Elong. = 155
) (Mueller 2) Last seen: 1991 February 9.99 (Δ = 2.23 AU, r = 2.17 AU, Elong. = 74
) Closest to the Earth: 1990 October 10 (1.1112 AU) 1990 XXIV=1990j Calculated path: PSC (Disc), CET (1991 Feb. 5), ARI (Feb. 8) J. E. Mueller (Palomar Observatory, California, USA) found the diffuse trail of this comet on a plate exposed by her and J. D. Mendenhall in the course of the Second Palomar Sky Survey. The plate was exposed on 1990 September 15.35–15.40 using the 122-cm Schmidt telescope. The comet 526

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was described as magnitude 17, with a tail extending toward the south-southwest. The position of the beginning of the trail was α = 0h 47.3m, δ = +12
500 (2000). H. E. Holt, H. R. Holt, C. M. Olmstead, and J. A. Brown (Palomar Observatory) confirmed the comet when they photographed it using the 46-cm Schmidt telescope on September 16.39 and September 16.43. The magnitude was given as 16.8 and they noted a “fan tail toward southwest.” The comet was observed at a few observatories during the remainder of September. Astronomers at Palomar Observatory photographed the comet on several occasions, estimating the magnitude as 17.0 on the 17th, 16.8 on the 18th, and 17.0 on the 20th. T. Seki (Geisei, Kochi, Japan) also photographed the comet on several occasions using his 60-cm reflector. He estimated the magnitude as 16–16.5 from the 19th to the 30th. Photographs were also obtained by T. Kojima (Chiyoda, Gunma, Japan) and M. Tsumura (Oishi, Wakayama, Japan) on September 20, which revealed estimated magnitudes of 16 and 15, respectively. The comet reached a maximum elongation of 174
on October 6. Only a few physical descriptions were provided in October. E. F. Helin, B. P. Roman, and K. J. Lawrence (Palomar Observatory) photographed the comet using the 46-cm Schmidt telescope on the 17th and judged the magnitude as 16.3. T. Hioki (Mizuho, Tokyo Metropolis, Japan) photographed the comet on the 26th, using a 25-cm reflector, and estimated the magnitude as 14. On that same night, Seki estimated the photographic magnitude as 17. It should be noted that A. Hale (Las Cruces, New Mexico, USA) and C. S. Morris (Lockwood Valley, California, USA) tried to visually observe the comet. Hale used his 41-cm reflector and checked the comet’s predicted position on September 26 and 27, October 13 and 26, and November 9 and 19. Nothing was detected. He suggested the comet was fainter than magnitude 13.0 on the first night and fainter than magnitude 13.5 on the other nights. Morris examined the comet’s predicted position with his 51-cm reflector on October 14, but failed to see the comet. He suggested the comet was fainter than magnitude 14.0. Although three observatories followed the comet during the remainder of the year, only one provided descriptions. Seki estimated photographic magnitudes of 17.5 on November 11 and 17.0 on December 6. The comet attained its most southerly declination of +5
on December 3. The comet was last detected on 1991 February 9.98 and February 9.99, when astronomers at Oak Ridge Observatory (Massachusetts, USA) acquired CCD images using the 155-cm reflector. No physical descriptions were provided. The position was α = 2h 13.7m, δ = +10
420 (2000) on the last image. The first parabolic orbit was calculated by D. W. E. Green and was published on 1990 September 20. It was based on 12 positions from 1990 September 15–20. The perihelion date was determined as 527

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1991 February 24.85; however, Green noted it was very uncertain and added, “it is possible that this is a short-period comet.” B. G. Marsden calculated a revised orbit, which was published on October 4. He used 14 positions from September 15–21 and determined the perihelion date as February 23.04. The first elliptical orbit was calculated by Marsden and was published on November 2. He used 30 positions from September 15–30 and included perturbations by all nine planets. The result was a perihelion date of November 8.78 and a period of 6.42 years. As further positions were reported, S. Nakano calculated revised orbits, which were published on 1990 December 2 and 1991 January 30. The first orbit revealed a perihelion date of November 19.87 and a period of 6.56 years, while the second orbit revealed a perihelion date of November 19.90 and a period of 6.56 years. Two orbits were published which included positions spanning the entire period of visibility. Nakano’s orbit was published on 1991 November 21 and used 45 positions, while K. Muraoka’s orbit was published on 1994 April 24 and used 56 positions. The result was a perihelion date of November 19.88–19.89 and a period of 6.56 years. Multiple apparition orbits have been calculated by K. Kinoshita (1999, 2004, 2007, 2012), P. Rocher (1999, 2005, 2013), Nakano (1997, 2001, 2005), and B. G. Marsden (2005). All of these calculations included full planetary perturbations, while only those published from 2012 onward solved for nongravitational effects. Rocher (2012) also included the relativity effect of the Sun. The general result was a perihelion date of November 19.87 and a period of 6.56 years. The nongravitational terms were within the following ranges: A1 = +1.01 to +1.21 and A2 = 0.0560 to 0.0552. The orbit of Rocher (2013) is given below. T ω Ω (2000.0) i q e 1990 Nov. 19.8740 (TT) 171.0177 218.8553 7.0702 2.082990 0.405669

absolute magnitude: H10 = 12 (Meyer) full moon: Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28 sources: J. E. Mueller, J. D. Mendenhall, H. E. Holt, H. R. Holt, C. M. Olmstead, and J. A. Brown, IAUC, No. 5091 (1990 Sep. 17); J. E. Mueller, J. D. Mendenhall, and D. W. E. Green, IAUC, No. 5094 (1990 Sep. 20); T. Seki and B. G. Marsden, MPC, Nos. 16938, 16994 (1990 Oct. 4); J. E. Mueller, H. E. Holt, H. R. Holt, C. M. Olmstead, J. A. Brown, T. Seki, M. Tsumura, and B. G. Marsden, MPC, Nos. 17088, 17175 (1990 Nov. 2); T. Seki, E. F. Helin, B. P. Roman, K. J. Lawrence, and S. Nakano, MPC, Nos. 17279, 17401 (1990 Dec. 2); C. S. Morris, ICQ, 13 (1991 Jan.), p. 60; T. Kojima, T. Hioki, T. Seki, and S. Nakano, MPC, Nos. 17491, 17596 (1991 Jan. 30); [Oak Ridge], MPC, No. 17855 (1991 Mar. 30); A. Hale, ICQ, 13 (1991 Apr.), p. 83; S. Nakano, MPC, No. 19258 (1991 Nov. 21); K. Muraoka, Nakano Note, No. 615 (1994 Apr. 24); S. Nakano, CCO, 12th ed. (1997), pp. 76–7; 528

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K. Kinoshita correspondence with G. W. Kronk (1999, 2004, 2007, 2012); P. Rocher correspondence with G. W. Kronk (1999, 2005, 2013); S. Nakano, Nakano Note, No. 796 (2001 Apr. 28); B. G. Marsden, CCO, 16th ed. (2005), pp. 130–1; S. Nakano, Nakano Note, No. 1146 (2005 Jan. 4); S. Nakano, Nakano Note, No. 2192 (2012 Feb. 5). 127P/1990 R2 Discovered: 1990 September 14.35 (Δ = 1.14 AU, r = 2.05 AU, Elong. = 145
) (Holt–Olmstead) Last seen: 1990 December 19.17 (Δ = 1.53 AU, r = 2.12 AU, Elong. = 113
) Closest to the Earth: 1990 October 12 (1.0479 AU) 1990 XVIII=1990k Calculated path: PSC (Disc) [Did not leave this constellation] This comet was discovered by H. E. Holt and C. M. Olmstead (Palomar Observatory, California, USA) on films exposed using the 46-cm Schmidt telescope. The exposures had been acquired on 1990 September 14.35, September 14.39, September 16.47, September 16.50, September 17.42, and September 17.45, with H. R. Holt and J. A. Brown assisting. All of the images were eight-minute exposures, except for the two acquired on the 17th, which were “special field” exposures and were nine minutes long. The magnitude was given as 17.2 on the first date, at which time the position was α = 1h 41.9m, δ = +7
530 (2000). The magnitude was given as 17.0 on the 16th. Three observatories provided physical descriptions during the remainder of September. Astronomers at Palomar Observatory determined the photographic magnitude as 17.0 on the 18th and 20th. Photographs by T. Seki (Geisei, Kochi, Japan) revealed a magnitude of about 17 on the 20th, 21st, 26th, and 30th. Astronomers at the Lowell Observatory Anderson Mesa Station (Arizona, USA) detected the comet using the 183-cm reflector and a CCD camera. They gave the magnitude as 16.2 on the 22nd and 16.1 on the 25th. The comet reached a maximum elongation of 177
on October 15. That same night, L. V. Zhuravleva and G. R. Kastel’ (Crimean Astrophysical Observatory-Nauchnyj, Ukraine) photographed the comet and estimated the magnitude as 16.5. Seki photographed the comet on October 20 and 23. He estimated the magnitude as 16.5 on both nights. It should be noted that A. Hale (Las Cruces, New Mexico, USA) and C. S. Morris (Lockwood Valley, California, USA) tried to visually observe the comet. Hale used his 41-cm reflector and checked the comet’s predicted position on September 26. Nothing was detected. He suggested the comet was fainter than magnitude 13.0. Morris examined the comet’s predicted position with his 51-cm reflector on October 14, but failed to see the comet. He suggested the comet was fainter than magnitude 14.0. Seki provided physical descriptions on three nights in November and December. He estimated photographic magnitudes of 17.5 on November 11 and 17 on both December 6 and 7. 529

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The comet was last detected during December 19.10–19.17, in the course of the Second Palomar Sky Survey. Although the photographic plate was exposed by J. E. Mueller using the 122-cm Schmidt telescope, the faint, diffuse trail was not found until M. Meyer (2011) located it in the course of research for this volume of Cometography. He estimated the magnitude as 19. The position at the end of the exposure was α = 1h 00.8m, δ = +18
180 (2000). The first orbit was calculated by B. G. Marsden and was published on 1990 September 21. It was based on 13 positions from September 14–21, revealing a perihelion date of 1990 September 28.11 and a period of 6.20 years. As additional positions were reported, orbits were calculated by S. Nakano, which were published in the Minor Planet Circulars on November 2, December 2, and January 30. On the last date, the perihelion date was determined as October 4.52 and the period was 6.16 years. The first orbits to use positions spanning the entire period of visibility were published by Nakano on 1991 November 21 and Marsden (1993). Both astronomers determined the perihelion date as October 4.52 and the period as 6.16 years. Multiple apparition orbits have been calculated by Marsden (1997, 2001), K. Kinoshita (1998, 2003, 2009, 2013), P. Rocher (1996, 2004, 2010), and Nakano (2000, 2006, 2013). All of these calculations included full planetary perturbations, while those published from 2009 onward also solved for nongravitational effects. The result was a perihelion date of October 4.51 and a period of 6.16 years. The nongravitational terms were given as A1 = 0.23 and A2 = 0.0150 by Kinoshita (2009), A1 = +0.33 and A2 = 0.0106 by Rocher (2010), A1 = +0.29 and A2 = 0.0079 by Nakano (2013), and A1 = +0.38 and A2 = 0.0076 by Kinoshita (2013). The orbit of Nakano (2013) is given below. T 1990 Oct. 4.5117 (TT)

ω 2.5930

Ω (2000.0) 15.3222

i 14.8923

q 2.043364

e 0.392226

absolute magnitude: H10 = 13.5 (Meyer) full moon: Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31 sources: H. E. Holt, C. M. Olmstead, H. R. Holt, and J. A. Brown, IAUC, No. 5093 (1990 Sep. 18); H. E. Holt, C. M. Olmstead, H. R. Holt, J. A. Brown, R. E. McCrosky, C.-Y. Shao, B. G. Marsden, G. V. Williams, and T. Seki, IAUC, No. 5097 (1990 Sep. 21); H. E. Holt, C. M. Olmstead, H. R. Holt, J. A. Brown, [Palomar], T. Seki, and B. G. Marsden, MPC, Nos. 16938, 16994 (1990 Oct. 4); T. Seki, [Anderson Mesa], and S. Nakano, MPC, Nos. 17088, 17175 (1990 Nov. 2); T. Seki and S. Nakano, MPC, Nos. 17279, 17401 (1990 Dec. 2); C. S. Morris, ICQ, 13 (1991 Jan.), p. 60; T. Seki and S. Nakano, MPC, Nos. 17491, 17595 (1991 Jan. 30); A. Hale, ICQ, 13 (1991 Apr.), p. 83; L. V. Zhuravleva, G. R. Kastel’, and S. Nakano, MPC, Nos. 19067, 19257 (1991 Nov. 21); B. G. Marsden, CCO, 8th ed. (1993), pp. 36, 69; P. Rocher 530

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correspondence with G. W. Kronk (1996, 2004, 2010); B. G. Marsden, CCO, 12th ed. (1997), pp. 76–7; K. Kinoshita correspondence with G. W. Kronk (1998, 2003, 2009, 2013); S. Nakano, Nakano Note, No. 710 (2000 May 12); B. G. Marsden, CCO, 14th ed. (2001), pp. 96–7; S. Nakano, Nakano Note, No. 1325 (2006 Apr. 12); M. Meyer, MPC, No. 73038 (2011 Jan. 19); S. Nakano, Nakano Note, No. 2505 (2013 Jun. 12); J. E. Mueller correspondence with G. W. Kronk (2014). 158P/Kowal– Precovered: 1990 September 23.42 (Δ = 3.98 AU, r = 4.68 AU, Elong. = 129
) LINEAR Last seen: 1993 November 9.39 (Δ = 3.84 AU, r = 4.70 AU, Elong. = 147
) Closest to the Earth: 1991 September 16 (3.6338 AU) Calculated path: CAP (Disc), AQR (1991 Jan. 26), PSC (Jun. 13), CET (Aug. 27), AQR (Sep. 2), CET (1992 Jan. 20), PSC (Jan. 21), CET (Feb. 26), PSC (Apr. 26), CET (Jun. 14), PSC (Dec. 9), CET (1993 Jan. 14), ARI (Apr. 10), TAU (May 1), ORI (Jul. 23) The Lincoln Near Earth Asteroid Research (LINEAR) survey found an asteroidal object on 2001 September 12, which was subsequently designated 2001 RG100. It was occasionally observed during the next two years; however, A. E. Gleason (Steward Observatory, Kitt Peak, Arizona, USA) acquired images with the 91-cm reflector on 2003 November 26, which revealed that this object was actually a comet, as it was exhibiting a coma and tail. This inspired R. Stoss (Darmstadt, Germany) to began searching through Digital Sky Survey images where he discovered that this comet had been photographed in 1990 and 1993. The 1990 image was a scan of a 65-minute exposure on a Kodak IIIa-F (red) photographic plate obtained at Siding Spring Observatory (New South Wales, Australia) using the 122-cm Schmidt telescope. The comet had moved very little during the exposure, so that Stoss could only measure a single position. It was α = 20h 47.5m, δ = 18
090 (2000) on September 23.42. The 1993 image was a scan of a 40-minute exposure on a Kodak IIIa-J (blue) photographic plate obtained at Palomar Observatory (California, USA) using the 122-cm Schmidt telescope. Stoss was able to measure positions for each end of the diffuse trail. The position at the end of the exposure on November 9.39 was α = 5h 16.6m, δ = +14
180 (2000). Stoss’ positions were announced on Minor Planet Electronic Circular 2003W74, which was published on 2003 November 29. This included orbits for the 1992 and 2002 apparitions of this comet. S. Nakano published Nakano Note number 995 on 2003 December 3. He integrated the comet’s motion backwards and found it was identical to a comet announced on International Astronomical Union Circular number 3395, which was published on 1979 August 27. This publication noted that C. T. Kowal (Palomar Observatory) had found a comet on photographs exposed on 1979 July 24, 25, and 27. Although B. G. Marsden had published a parabolic orbit for Kowal’s comet, no additional observations were made and it had been considered lost. 531

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M. Meyer and G. W. Kronk examined the digital images from 1990 and 1993. Meyer determined the comet’s magnitude as 19.8 on 1990 September 23 and 18.9 on 1993 November 9. Kronk noted that the comet exhibited a coma on both images, while the 1993 image also revealed a faint tail extending westward. During the period between these two images, the comet reached minimum elongations of 2
on 1991 February 22, 5
on 1992 April 3, and 6
on 1993 May 16. It had reached maximum elongations of 174
on 1991 September 17 and 170
on 1992 October 28. The comet attained its most southerly declination of 18.5
on 1990 October 17 and attained its most northerly declination of +16
on 1993 August 15. Multiple apparition orbits have been calculated by Nakano (2003, 2007, 2009), K. Kinoshita (2003, 2009), and P. Rocher (2006, 2012, 2015). All of these calculations included full planetary perturbations. The result was a perihelion date of 1992 February 29.98–March 1.03 and a period of 10.39 years. The orbit of Rocher (2015) is given below. T ω Ω (2000.0) i q e 1992 Feb. 29.9971 (TT) 233.8598 137.3634 7.8905 4.629127 0.028089

absolute magnitude: H10 = 9.5 (Meyer) full moon: Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30, Apr. 28, May 28, Jun. 27, Jul. 26, Aug. 25, Sep. 23, Oct. 23, Nov. 21, Dec. 21, 1992 Jan. 19, Feb. 18, Mar. 18, Apr. 17, May 16, Jun. 15, Jul. 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6, Mar. 8, Apr. 6, May 6, Jun. 4, Jul. 3, Aug. 2, Sep. 1, Sep. 30, Oct. 30, Nov. 29 sources: C. T. Kowal, IAUC, No. 3395 (1979 Aug. 27); C. T. Kowal and B. G. Marsden, IAUC, No. 3397 (1979 Aug. 29); B. G. Marsden, IAUC, No. 3404 (1979 Sep. 14); C. T. Kowal, MPC, No. 4998 (1979 Nov. 1); K. Kinoshita correspondence with G. W. Kronk (2003, 2009); A. E. Gleason, IAUC, No. 8244 (2003 Nov. 28); R. Stoss, MPEC, No. 2003-W74 (2003 Nov. 29); S. Nakano, Nakano Note, No. 995 (2003 Dec. 3); R. Stoss, MPC, No. 50353 (2003 Dec. 8); P. Rocher correspondence with G. W. Kronk (2006, 2012, 2015); S. Nakano, Nakano Note, No. 1447 (2007 Mar. 4); S. Nakano, Nakano Note, No. 1776 (2009 Apr. 23). 136P/1990 S1 Prediscovery: 1990 September 17.42 (Δ = 2.10 AU, r = 3.01 AU, Elong. = 149
) (Mueller 3) Discovered: 1990 September 24.36 (Δ = 2.07 AU, r = 3.01 AU, Elong. = 156
) Last seen: 1990 December 15.06 (Δ = 2.58 AU, r = 3.08 AU, Elong. = 112
) 1990 XIII=1990l Closest to the Earth: 1990 October 8 (2.0377 AU) Calculated path: CET (Pre) [Did not leave this constellation] In the course of the Second Palomar Sky Survey, J. E. Mueller (Palomar Observatory, California, USA) was examining a pair of plates obtained with the 122-cm Schmidt telescope by C. Brewer and J. D. Mendenhall when she 532

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noticed a diffuse trail. The plates were exposed on 1990 September 24.36 and September 25.35. She estimated the magnitude as 18 and reported a faint tail toward the west. The position on the first date was given as α = 1h 38.8m, δ = 2
130 (2000). E. L. G. Bowell (Lowell Observatory, Arizona, USA) reported prediscovery images a few days later after examining film exposed with the 46-cm Schmidt telescope at Palomar Observatory. The plates had been exposed by H. E. Holt, H. R. Holt, C. M. Olmstead, and J. A. Brown on September 17.42 and September 19.45. The magnitude was given as 17.5. The first observations following the discovery announcement came from T. Seki (Geisei, Kochi, Japan). He photographed the comet on September 30 with his 60-cm reflector and estimated the magnitude as 18. Seki obtained additional photographs on October 19 and 20, estimating the magnitude as 19 and 18.5, respectively. Although observations were also obtained at Oak Ridge Observatory (Massachusetts, USA) and Siding Spring Observatory (New South Wales, Australia), it was Seki who continued to provide the only magnitude estimates, giving values of 18 on November 21, 18.5 on November 23, and 18.5 on December 7. The comet reached a maximum elongation of 168
on October 12 and attained its most southerly declination of 5
on November 14. The comet was last detected during December 15.03–15.06, when astronomers at Oak Ridge Observatory obtained CCD images of the comet using the 155-cm reflector. The position on the last image was given as α = 1h 11.9m, δ = 4
080 (2000). The first orbit was calculated by E. L. G. Bowell and was published on 1990 September 28. Bowell used eight positions from 1990 September 17–25, as well as full planetary perturbations. The orbit was elliptical with a perihelion date of 1990 July 26.02 and a period of 8.56 years. As positions continued to be reported, S. Nakano calculated revised elliptical orbits that were published on November 2, December 2, and January 30. The last orbit was based on 17 positions from September 17 to December 7 and included full planetary perturbations. The perihelion date was determined as August 1.77 and the period was 8.65 years. Two orbits were calculated which used positions spanning the entire period of visibility. The Minor Planet Circulars published an orbit by Nakano on 1991 November 21, which used 19 positions to determine the perihelion date as August 1.93 and the period as 8.65 years. P. Rocher (1995) used 21 positions to determine the perihelion date as August 1.99 and the period as 8.65 years. Multiple apparition orbits have been calculated by B. G. Marsden (1999, 2005), K. Kinoshita (1999, 2001, 2009), Rocher (2000, 2002, 2006, 2009), Nakano (2004, 2013), and T. Kobayashi (2013). All of these calculations included full planetary perturbations, while only those published from 2009 onward solved for nongravitational effects. The result was a perihelion date of August 1.70–1.76 and a period of 8.64–8.65 years. Standard 533

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nongravitational terms were determined as A1 = 8.89 and A2 = 1.7233 by Kinoshita (2009) and A1 = 21.35 and A2 = 0.9113 by Kobayashi. Nakano (2013) solved for nongravitational effects based on S. Yabushita’s theory of sublimating carbon monoxide (or molecular nitrogen). He determined the terms as Y1 = 0.76 and Y2 = 0.0003. The orbit of Kobayashi (2013) is given below. T ω Ω (2000.0) i q e 1990 Aug. 1.7285 (TT) 225.9855 138.0123 9.4312 2.997895 0.288275

absolute magnitude: H10 = 11.5 (Meyer) full moon: Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31 sources: J. E. Mueller, C. Brewer, and J. D. Mendenhall, IAUC, No. 5102 (1990 Sep. 26); E. L. G. Bowell, H. E. Holt, H. R. Holt, C. M. Olmstead, and J. A. Brown, IAUC, No. 5105 (1990 Sep. 28); J. E. Mueller, J. D. Mendenhall, H. E. Holt, H. R. Holt, C. M. Olmstead, J. A. Brown, T. Seki, and S. Nakano, MPC, Nos. 17088, 17174 (1990 Nov. 2); T. Seki, [Oak Ridge], [Siding Spring], and S. Nakano, MPC, Nos. 17279, 17400 (1990 Dec. 2); [Oak Ridge], T. Seki, and S. Nakano, MPC, Nos. 17491, 17595 (1991 Jan. 30); [Oak Ridge], MPC, No. 17685 (1991 Feb. 28); S. Nakano, MPC, No. 19257 (1991 Nov. 21); P. Rocher correspondence with G. W. Kronk (1995, 2000, 2002, 2006, 2009); B. G. Marsden, CCO, 13th ed. (1999), pp. 82–3; K. Kinoshita correspondence with G. W. Kronk (1999, 2001, 2009); S. Nakano, Nakano Note, No. 1057 (2004 Apr. 8); B. G. Marsden, CCO, 16th ed. (2005), pp. 130–1; S. Nakano and T. Kobayashi, Nakano Note, No. 2510 (2013 Jun. 12). 163P/NEAT Precovered: 1990 October 24.43 (Δ = 1.26 AU, r = 2.06 AU, Elong. = 131
) Last seen: 1991 February 9.17 (Δ = 1.31 AU, r = 1.95 AU, Elong. = 116
) Closest to the Earth: 1990 December 13 (0.9866 AU) Calculated path: ORI (Disc), TAU (1991 Jan. 5) The Near-Earth Asteroid Tracking (NEAT) survey discovered this comet on 2004 November 5, using the 122-cm Schmidt telescope at Palomar Observatory (California, USA). The discovery details and an initial parabolic orbit were published on November 6. This orbit helped in the discovery of images that had been obtained by the Lowell Observatory Near-Earth Object Search (LONEOS) survey on October 9, which in turn led to the calculation of an elliptical orbit with a period of about seven years. As November progressed, M. Meyer began checking for precovery images of this comet. He requested several observers to send their precise positions to him, so that he could calculate a better orbit. As the orbit improved, he found the comet on two images acquired by NEAT in 1997. Calculating still another orbit, he then began checking the Digital Sky Survey and very quickly found the comet on three images obtained during 534

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1990–1991 with the 122-cm Schmidt telescope and Kodak IIIa-F (red) photographic plates in the course of the Second Palomar Sky Survey. The first sky survey image was a 70-minute exposure obtained during 1990 October 24.42–24.47. The nuclear magnitude was determined as 19.7–19.8, while the position at the beginning of the exposure was α = 5h 14.5m, δ = +8
020 (2000). The second exposure was 73 minutes in duration on October 26 and revealed the nuclear magnitude as 19.0. The final image was a 65-minute exposure during 1991 February 9.13–9.17. The nuclear magnitude was given as 20.6 at the beginning of the trail and 19.7 at the end of the trail. The comet’s position at the end of the exposure was α = 4h 58.0m, δ = +22
180 (2000). Meyer noted that this last image showed a faint tail. The comet reached a maximum elongation of 168
on December 9. Multiple apparition orbits have been calculated by B. G. Marsden (2004, 2005), S. Nakano (2004, 2005, 2011), P. Rocher (2005, 2012), and K. Kinoshita (2009, 2011). All of these calculations included full planetary perturbations. The result was a perihelion date of 1991 January 13.35–13.36 and a period of 7.06 years. The orbit of Nakano (2011) is given below. T ω Ω (2000.0) i q e 1991 Jan. 13.3554 (TT) 347.0364 103.8835 12.4403 1.940884 0.472385

absolute magnitude: H10 = 16 (Meyer) full moon: Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28 sources: M. Meyer and B. G. Marsden, MPEC, No. 2004-X29 (2004 Dec. 8); M. Meyer, MPC, No. 53303 (2004 Dec. 26); S. Nakano, Nakano Note, No. 1130 (2004 Dec. 26); B. G. Marsden, CCO, 16th ed. (2005), pp. 134–5; P. Rocher correspondence with G. W. Kronk (2005, 2012); S. Nakano, Nakano Note, No. 1284 (2005 Oct. 30); K. Kinoshita correspondence with G. W. Kronk (2009, 2011); S. Nakano, Nakano Note, No. 2129 (2011 Oct. 12). 52P/Harrington– Precovered: 1990 September 18.28 (Δ = 2.11 AU, r = 3.02 AU, Elong. = 149
) Abell Recovered: 1990 October 22.26 (Δ = 1.86 AU, r = 2.83 AU, Elong. = 165
) Last seen: 1990 October 23.94 (Δ = 1.85 AU, r = 2.82 AU, Elong. = 163
) 1991 X=1990m Closest to the Earth: 1990 November 1 (1.8436 AU) Calculated path: PSC (Rec) [Did not leave this constellation] Two predictions were published for this apparition, both of which used positions from 1968–1984 and full planetary perturbations. S. Nakano (1987) used 23 positions and predicted that the comet would next arrive at perihelion on 1991 July 6.93. G. Forti (1989) used 30 positions and solved for nongravitational effects. He predicted the next perihelion would occur on July 6.94. This comet was recovered during 1990 October 22.26–22.28, when J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) located it on three 535

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CCD images acquired with the 91-cm reflector. He gave the nuclear magnitude as 21.0. The position on the first image was α = 0h 49.8m, δ = +17
160 (2000). The comet had reached a maximum elongation of 169
on October 13. The comet was confirmed at two locations on October 23, which was also the final day of observations. Scotti acquired three images during October 23.18–23.20 and gave the nuclear magnitude as 20.8. H. Rickman and G. Tancredi (Pic du Midi Observatory, France) acquired CCD images on October 23.89 and October 23.94, using the 201-cm reflector and an R filter. They said the comet appeared stellar and gave the R magnitude as 20.3. The position on the last image was α = 0h 48.2m, δ = +17
100 (2000). J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton (2000) analyzed the Pic du Midi images as part of a program to study cometary nuclei. They determined the radius of the nucleus as 1.4 kilometers. Precovery images of the comet were found by J. B. Gibson (Palomar Observatory, California, USA). He had used the 152-cm reflector to acquire CCD images on 1990 September 18.28 and September 18.30. He estimated the nuclear magnitude as 22 and indicated a position of α = 1h 18.9m, δ = +18
060 (2000). Multiple apparition orbits have been calculated by Nakano (1996, 1999, 2003, 2011, 2013), K. Kinoshita (1999, 2001, 2007, 2013), and P. Rocher (2000, 2005). All of these calculations included full planetary perturbations, while those published from 1999 onward also solved for nongravitational effects. The result was a perihelion date of July 6.93 and a period of 7.59 years. The nongravitational terms were within the following ranges: A1 = +0.10 to +0.40 and A2 = +0.0033 to +0.0072. The orbit of Nakano (2013) is given below. T ω Ω (2000.0) i q e 1991 Jul. 6.9296 (TT) 138.6648 337.3441 10.1826 1.774389 0.540437

absolute magnitude: H10 = 15 (Meyer) full moon: Sep. 5, Oct. 4, Nov. 2 sources: S. Nakano, Nakano Note, No. 516 (1987 Aug. 20); G. Forti, AAP, 215 (1989), pp. 382, 384; J. V. Scotti, H. Rickman, and G. Tancredi, IAUC, No. 5129 (1990 October 31); J. V. Scotti, H. Rickman, and G. Tancredi, MPC, No. 17279 (1990 Dec. 2); J. B. Gibson, MPC, No. 17685 (1991 Feb. 28); S. Nakano, Nakano Note, No. 630 (1996 Apr. 11); S. Nakano, CCO, 13th ed. (1999), pp. 68–9; K. Kinoshita correspondence with G. W. Kronk (1999, 2001, 2007, 2013); P. Rocher correspondence with G. W. Kronk (2000, 2005, 2014); J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton, Icarus, 147 (2000 Sep.), pp. 164–5, 174; S. Nakano, Nakano Note, No. 938 (2003 Apr. 20); S. Nakano, Nakano Note, No. 2137 (2011 Oct. 30); S. Nakano, Nakano Note, No. 2590 (2013 Dec. 19).

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69P/Taylor Recovered: 1990 November 11.51 (Δ = 1.34 AU, r = 1.99 AU, Elong. = 116
) Last seen: 1991 March 21.02 (Δ = 1.51 AU, r = 2.07 AU, Elong. = 109
) 1990 XXX=1990n Closest to the Earth: 1991 January 8 (0.9693 AU) Calculated path: CMi (Rec), GEM (Dec. 9), AUR (1991 Mar. 10), LYN (Mar. 15) A prediction for the return of this comet was published by B. G. Marsden (1987, 1989). He used 42 positions from 1976–1984 and included full planetary perturbations. He then integrated the comet’s motion to this apparition and predicted the perihelion date as 1990 December 28.93. This comet was recovered by J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) on three CCD images acquired with the 91-cm reflector during 1990 November 11.51–11.53. He gave the magnitude as 19.7, noting a diffuse coma 800 across and “indications” of a tail extending 900 in about PA 350
. The position on the first image was α = 7h 26.9m, δ = +9
080 (2000). Scotti found the comet on five additional images acquired using the same telescope during November 12.49–12.54. An independent recovery came from T. Seki (Geisei, Kochi, Japan), who photographed the comet using his 60-cm reflector on November 11.76. He estimated the magnitude as 19.5. Only two observatories followed the comet during the remainder of 1990. Using the 155-cm reflector and a CCD camera, astronomers at Oak Ridge Observatory (Massachusetts, USA), acquired images on November 15, November 21, December 13, and December 17. No physical descriptions were provided. Seki photographed the comet on December 19 and 24, estimating the magnitude as 18.5 and 18, respectively. The comet reached a maximum elongation of 179
on 1991 January 10. It was also most observed in January, although physical descriptions were only provided for four nights. Seki estimated the magnitude as 16.5 on the 6th. At Chiyoda Observatory, T. Kojima (Gunma, Japan) photographed the comet using his 25-cm reflector on the 8th and 22nd, estimating the magnitude as 15.5 and 15, respectively. Astronomers at Oak Ridge Observatory described the comet as stellar on January 16. Only a few observations were made in February, with the only physical description coming on the 12th, when Kojima estimated the magnitude as 16. Astronomers at Oak Ridge Observatory provided the only observations in March, which was also the final month of observations. Using the 155-cm reflector, they obtained CCD images during March 13.08–13.11, March 17.03–17.05, and March 21.01–21.02. The comet was described as weak and diffuse on the last night, while the position on the last image was α = 7h 36.7m, δ = +35
450 (2000). Visual observations were attempted on several occasions by A. Hale (Las Cruces, New Mexico, USA), using his 41-cm reflector. He was unsuccessful on five nights during the period spanning 1990 December 10 to 1991 February 6 and concluded the comet was probably fainter than magnitude 13.5.

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Another unsuccessful attempt on 1991 June 15 brought him to surmise that the comet was fainter than magnitude 13.0. Multiple apparition orbits have been calculated by Marsden (1994, 2001), P. Rocher (1998, 1999), S. Nakano (1999, 2001), and K. Kinoshita (2000, 2006). All of these calculations included full planetary perturbations, while nongravitational effects were solved by everyone, except Marsden (1994), Nakano (1999), and Marsden (2001). The result was a perihelion date of December 28.85–28.86 and a period of 6.97 years. Rocher (1998) used positions from 1984–1998 to determined nongravitational terms of A1 = +3.03 and A2 = 0.0517. Rocher (1999), Kinoshita (2000) and Nakano (2001) used positions from only the 1990 and 1997 apparitions and gave terms within the following ranges: A1 = 0.43 to +4.27 and A2 = +0.4350 to +1.0120. Kinoshita (2006) used positions from 1991–2005 and determined nongravitational terms of A1 = +0.05 and A2 = +0.0302. The orbit of Marsden (2001) is given below. T ω Ω (2000.0) i q e 1990 Dec. 28.8529 (TT) 355.5534 108.8703 20.5515 1.950204 0.465607

absolute magnitude: pre-perihelion: H10 = 15.5, post-perihelion: H10 = 12.5 (Meyer) full moon: Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30 sources: B. G. Marsden, MPC, No. 12136 (1987 Aug. 9); B. G. Marsden, BAA Handbook for 1990 (1989), p. 73; J. V. Scotti, IAUC, No. 5134 (1990 Nov. 13); J. V. Scotti, T. Seki, and [Oak Ridge], MPC, No. 17279 (1990 Dec. 2); [Oak Ridge] and T. Seki, MPC, No. 17491 (1991 Jan. 30); [Oak Ridge], MPC, Nos. 17685, 17688 (1991 Feb. 28); [Oak Ridge], MPC, Nos. 18012, 18015 (1991 Apr. 28); T. Kojima, MPC, No. 18493 (1991 Aug. 25); T. Kojima, MPC, No. 19068 (1991 Nov. 21); B. G. Marsden, CCO, 9th ed. (1994), pp. 36, 70; [Palomar], MPC, No. 28917 (1997 Feb. 22); P. Rocher correspondence with G. W. Kronk (1998, 1999); S. Nakano, CCO, 13th ed. (1999), pp. 72–3; K. Kinoshita correspondence with G. W. Kronk (2000, 2006); B. G. Marsden, CCO, 14th ed. (2001), pp. 86–7. 192P/1990 V1 Prediscovery: 1990 October 24.60 (Δ = 0.63 AU, r = 1.59 AU, Elong. = 154
) (Shoemaker– Discovered: 1990 November 15.32 (Δ = 0.74 AU, r = 1.68 AU, Elong. = 151
) Levy 1) Last seen: 1991 January 18.06 (Δ = 1.63 AU, r = 2.09 AU, Elong. = 104
) Closest to the Earth: 1990 October 15 (0.6222 AU) 1990 XV=1990o Calculated path: CET (Pre), PSC (Nov. 20), ARI (Dec. 5) In the course of the Palomar Asteroid and Comet Survey, C. S. Shoemaker, E. M. Shoemaker, and D. H. Levy (Palomar Observatory, California, USA) discovered this comet on film exposed with the 46-cm Schmidt telescope on 1990 November 15.32, November 16.27, and November 16.30. They estimated the magnitude as 13 on the first date, at which time the position was 538

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α = 1h 51.4m, δ = 0
100 (2000). The comet exhibited a strong central condensation. Several independent confirmations came on November 17. C.-Y. Shao (Oak Ridge Observatory, Massachusetts, USA) obtained three CCD images using the 155-cm reflector. Astronomers at Palomar obtained a single image. A. Sugie (Dynic Astronomical Observatory, Shiga, Japan) obtained two images using the 25-cm Schmidt telescope and estimated the magnitude as 14. Visual observations were also made by A. Hale (Las Cruces, New Mexico, USA) and Levy (Tucson, Arizona, USA). Both observers used 41-cm reflectors, with Hale giving the magnitude as 12.6 and Levy giving it as 12.8. Hale noted the comet was diffuse and moderately condensed. Two prediscovery images were announced by T. Kojima (Chiyoda, Gunma, Japan), both having been obtained by Kojima and T. Ohtsuka while using a 25-cm reflector. The first position was announced on December 2 and had been acquired on November 10.56. The magnitude was estimated as 13.5. The second position was announced on 1991 January 30 and had been obtained on October 24.60. The magnitude was estimated as 14. The position on the October image was α = 2h 12.8m, δ = 14
110 (2000). The comet had reached a maximum elongation of 156
on November 2. Several visual observations were made during the remainder of November. Hale, G. Comello (Netherlands), and R. J. Bouma (Netherlands) saw the comet on the 19th. Hale determined the magnitude as 12.6. Comello was using a 28-cm reflector and estimated the magnitude as 12.8. He also reported a very slightly condensed coma about 1.50 across. Bouma saw the comet with his 25-cm reflector a little over four hours after Comello made his observation and also estimated the magnitude as 12.8. He noted a slightly condensed coma. On the 21st, the comet was observed by A. R. Pearce (Scarborough, Western Australia, Australia), Bouma, and Comello. Pearce was using his 41-cm reflector and judged the magnitude as 12.8. Bouma gave the magnitude as 12.9. He added that the coma was very slightly condensed and 10 across. Comello said the magnitude was 12.7, while the coma was very slightly condensed and about 10 across. Observations by C. S. Morris (Pine Mountain Club, California, USA) and Pearce on the 22nd revealed a magnitude of 12.8. Morris added that the coma was uncondensed and 2.20 across. Morris said the comet still appeared uncondensed on the 24th and 25th, giving the magnitude as 13.3 and 13.5, respectively. He added that the coma was 2.00 across on the first night and 1.20 across on the second night. The comet was only followed during the first half of December. T. Seki (Geisei, Kochi, Japan) photographed it using his 60-cm reflector on the 6th, estimating the magnitude as 14.5. Hale observed the comet on the 7th, describing it as “faint, vague and diffuse,” with a magnitude of 13.2. Morris looked for the comet on the 9th, using his 26-cm reflector. He wrote, “comet not definitely seen; suspect of [magnitude] 13.6–13.8 was in comet’s 539

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position.” Astronomers at Oak Ridge Observatory detected the comet on CCD images obtained on the 14th and 15th, but no descriptive information was provided. Hale examined the comet’s predicted position on December 19 with his 41-cm reflector, but no trace was found. He suggested the comet was then fainter than magnitude 13.5. The next observation was obtained on 1991 January 5, when E. Meyer, E. Obermair, and H. Raab (Davidschlag, Austria) obtained two photographs at a private observatory equipped with a 29-cm reflector. They estimated the comet’s magnitude as 15. The comet was last detected on January 18.05 and January 18.06, when astronomers at Oak Ridge Observatory (Massachusetts, USA) obtained CCD images using the 155-cm reflector. The position on the last date was α = 2h 22.5m, δ = +24
160 (2000). The first parabolic orbit was calculated by S. Nakano and was published on 1990 November 19. He used nine positions from November 15–18 and determined the perihelion date as 1990 September 17.38. The first elliptical orbit was published by B. G. Marsden on December 2. He used 25 positions from November 10–23 and included perturbations by all nine planets. The result was a perihelion date of September 18.57 and a period of 17.80 years. Marsden published a revised orbit on 1991 January 30. This used 34 positions from 1990 October 24 to 1991 January 5 and included perturbations by all nine planets. The result was a perihelion date of September 18.58 and a period of 17.27 years. Several orbits were calculated that used positions spanning the entire period of visibility. Nakano (1991, 2004), P. Rocher (1995), K. Kinoshita (1998), and Marsden (2005) determined very similar orbits, with a perihelion date of September 18.59 and a period of 17.26 years. Multiple apparition orbits have been calculated by Kinoshita (2007), Nakano (2007), and Rocher (2008). All of these calculations included full planetary perturbations, while Rocher also included the relativity effect of the Sun. The result was a perihelion date of September 18.59 and a period of 17.28 years. Rocher’s orbit is given below. T ω Ω (2000.0) i q e 1990 Sep. 18.5919 (TT) 310.6224 52.0444 24.3334 1.524077 0.771955

absolute magnitude: H10 = 11, from visual observations (Meyer) full moon: Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30 sources: C. S. Shoemaker, E. M. Shoemaker, and D. H. Levy, IAUC, No. 5135 (1990 Nov. 16); C.-Y. Shao, [Palomar], A. Sugie, S. Nakano, A. Hale, and D. H. Levy, IAUC, No. 5136 (1990 Nov. 19); T. Kojima, T. Ohtsuka, C. S. Shoemaker, E. M. Shoemaker, D. H. Levy, C.-Y. Shao, [Palomar], A. Sugie, T. Kojima, T. Ohtsuka, and B. G. Marsden, MPC, Nos. 17279–80, 17400 (1990 Dec. 2); B. G. Marsden, A. R. Pearce, C. S. Morris, and A. Hale, IAUC, No. 5143 (1990 Dec. 10); A. R. Pearce and C. S. Morris, ICQ, 540

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13 (1991 Jan.), pp. 8, 64; T. Kojima, T. Ohtsuka, E. Meyer, E. Obermair, H. Raab, T. Seki, [Oak Ridge], and B. G. Marsden, MPC, Nos. 17491, 17595 (1991 Jan. 30); [Oak Ridge], MPC, No. 17685 (1991 Feb. 28); A. Hale, ICQ, 13 (1991 Apr.), pp. 72, 85; G. Comello, ICQ, 13 (1991 Jul.), p. 140; S. Nakano, MPC, No. 19257 (1991 Nov. 21); R. J. Bouma, ICQ, 16 (1994 Apr.), p. 76; P. Rocher correspondence with G. W. Kronk (1995, 2008); K. Kinoshita correspondence with G. W. Kronk (1998, 2007); S. Nakano, Nakano Note, No. 1060 (2004 Apr. 8); B. G. Marsden, CCO, 16th ed. (2005), pp. 36–7; S. Nakano, Nakano Note, No. 1539 (2007 Oct. 18). 137P/1990 UL3 Prediscovery: 1990 September 16.39 (Δ = 0.95 AU, r = 1.85 AU, Elong. = 142
) (Shoemaker– Discovered: 1990 October 25.37 (Δ = 0.87 AU, r = 1.87 AU, Elong. = 175
) Levy 2) Last seen: 1992 February 5.16 (Δ = 3.26 AU, r = 4.24 AU, Elong. = 173
) Closest to the Earth: 1990 October 15 (0.8642 AU) 1990 XVI=1990p Calculated path: ARI (Pre), PSC (Oct. 16), ARI (Dec. 1), TAU (1991 Feb. 19), ORI (May 12), GEM (May 29), CNC (Jul. 28), LEO (Oct. 11), CNC (1992 Feb. 2) In the course of the Palomar Asteroid and Comet Survey (PACS), C. S. Shoemaker, E. M. Shoemaker, and D. H. Levy (Palomar Observatory, California, USA) discovered an asteroidal object on film exposed with the 46-cm Schmidt telescope during 1990 October 25.37–25.41, November 13.24–13.28, and November 15.24–15.27. They estimated the magnitude as 17 on the first date and 17.7 on the second. The position on the first date was α = 1h 44.6m, δ = +15
200 (2000). Prediscovery images were found on several photographs obtained by various surveys at Palomar Observatory, with the object always appearing asteroidal. Film was exposed for PACS by H. E. Holt, H. R. Holt, C. M. Olmstead, and J. A. Brown on September 17.44–17.47 and September 20.51. The object’s magnitude was determined as 17.6 on the first date. Shortly thereafter, the object was also found on film exposed on October 14.40 and October 16.36 for the Palomar Planet-Crossing Asteroid Survey by E. F. Helin, B. P. Roman, and K. J. Lawrence. The magnitude was given as 15.7 on the first date. While doing research for this volume, M. Meyer found a prediscovery image on a photographic plate exposed during September 16.39–16.45 for the Second Palomar Sky Survey. He gave the nuclear magnitude as 16.9–17.3. The position on the first image was α = 1h 47.4m, δ = +17
500 (2000). The comet had reached a maximum elongation of 176
on October 23. International Astronomical Union Circular number 5149 announced that this asteroidal object was actually a comet. S. M. Larson and D. H. Levy (Catalina Station, Mt. Bigelow, Arizona, USA) obtained seven CCD images on December 19, using the 154-cm reflector and a Cousins red-band filter. Co-adding the images revealed a tail extending 2800 in PA 58
. Twenty-four hours later, Larson and Levy detected the tail on seven Cousin red-band images and five Harris visual-band images, but it was not visible on Harris 541

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blue-band images acquired in poor seeing. B. A. Skiff (Lowell Observatory Anderson Mesa Station, Arizona, USA) confirmed the tail. He said a threeminute exposure on December 7, using the 107-cm Ritchey-Chretien telescope and a CCD camera, revealed a straight, diffuse tail extending 2900 in PA 67
. Skiff determined the nuclear magnitude as 17.0. Two other observatories provided descriptions of the comet in December. At Geisei (Kochi, Japan), T. Seki obtained a photograph on December 7 that revealed a nuclear magnitude of 16.5. Astronomers at Mauna Kea (Hawaii, USA) obtained images on December 11 and 12, giving nuclear magnitudes of 17.7 and 17.6, respectively. After having moved southward since its discovery, the comet attained a declination of +12
on December 10 and then began a northward motion. The last astrometric position was acquired on 1991 January 15.12, when Skiff and his colleague, K. L. Faul, (Lowell Observatory Anderson Mesa Station) obtained two CCD images using the 107-cm Ritchey-Chretien telescope. The nuclear magnitude was determined as 18.2, and they noted a straight, narrow tail extending 5900 in PA 70
. The position on the last image was α = 2h 30.3m, δ = +13
410 (2000). The comet attained its most northerly declination of +21
on May 13 and then attained its most southerly declination of +8
on December 21. It reached a minimum elongation of 3
on July 15. The comet was last detected during 1992 February 3.20–3.22 and February 5.14–5.16, by astronomers at La Silla Observatory (Chile) using the 154-cm reflector. J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton (2000) analyzed these images as part of a program to study cometary nuclei. They said the comet had a “star-like appearance,” determining the V magnitude as 20.1–20.2 on the 3rd and 20.4–20.5 on the 5th. They determined the radius of the nucleus as 4.2 kilometers and added that the comet was “dynamically old.” The predicted position at the time of the last observation was α = 9h 19.5m, δ = +9
200 (2000). The first orbit was calculated by G. V. Williams and was published on 1990 November 29. Williams used nine positions from 1990 September 17 to November 15 and perturbations by all nine planets. The result was a perihelion date of 1990 September 25.40 and a period of 9.27 years. This orbit proved to be an excellent representation of the comet’s motion, as shown by an orbit published by B. G. Marsden on 1991 January 30. Marsden used 19 positions from September 17 to December 18 and included perturbations by all nine planets. The result was a perihelion date of September 25.39 and a period of 9.28 years. The first orbit that used positions spanning the entire period of visibility was calculated by S. Nakano (1991). He took 20 positions and included full planetary perturbations. He determined the perihelion date as September 25.39 and the period as 9.28 years. Multiple apparition orbits have been calculated by Williams (1999), Nakano (1999, 2006, 2015), K. Kinoshita (2001, 2009, 2013), and P. Rocher 542

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(2000, 2001, 2014). All of these calculations included full planetary perturbations. The result was a perihelion date of September 25.37 and a period of 9.27 years. The orbit of Nakano (2015) is given below. T ω Ω (2000.0) i q e 1990 Sep. 25.3745 (TT) 140.0695 235.9949 4.6374 1.843957 0.582271

absolute magnitude: H10 = 14 (Meyer) full moon: Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30 sources: C. S. Shoemaker, E. M. Shoemaker, D. H. Levy, H. E. Holt, H. R. Holt, C. M. Olmstead, J. A. Brown, and G. V. Williams, IAUC, No. 5138 (1990 Nov. 29); S, M. Larson, D. H. Levy, and B. A. Skiff, IAUC, No. 5149 (1990 Dec. 21); B. A. Skiff, T. Seki, [Mauna Kea], and B. G. Marsden, MPC, Nos. 17491–3, 17595 (1991 Jan. 30); S. Nakano, Nakano Note, No. 547 (1991 Feb. 2); B. A. Skiff and K. L. Faul, MPC, Nos. 17685, 17688 (1991 Feb. 28); P. Rocher correspondence with G. W. Kronk (2000, 2001, 2014); G. V. Williams, CCO, 13th ed. (1999), pp. 82–3; S. Nakano, Nakano Note, No. 721 (1999 Nov. 4); J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton, Icarus, 147 (2000 Sep.), pp. 164–5, 174; K. Kinoshita correspondence with G. W. Kronk (2001, 2009, 2013); S. Nakano, Nakano Note, No. 1314 (2006 Apr. 8); J. E. Mueller correspondence with G. W. Kronk (2010); S. Nakano, Nakano Note, No. 2886 (2015 May 8). 96P/Machholz 1 Recovered: Visible throughout orbit Last seen: Visible throughout orbit 1991 XII Closest to the Earth: 1991 June 29 (0.8968 AU) Calculated path: SGR (Aphelion), CrA (1989 Jun. 24), SGR (1990 Jan. 11), TEL (Jun. 6), CrA (Oct. 18), SGR (Dec. 22), MIC (1991 Feb. 7), GRU (Mar. 12), SCL (May 1), FOR (Jun. 2), ERI (Jun. 20), LEP (Jun. 28), ORI (Jul. 3), MON (Jul. 7), ORI (Jul. 8), MON (Jul. 10), GEM (Jul. 16), CNC (Jul. 22), LEO (Jul. 27), LMi (Jul. 30), LEO (Aug. 5), COM (Aug. 9), VIR (Aug. 17), BOO (Aug. 22), VIR (Aug. 24), LIB (Sep. 6), SCO (Oct. 4), OPH (Oct. 14), SGR (Dec. 4), OPH (1992 Aug. 12), SGR (Oct. 11) Predictions for the return of this comet came from S. Nakano (1987) and B. G. Marsden (1988). Both determined an orbit for the 1986 discovery apparition, using 62 and 65 positions, respectively, and perturbations by all nine planets. Nakano and Marsden then integrated their orbits to this apparition, predicting perihelion dates of 1991 July 22.37 and July 22.61, respectively. The comet passed aphelion on 1988 December 6. During this apparition, it would attain its most southerly declination of 50
on 1990 August 2 and its most northerly declination of +29
on 1991 July 29. The first observations came from K. J. Meech (Cerro Tololo InterAmerican Observatory, Chile), when she acquired eight CCD images 543

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during 1989 April 6.32–6.35 while using the 152-cm reflector. She gave the nuclear magnitude as 22.5. The position on the first image was α = 19h 50.0m, δ = 35
150 (2000). Meech acquired another five images using the same equipment around April 7.38. The comet had reached a minimum elongation of 11
on January 2. Meech remained the only observer during the remainder of 1989 and throughout 1990. At Mauna Kea (Hawaii, USA) in 1989, she used the 224-cm reflector and an R filter to acquire 35 CCD images on June 3 and 23 CCD images on August 1. At Cerro Tololo in 1990, she used the 402-cm reflector and an R1 filter to acquire 25 CCD images on April 29. No physical descriptions were provided for any of these observations. The comet reached a maximum elongation of 162
on 1989 July 5, a minimum elongation of 15
on 1990 January 5, and a maximum elongation of 153
on 1990 July 8. The comet was lost in the Sun’s glare as 1991 began, with a minimum elongation of 20
occurring on January 11. It reached a maximum elongation of 73
on May 21. On the same night, Meech obtained 12 CCD images of the comet while using the 402-cm reflector at Cerro Tololo. She noted, “Very bright. REMARKABLE rotation period! [A] 0.3–0.4 [magnitude] variation in 0.5 hour!” She added that no coma was apparent. A. C. Gilmore and P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) obtained photographs using a 61-cm reflector on July 3, 4, and 5. They estimated the nuclear magnitude as 16 on the first two nights and 14 on the last night. Also on the 5th, Gilmore and Kilmartin reported a faint, narrow tail extending 3000 in PA 207
. The first visual observation was also the last observation prior to the comet’s perihelion passage. G. W. Wolf (New Zealand) used his 6-cm refractor on the 13th, giving the comet’s magnitude as 8.6. He also noted that the coma was slightly condensed and 1.90 across. The comet reached a minimum elongation of 2
on July 21, as it passed perihelion. R. J. Modic (Ohio, USA) tried to observe the comet in strong twilight with his 20-cm reflector on July 24 but was unsuccessful. He concluded the comet was fainter than magnitude 2.5. J. E. Bortle (Stormville, New York, USA) attempted to see the comet in twilight on the 28th, using 20  120 binoculars. No trace was detected, prompting him to conclude that the comet was fainter than magnitude 5.5. Additional attempts by Modic on the 29th and 30th were also not successful. He surmised that the comet was fainter than 6.0 and 8.5, respectively. The comet was finally spotted by A. J. S. Pereira (Cabo da Roca, Portugal) on July 31. He was using a 15-cm reflector. Pereira determined the magnitude as 8.9 and described the coma as moderately condensed and about 50 across. The comet was well observed during the first two weeks of August. D. E. Machholz (Emigrant Gap, California, USA), the original discoverer of this comet back in 1986, observed the comet with his 12-cm refractor on the 1st.

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He judged the magnitude as 8.0 and said the coma was elongated, with an east–west length of 40 and a north–south length of 30 . Also, on the 1st, C. E. Spratt (Victoria, British Columbia, Canada) observed the comet with his 20-cm reflector, giving the magnitude as 8.8 and describing the coma as slightly condensed and 50 across. C. S. Morris (Lockwood Valley, California, USA) saw the comet with his 51-cm reflector on the 4th. He determined the magnitude as 9.0 and said the coma was moderately condensed and 0.80 across. On the 6th, A. Hale (Las Cruces, New Mexico, USA) said the comet was at a low altitude and seen in fairly poor sky conditions. Nevertheless, he gave the magnitude as 9.5 as seen through his 41-cm reflector. He added a “faint coma extension (not quite a tail) to the east was suspected.” Morris next saw the comet on the 10th and 11th, giving the magnitude as 9.6 and 9.8, respectively. He noted the coma was slightly condensed and 1.7–1.80 across. V. L. Korneev (Zelenograd, Russia) provided an excellent series of tail measurements from the 2nd to the 10th, noting lengths of 3-40 and PAs that varied from 290–300
. Modic reported seeing a stellar or nearly stellar central condensation, estimating the magnitude as 11.8 on the 2nd, about 13 on the 12th, and 12.8 on the 13th. The last visual observation was made by Modic on August 14.07. He gave the magnitude as 11.5 and said the coma was slightly condensed and 1.30 across. The final astrometric positions were acquired by E. F. Helin, S. Cohen, K. J. Lawrence, and P. Rose (Palomar Observatory, California, USA), when they exposed films on the comet’s predicted position during August 14.17–14.18, using the 46-cm Schmidt telescope. They estimated the magnitude as 10. The position on the last image was α = 12h 39.4m, δ = +17
250 (2000). The comet’s elongation from the Sun had been steadily increasing since passing perihelion in late July; however, after reaching a maximum of only 58
on September 7, it began to decrease. Modic and Hale attempted to find the comet in early September but were unsuccessful. Modic’s attempts came on the 1st, 2nd, 5th, and 7th, using both his 36-cm and 40-cm reflector. He concluded the comet was fainter than 13.3–13.7. Hale looked for the comet with his 41-cm reflector on the 2nd and concluded it must have been fainter than 13.0. No further observations were attempted during the remainder of the year. The comet reached a minimum elongation of 3
on December 24. The comet was actually observed in 1992 by Meech. She acquired six CCD images on March 7 while using the 402-cm reflector at Cerro Tololo. The comet reached a maximum elongation of 176
on June 27. Meech and T. L. Farnham used the 224-cm reflector on Mauna Kea to obtain 11 CCD images on August 2, 23 CCD images on August 3, 20 CCD images on August 4, and 37 CCD images on August 6. The 6th also marked the final time the comet was detected during this apparition, with the total exposure time being 11,100 seconds during August 6.30–6.45. The comet’s predicted

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position on the last image was α = 17h 47.7, δ = 28
270 (2000). The comet reached a minimum elongation of 6
on December 29. During the remainder of this comet’s apparition, it reached a maximum elongation of 168
on 1993 July 1 and a minimum elongation of 10
on 1994 January 1. The comet passed aphelion on 1994 March 4. Multiple apparition orbits have been calculated by D. W. E. Green (1989), B. G. Marsden (1991, 1993, 2005), K. Muraoka (1991), P. Rocher (1997), Nakano (1998, 2003, 2004, 2007, 2009, 2014), and K. Kinoshita (2003, 2007, 2012). All of these calculations included full planetary perturbations, while only those published from 1997 onward, except for Nakano (1998), solved for nongravitational effects. The result was a perihelion date of July 21.98 and a period of 5.24 years. The nongravitational terms were within the following ranges: A1 = 0.04 to +0.02 and A2 = 0.0002 to 0.0001. The orbit of Nakano (2014) is given below. T ω Ω (2000.0) i q e 1991 Jul. 21.9821 (TT) 14.5362 94.5176 60.1461 0.125545 0.958370

absolute magnitude: H0 = 11.7, n = 2.8, from visual observations (Meyer) full moon: Nov. 23, Dec. 23, 1989 Jan. 21, Feb. 20, Mar. 22, Apr. 21, May 20, Jun. 19, Jul. 18, Aug. 17, Sep. 15, Oct. 14, Nov. 13, Dec. 12, 1990 Jan. 11, Feb. 9, Mar. 11, Apr. 10, May 9, Jun. 8, Jul. 8, Aug. 6, Sep. 5, Oct. 4, Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30, Apr. 28, May 28, Jun. 27, Jul. 26, Aug. 25, Sep. 23, Oct. 23, Nov. 21, Dec. 21, 1992 Jan. 19, Feb. 18, Mar. 18, Apr. 17, May 16, Jun. 15, Jul. 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6, Mar. 8, Apr. 6, May 6, Jun. 4, Jul. 3, Aug. 2, Sep. 1, Sep. 30, Oct. 30, Nov. 29, Dec. 28, 1994 Jan. 27, Feb. 26, Mar. 27 sources: S. Nakano, Nakano Note, No. 495 (1987 Aug. 20); B. G. Marsden, MPC, No. 13042 (1988 May 1); K. J. Meech and D. W. E. Green, MPC, Nos. 14669–70, 14748 (1989 Jul. 18); K. J. Meech, MPC, No. 16295 (1990 Jun. 8); K. J. Meech, MPC, No. 16935 (1990 Oct. 4); A. C. Gilmore, P. M. Kilmartin, and B. G. Marsden, IAUC, No. 5301 (1991 Jul. 9); A. J. S. Pereira, D. E. Machholz, and C. S. Morris, IAUC, No. 5318 (1991 Aug. 5); K. J. Meech, A. C. Gilmore, P. M. Kilmartin, and B. G. Marsden, MPC, Nos. 18491, 18497, 18598 (1991 Aug. 25); K. Muraoka, Nakano Note, No. 557 (1991 Sep. 4); E. F. Helin, S. Cohen, K. J. Lawrence, and P. Rose, MPC, No. 18666 (1991 Sep. 23); G. W. Wolf, J. E. Bortle, A. J. S. Pereira, C. E. Spratt, C. S. Morris, A. Hale, and V. L. Korneev, ICQ, 13 (1991 Oct.), pp. 150, 165–6; R. J. Modic, ICQ, 14 (1992 Apr.), pp. 33, 42; B. G. Marsden, CCO, 8th ed. (1993), pp. 36, 70; K. J. Meech correspondence with G. W. Kronk (1994); P. Rocher correspondence with G. W. Kronk (1997, 2002); S. Nakano, Nakano Note, No. 690 (1998 Jul. 27); S. Nakano, CCO, 15th ed. (2003), pp. 102–3; K. Kinoshita correspondence with G. W. Kronk (2003, 2007, 2012); S. Nakano, Nakano Note, No. 1044 (2004 Apr. 6); B. G. Marsden, CCO, 16th ed. (2005), 546

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pp. 124–5; S. Nakano, Nakano Note, No. 1466 (2007 Apr. 30); S. Nakano, Nakano Note, No. 1771 (2009 Apr. 22); S. Nakano, Nakano Note, No. 2733 (2014 Jun. 25). 97P/1991 A1 Prediscovery: 1991 January 5.45 (Δ = 1.55 AU, r = 1.59 AU, Elong. = 74
) (Metcalf– Discovered: 1991 January 7.18 (Δ = 1.57 AU, r = 1.59 AU, Elong. = 73
) Brewington) Last seen: 1992 February 5.24 (Δ = 2.80 AU, r = 3.68 AU, Elong. = 149
) Closest to the Earth: 1990 September 16 (1.0427 AU) 1991 I=1991a Calculated path: PSC (Pre), CET (Jan. 13), PSC (Feb. 17), CET (Feb. 19), TAU (Mar. 19), ORI (Apr. 19), TAU (May 13), ORI (May 17), GEM (May 31), CMi (Jul. 3), CNC (Jul. 13), LEO (Sep. 1), HYA (Sep. 7), SEX (Sep. 15), LEO (Nov. 18) Discovered in 1906 by J. H. Metcalf, this comet was next expected at perihelion in 1914 June, although it was not favorably placed for observations. Nevertheless, H. S. Leavitt (Harvard College Observatory, Massachusetts, USA) reported two images of the comet were found on photographs obtained with the 41-cm Metcalf telescope on 1915 February 10. A few days later her colleague, E. C. Pickering, said that the reported comet recovery proved to be images of the minor planet 393 Lampetia. He added that comet Metcalf “has not been found on photographs taken with the Metcalf Telescope with exposures of 1 hour.” For the next return, the predicted perihelion date was given as around 1921 December by A. C. D. Crommelin (1921) and 1922 February 18.5 by H. Mahnkopf (1922). Mahnkopf noted the comet was unfavorably placed for recovery. No observations were reported. G. Merton (1922) took E. Bianchi’s orbit for the 1906 apparition and integrated it forward, applying perturbations by Jupiter. He said the comet passed 0.86 AU from Jupiter on 1911 September 15 and determined the comet’s perihelion dates as 1914 June 11.3, 1922 March 3, and 1929 November 23.5. He said the conditions for recovery had been unfavorable in 1914 and 1922, but would be favorable in 1929. A few observations were attempted in the latter year, with that of A. Schwassmann and A. A. Wachmann (Hamburg Germany) being perhaps the most ambitious. They obtained a four-hour exposure on a 30-cm by 30-cm glass plate of the comet’s predicted position on the night of 1929 September 11/12, using the 34-cm Lippert-Astrograph. Although four minor planets were found, there was no trace of the comet. [Following this comet’s recovery in 1991, astronomers were able to establish the actual perihelion dates for the above years, giving them as 1914 June 7.6, 1922 March 5.0, and 1929 November 29.7.] V. V. Emel’yanenko, N. Y. Goryajnova, and N. A. Belyaev (1974) redetermined this comet’s orbit for the 1906 apparition, using 73 positions, and then integrated the motion to 1976 by applying perturbations by Venus to Saturn. They noted three close approaches to Jupiter: 1911 September (0.86 AU), 1935 August (1.17 AU), and 1969 August (1.05 AU). They concluded 547

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that the comet would probably pass perihelion on 1975 June 20.92, but added that this “was necessarily somewhat uncertain.” The apparition was not favorable and the comet was not expected to become brighter than magnitude 18. No observations were apparently attempted. [As with the earlier predictions above, a more accurate perihelion date was determined following the comet’s 1991 recovery. It was 1975 June 23.0.] H. J. Brewington (Cloudcroft, New Mexico, USA) was nearing the end of a three-hour comet-hunting session with his 41-cm reflector, when he discovered this comet on 1991 January 7.18. He gave the magnitude as 9.8 and said the comet appeared diffuse, with a strong condensation. He told an Associated Press reporter (published in the Albuquerque Journal), “It looked like a cotton ball with a real bright condensed center.” The comet’s position was α = 0h 08.5m, δ = 6
000 (2000). Brewington detected motion in about 15 minutes and immediately notified the Central Bureau for Astronomical Telegrams (CBAT). CBAT immediately sent out a request for confirmation. In response, A. Hale (Kitt Peak National Observatory, Arizona, USA) confirmed the comet on January 7.24 using his 20-cm reflector. Hale said the comet was then at a very low altitude and the atmosphere was very damp, but he judged the comet’s magnitude as 9.3. The official announcement of “Comet Brewington (1991a)” was sent out to the world by CBAT on January 7; however, two other messages were received from amateur astronomers who had independently discovered this comet. T. Kiuchi (Usuda, Nagano, Japan) found the comet on January 7.48 using 25  150 binoculars, while W. A. Bradfield (near Adelaide, South Australia, Australia) located the comet on January 7.53 during one of his routine comet searches. Both observers estimated the magnitude as 9. Two additional amateur astronomers reported confirmation of this comet within hours of the original confirmation request. T. Ohtsuka (Chiyoda, Gunma, Japan) acquired a photograph with a 300-mm telephoto lens on January 7.44, estimating a magnitude of 8.5, while P. Camilleri (Cobram, Victoria, Australia) saw the comet with 20  80 binoculars on January 7.48, giving the magnitude as 9.5. Camilleri also reported a moderately condensed coma 30 across. B. G. Marsden announced on January 9 that five precise positions received for the period of January 7–9 revealed orbital elements that “strongly resemble those of P/Metcalf” of 1906. He also noted that an unpublished prediction by R. J. Buckley in 1975 represented the current positions within 1
and that an adjustment of only 1.8 days in the perihelion date “reduces the residuals to 10 .” The comet officially became known as “Metcalf-Brewington.” In an e-mail published in The Astronomer Electronic Circular number 475 on January 10, R. H. McNaught (Siding Spring Observatory, New South Wales, Australia), commented that the orbit indicated the comet was slowly fading, “so the circumstance of 3 discoveries in 8.5 hours clearly indicated an outburst.” On January 11, McNaught and his colleague, 548

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C. J. Grillmair, indicated that, based on the present brightness, the comet should have been visible on a photographic plate obtained by M. Hartley with the 122-cm Schmidt telescope on 1990 June 4.8; however, although the photographic plate revealed stars as faint as R magnitude 19, no trace of the comet was found. On January 18, International Astronomical Union Circular number 5168 reported that M. Tanaka (Iwaki, Fukushima, Japan) reported a prediscovery observation on photographs acquired with a 30-cm reflector on 1991 January 5.5. He estimated the magnitude as about 15. D. W. E. Green stated that this suggests “a significant outburst took place within two days of Brewington’s discovery.” In addition, R. W. Panther (England) reported in the 1991 February issue of The Astronomer that he had swept the western and northwestern sky for 1.25 hours on January 3, as part of a routine search for comets. He said a 9th-magnitude comet would not have been missed. The comet was well observed during the remainder of January. McNaught obtained a 10-minute exposure on hypered Kodak Technical Pan 4415 film using the 51-cm Uppsala Southern Schmidt on January 8. He described the comet as diffuse and 20 across, exhibiting a bright, narrow tail 10 long and a much fainter, narrow tail 1.0
long. Both extended toward PA 70
. On the same night, J. E. Bortle (Stormville, New York, USA) visually observed the comet with 10  50 binoculars, giving the magnitude as 8.4 and the coma diameter of 5.50 . He indicated that the coma was moderately condensed. Bortle said his 32-cm reflector “showed a well-condensed coma composed of what seemed to be a double envelope of material.” Furthermore, a Swan-band filter revealed no change in brightness. This indicated the comet was “very dusty”. Bortle said all of this “smacked of an object undergoing a major outburst.” D. A. J. Seargent (The Entrance, New South Wales, Australia) saw the comet using 15  80 binoculars on the 9th and 11th, giving the magnitude as 8.4 and 8.5, respectively. On the first night, he reported a well-condensed coma about 40 across, as well as a tail extending 40 in PA 70
. C. S. Morris (Pine Mountain Club, California, USA) observed on the 11th and 13th, using 20  80 binoculars. On both nights, he determined the magnitude as 8.4 and reported a moderately condensed coma about 80 across. Morris saw a tail on the second night, noting that it extended 30’ in PA 70
. Using his 25-cm reflector on the 15th, R. J. Bouma (Groningen, Netherlands) gave the magnitude as 8.7. He said the coma was 3.50 in diameter, while a tail extended 210 in PA 63
. Observations by Bortle on the 17th and 19th revealed the magnitude as 8.6 and 8.7, respectively. He suspected a tail extending toward PA 70
on the latter date. Morris also saw the comet on the 19th. He gave the magnitude as 8.7 and said the tail extended 30’ in PA 80
. On the 23rd, Hale observed with his 41-cm reflector and judged the magnitude as 9.6. He said “the comet appears fainter and more diffuse than before.” Bouma saw the comet on the 31st, giving the magnitude as 9.5. He added that the coma appeared slightly condensed and 3.50 across. 549

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The comet continued to fade in February. Bortle saw it with 20  80 binoculars on the 2nd and 4th, giving the magnitude as 8.9 and 9.1, respectively. He noted the coma was 4.90 across on the first night and 5.30 across on the second night. Bortle also examined the comet using his 32-cm reflector. He said the comet seemed “slightly enhanced” when the Swan-band filter was used on the 2nd. He also remarked, “coma seems rather suddenly condensed near center – no nucleus.” On the 4th, Bortle wrote, “coma is noticeably condensed toward the center; small brightness plateau at heart of coma; no nucleus at 110.” Using his reflector, Bortle determined the magnitude as 10.1 on the 12th and noted the coma was about 2.60 across. Bouma was using his 25-cm reflector on the 2nd and 4th and reported that the comet faded from 9.6 to 9.8. He said the coma was very weakly condensed and 2.5–30 across. Using his 41-cm reflector, Hale gave the magnitude as 9.4 on the 5th, 9.5 on the 14th, and 9.7 on the 22nd. Observations continued to dwindle in March as the comet continued to fade. Hale determined the magnitude as 10.2 on the 4th and 10.6 on the 15th. On the first night, he noted, “Comet more vague and diffuse than before.” On the second night, he said the “comet is very large and diffuse.” Morris said the magnitude was 10.8 on the 9th, while the coma was 2.60 across. R. J. Modic (Ohio, USA) saw the comet while using his 36-cm and 40-cm reflectors on the 15th and 17th. He noted the magnitude faded from 11.5 to 11.7. Because of the continued decline in brightness, the comet was becoming more difficult to see in April, especially since its elongation from the Sun had dropped below 50
. Modic tried to see the comet with his 40-cm reflector on the 3rd but was unsuccessful. He concluded the comet must have been fainter than magnitude 12.5. However, G. W. Kronk (Troy, Illinois, USA) managed to see the comet on the 6th, using his 33-cm reflector, and estimated the magnitude as 11.1. He reported the coma was only slightly condensed and 0.50 across. The final astrometric position was obtained by T. Seki (Geisei, Kochi, Japan) when he photographed the comet with his 60-cm reflector on April 3.47. He estimated the magnitude as 16. The position was α = 4h 02.3m, δ = +10
350 (2000). No further observations were made during the remainder of the year. After having moved northward since its discovery, the comet attained its most northerly declination of +14
on May 28. The comet reached a minimum elongation of 8
on July 30. After having moved southward since last July, the comet attained a declination of 4
on 1992 January 4 and then began a northward motion. The final observations of this comet were obtained during February 3.30, February 4.33–4.35, and February 5.22–5.24, using the 154-cm reflector at La Silla Observatory (Chile). J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton (2000) analyzed these images as part of a program to study cometary nuclei. They said the comet appeared as a “faint 550

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stellar object” on all images, although a “faint coma” was noted on the 4th and 5th. The V magnitude was given as 22.0 on the 3rd and 22.6–22.7 on both the 4th and 5th. Finally, they determined that the nucleus has a radius of 1.4 kilometers. The predicted position on the last image was α = 10h 54.3m, δ = 2
200 (2000). Multiple apparition orbits have been calculated by S. Nakano (1991, 1998, 2001, 2008, 2011), G. Sitarski (1992), P. Rocher (1999, 2001, 2013), and K. Kinoshita (2003, 2011). All of these calculations included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of 1991 January 5.61–5.63 and a period of 7.76 years. The orbits published during 1991–2008 included positions from 1906 and produced nongravitational terms within the following ranges: A1 = +0.41 to +0.68 and A2 = +0.0595 to +0.0657. Sitarski solved for three nongravitational terms, giving them as A1 = +0.38, A2 = +0.0600, and A3 = 0.10. The orbits published from 2011–2013 included positions from the 1991, 2001, and 2011 apparitions. The nongravitational terms were given as A1 = 1.17 and A2 = 1.4335 by Nakano (2011), A1 = 0.37 and A2 = 1.5329 by Kinoshita (2011), and A1 = 2.57 and A2 = 1.4147 by Rocher (2013). It should be noted that Rocher (2013) included the relativity effect of the Sun, which produced smaller residuals. His orbit is given below. T ω Ω (2000.0) i q e 1991 Jan. 5.6207 (TT) 208.0445 187.7885 13.0284 1.591478 0.593948

absolute magnitude: H0 = 4.1, n = 5.9 (Kidger, 1993) full moon: 1990 Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30, Apr. 28 sources: H. S. Leavitt, HCOB, No. 575 (1915 Feb. 17); E. C. Pickering, HCOB, No. 578 (1915 Feb. 23); H. S. Leavitt and J. H. Metcalf, Nature, 94 (1915 Feb. 25), p. 708; H. S. Leavitt, J. H. Metcalf, and E. C. Pickering, Nature, 95 (1915 Mar. 4), p. 17; A. C. D. Crommelin, The Observatory, 44 (1921 Feb.), p. 62; G. Merton, MNRAS, 82 (1922 Apr.), pp. 381–2; H. Mahnkopf, AN, 216 (1922 Jul. 21), p. 91; G. Merton, BAA Handbook for 1929 (1928 Nov.), p. 33; G. Merton, PA, 37 (1929 Aug.-Sep.), p. 405; V. V. Emel’yanenko, N. Y. Goryajnova, and N. A. Belyaev, BAA Handbook for 1975 (1974 Oct.), pp. 73–4; V. V. Emel’yanenko, N. Y. Goryajnova, and N. A. Belyaev, IAUC, No. 2780 (1975 May 15); V. V. Emel’yanenko, N. Y. Goryajnova, and N. A. Belyaev, QJRAS, 19 (1978 Mar.), p. 78; A. Hale, ICQ, 13 (1991 Jan.), pp. 8, 61; H. J. Brewington and A. Hale, IAUC, No. 5155 (1991 Jan. 7); T. Kiuchi and W. A. Bradfield, IAUC, No. 5159 (1991 Jan. 8); H. J. Brewington, Albuquerque Journal (1991 Jan. 8), p. 3E, col. 1–5; T. Ohtsuka, B. G. Marsden, R. J. Buckley, J. E. Bortle, and D. A. J. Seargent, IAUC, No. 5160 (1991 Jan. 9); T. Ohtsuka, R. H. McNaught, B. G. Marsden, and R. J. Buckley, TAEC, No. 475 (1991 Jan. 10); R. H. McNaught, C. J. Grillmair, and M. Hartley, IAUC, No. 5162 (1991 Jan. 11); D. A. J. Seargent and C. S. Morris, IAUC, No. 5166 (1991 Jan. 17); M. Tanaka and 551

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D. W. E. Green, IAUC, No. 5168 (1991 Jan. 18); M. Tanaka and T. Ohtsuka, MPC, No. 17492 (1991 Jan. 30); R. W. Panther, The Astronomer, 27 (1991 Feb.), p. 210; H. J. Brewington and J. E. Bortle, ST, 81 (1991 Apr.), p. 447; J. E. Bortle, D. A. J. Seargent, C. S. Morris, and P. Camilleri, ICQ, 13 (1991 Apr.), pp. 72, 83–4; T. Seki, MPC, No. 18166 (1991 May 28); A. Hale and R. J. Modic, ICQ, 13 (1991 Jul.), pp. 96, 132–3; S. Nakano, Nakano Note, No. 551 (1991 Aug. 8); S. Nakano, MPC, No. 18597 (1991 Aug. 25); G. Sitarski, AcA, 42 (1992), pp. 49–57; G. W. Kronk, ICQ, 14 (1992 Oct.), p. 120; M. R. Kidger, EM&P, 63 (1993 Dec.), pp. 179–85; R. J. Bouma, ICQ, 16 (1994 Apr.), p. 67; S. Nakano, Nakano Note, No. 674 (1998 Apr. 30); P. Rocher correspondence with G. W. Kronk (1999, 2001, 2013); J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton, Icarus, 147 (2000 Sep.), pp. 164–5, 174; S. Nakano, CCO, 14th ed. (2001), pp. 92–3; K. Kinoshita correspondence with G. W. Kronk (2003, 2011); S. Nakano, Nakano Note, No. 1608 (2008 May 5); S. Nakano, Nakano Note, No. 2168 (2011 Nov. 26). C/1991 A2 (Arai) Prediscovery: 1990 November 18.09 (Δ = 1.22 AU, r = 1.47 AU, Elong. = 83
) Discovered: 1991 January 5.63 (Δ = 0.54 AU, r = 1.48 AU, Elong. = 151
) 1990 Last seen: 1991 March 13.92 (Δ = 1.56 AU, r = 1.93 AU, Elong. = 95
) XXVI=1991b Closest to the Earth: 1991 January 9 (0.5328 AU) Calculated path: PYX (Pre), HYA (Dec. 10), CNC (1991 Jan. 3), LYN (Jan. 15), CAM (Feb. 3), LYN (Feb. 4), CAM (Feb. 6) In the course of his comet survey, M. Arai (Yorii, Saitama, Japan) photographically discovered this comet on 1991 January 5.63, using an automated 16-cm reflector that was controlled by an Apple II computer. The comet was found near the edge of an overexposed frame of Kodak Technical Pan 2415 film that was exposed for 10 minutes. The magnitude was estimated as 12 and the position was α = 8h 57.2m, δ = +11
580 (2000). An additional exposure using the same film and equipment was acquired an hour later. Arai had exposed about 30 thousand films before he discovered this comet. Arai acquired confirmation exposures on January 6.62 and January 6.63, using a 30-cm hyperboloid astrocamera. The comet was described as diffuse and centrally condensed. Several independent confirmations were made on January 7. R. H. McNaught (Siding Spring Observatory, New South Wales, Australia) photographed the comet using the 51-cm Uppsala Southern Schmidt telescope on January 7.51 and January 7.67. He estimated the magnitude as 10 and said the strongly condensed comet exhibited a coma 20 across. Y. Kushida and R. Kushida (Yatsugatake South Base Observatory, Hokuto, Yamanashi, Japan) photographed the comet on January 7.53 and January 7.55 using a 20-cm reflector and estimated the magnitude as 10. Arai acquired photographs on January 7.62 and January 7.63 and estimated the magnitude as 11. T. Seki (Geisei, Kochi, Japan) photographed the comet on January 7.76 and estimated the magnitude as 9.5. R. W. Panther (England) 552

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visually observed the comet on January 7.96 using his 20-cm reflector. He gave the magnitude as 11.7 and noted a very slightly condensed coma 60 across. The first prediscovery image was found less than two weeks after the comet was discovered. The trail was located on a five-minute exposure acquired by T. Ohtsuka and T. Kojima (Tatebayashi, Gunma, Japan) on 1990 December 23.65. The magnitude was estimated as 10. During the apparition of comet C/1996 B2 (Hyakutake), the X-ray spacecraft Röntgensatellit (ROSAT) discovered unexpectedly bright X-ray emission from the comet. This prompted a search for more comets in ROSAT data, starting with the whole sky X-ray survey that was performed by the satellite during 1990 and 1991. K. Dennerl, J. Englhauser, and J. E. Trümper (Max Planck Institute for Extraterrestrial Physics, Garching, Germany) located observations of comet C/1991 A2 (Arai) during the period of 1990 November 18.09–21.43. During that period, the comet was about 1.2 AU from the Earth and 1.5 AU from the Sun and, assuming that it held to the brightness parameters derived during its period of observability, would have had a magnitude of 12 or fainter. That made it the optically faintest comet detected in X-rays at that time. The comet faded during the remainder of January. A. Hale (Las Cruces, New Mexico, USA) and D. H. Levy (Tucson, Arizona, USA) observed the comet on the 8th, using their 41-cm reflectors. The magnitude was given as 10.4 by Hale and 10.8 by Levy. Levy added that the coma was diffuse and 80 across. The comet was seen by P. Birtwhistle (England) on the 9th, using 20  80 binoculars. He judged the magnitude as 9.7 and reported a very slightly condensed coma 60 across. Hale and C. S. Morris (Pine Mountain Club, California, USA) saw the comet on the 11th. The magnitude was determined as 9.9 by Hale and 10.3 by Morris. Morris was using his 26-cm reflector and reported a very slightly condensed coma 50 across. He added that the addition of a Swan-band filter revealed the coma diameter as 70 . R. J. Bouma (Groningen, Netherlands) was one of the most prolific observers during the month, as he saw the comet on seven nights spanning the 10th to the 31st. He was using his 25-cm reflector and reported the comet faded from magnitude 9.9 to 11.3. Bouma indicated that the coma diameter varied from 2.5–3.50 , while it appeared slightly condensed on the 10th and completely uncondensed by the 31st. Another prolific observer was M. Möller (Germany), who also saw the comet on seven nights. His observations spanned the period of the 12th to the 19th and he used a 15-cm reflector. Möller indicated the comet faded from 10.3 to 11.0, while the coma diameter generally decreased from 2.50 to 1.50 . H. Mikuz (Ljubljana, Slovenia) obtained a couple of CCD images of the comet around the middle of January using a 20-cm Baker-Schmidt telescope. A 120-second exposure on the 16th revealed a coma 2.40 across, a central condensation 1.10 across, and a straight, narrow tail extending 3.50 in PA 226
. A 90-second exposure on the 19th revealed a coma 2.40 across, 553

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a central condensation 0.80 across, but no tail. The comet reached a maximum elongation of 165
on January 14. Observations dwindled in February, as the comet continued to fade. A. Nakamura (Kuma, Ehime, Japan) and Bouma saw the comet on the 2nd. Nakamura was using his 20-cm reflector and determined the magnitude as 11.2. He reported a slightly condensed coma 30 across. Bouma judged the magnitude as 11.1 and noted an uncondensed coma 3.50 across. Another observation by Nakamura on the 3rd revealed a magnitude of 11.3, as well as an uncondensed coma 30 across. On the 4th, Bouma determined the magnitude as 11.2 and the coma diameter as 3.50 . Hale gave the magnitude as 11.3 on the 5th. Nakamura judged the magnitude as 11.8 on the 8th, noting a coma 2.50 across. Morris observed the comet on the 9th and 10th, giving the magnitude as 11.2 and 11.3, respectively. He described the coma as only slightly condensed and 40 across. The final visual observations were made by Nakamura on the 12th and 17th. On the first night, he gave the magnitude as 12.0 and said the coma was uncondensed and 20 across. On the second night, he gave the magnitude as 12.6 and the coma diameter as 1.50 . The comet was last detected on March 13.88 and March 13.92, when E. Meyer, E. Obermair, and H. Raab (Davidschlag, Austria) obtained photographs using a 29-cm reflector. They used Kodak Technical Pan 2415 film and estimated the magnitude of the comet as 15.5. The position on the final photograph was α = 6h 07.5m, δ = +70
190 (2000). The first orbit was calculated by S. Nakano and was published on 1991 January 8. Nakano used nine positions from January 6–8 and determined a parabolic orbit with a perihelion date of 1990 December 12.08. Nakano published a revised parabolic orbit on January 18 that used 19 positions from 1990 December 23 to 1991 January 12. The result was a perihelion date of December 11.07. The first elliptical orbit was calculated by Nakano and was first published on February 28. Nakano used 59 positions from 1990 December 23 to 1991 February 13 and included perturbations by all nine planets. The result was a perihelion date of December 10.88 and a period of about 1822 years. B. G. Marsden calculated an elliptical orbit that was published on April 28. He used 55 positions from 1990 December 23 to 1991 March 13 and included perturbations by all nine planets. The result was a perihelion date of December 10.89 and a period of about 1857 years. This orbit is given below. T ω Ω (2000.0) i q e 1990 Dec. 10.8873 (TT) 337.6388 115.5226 70.9783 1.434161 0.990507

absolute magnitude: H0 = 10.3, n = 3.1 (Kronk) full moon: 1990 Nov. 2, Dec. 2, Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30 sources: A. Hale, ICQ, 13 (1991 Jan.), pp. 7, 58; M. Arai and R. H. McNaught, IAUC, No. 5157 (1991 Jan. 7); Y. Kushida, R. Kushida, T. Seki, 554

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S. Nakano, and D. H. Levy, IAUC, No. 5158 (1991 Jan. 8); T. Ohtsuka, T. Kojima, and S. Nakano, IAUC, No. 5170 (1991 Jan. 18); T. Ohtsuka, T. Kojima, M. Arai, R. H. McNaught, Y. Kushida, M. Arai, T. Seki, and S. Nakano, MPC, Nos. 17492–3, 17596 (1991 Jan. 30); S. Nakano, MPC, No. 17791 (1991 Feb. 28); S. Nakano, IAUC, No. 5202 (1991 Mar. 1); C. S. Morris, M. Möller, and H. Mikuz, ICQ, 13 (1991 Apr.), pp. 71, 79–80; E. Meyer, E. Obermair, H. Raab, and B. G. Marsden, MPC, Nos. 18012, 18081 (1991 Apr. 28); A. Hale, ICQ, 13 (1991 Jul.), pp. 127–8; R. W. Panther, ICQ, 13 (1991 Oct.), p. 163; A. Nakamura, ICQ, 14 (1992 Jan.), p. 19; R. J. Bouma, ICQ, 16 (1994 Apr.), p. 42; P. Birtwhistle, ICQ, 17 (1995 Jul.), p. 141; K. Dennerl, J. Englhauser, and J. E. Trümper, IAUC, No. 6472 (1996 Sep. 11); M. Arai, S. Nakano correspondence with G. W. Kronk (2011); H. Raab correspondence with G. W. Kronk (2015). 64P/Swift– Recovered: 1991 January 7.39 (Δ = 1.95 AU, r = 1.47 AU, Elong. = 47
) Gehrels Last seen: 1992 February 5.30 (Δ = 2.78 AU, r = 3.64 AU, Elong. = 145
) Closest to the Earth: 1990 August 18 (1.5875 AU) 1991 II=1991c Calculated path: AQR (Rec), PSC (Jan. 20), ARI (Mar. 16), TAU (Apr. 13), GEM (May 28), CNC (Jul. 12), LEO (Aug. 22), SEX (Oct. 19), LEO (Oct. 25) A prediction for this return was published by S. Nakano (1987, 1988). He used 47 positions from the 1972 and 1981 apparitions and included full planetary perturbations. He then integrated the comet’s motion to this apparition and predicted the comet would pass perihelion on 1991 February 22.68. T. Seki (Geisei, Kochi, Japan) recovered this comet on 1991 January 7.39 and January 7.42, when he obtained photographs of the predicted position using his 60-cm reflector. He estimated the brightness as magnitude 16.5 and noted the comet was diffuse, with a central condensation. The position on the first photograph was α = 22h 14.6m, δ = 5
160 (2000). Seki obtained additional photographs of the comet on January 12.41, January 13.39, and January 13.42, before announcing his recovery. From these photographs, he estimated the magnitude as 17.0. No professional observatories followed this comet during the remainder of January or during the following two months. A. Hale (Las Cruces, New Mexico, USA) made several attempts to visually locate the comet using his 41-cm reflector. From his unsuccessful attempt on January 14, he estimated that the comet must have been fainter than magnitude 13.0. His unsuccessful attempts on February 5 and 14, as well as on March 4, led him to conclude that the comet was fainter than magnitude 12.5. Hale finally spotted the comet on March 13 and 17, giving the magnitude as 12.4 and 12.5, respectively. The last astrometric positions of this comet were obtained during April 2.44–2.45, when Seki obtained three photographs. He estimated the magnitude as 16, while the position was α = 2h 49.2m, δ = +22
080 (2000) on the 555

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last date. The last visual observations were obtained on April 6.16 and April 13.16, when C. S. Morris (California, USA) observed the comet using his 26-cm reflector. He estimated the magnitude as 12.5 on each date and noted the comet was slightly condensed. The coma diameter was given as 1.00 on the last date. The comet attained its most northerly declination of +27
on May 16 and then reached a minimum elongation of 0.7
on July 31. It attained its most southerly declination of 1
on 1992 January 19. The comet was last detected on 1992 February 5.30, when astronomers at La Silla Observatory (Chile) acquired a CCD image using the 154-cm reflector. J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton (2000) analyzed these images as part of a program to study cometary nuclei. They said the comet appeared “star-like” with a V magnitude of 22.1. They determined the radius of the nucleus as 1.5 kilometers and added that the comet was “dynamically old.” The predicted position was α = 11h 14.8m, δ = 1
070 (2000). Multiple apparition orbits have been calculated by S. Nakano (1991, 1997, 2001, 2006, 2009), K. Kinoshita (1998, 2001, 2003, 2010), and P. Rocher (2013). These calculations included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of February 22.72–22.73 and a period of 9.21 years. The nongravitational effects are dependent upon the apparitions used and break down into three distinct groups. These indicate that the radial (A1) and transverse (A2) acceleration parameters are steadily decreasing and increasing, respectively, as the comet ages. The calculations published during 1991–1998 included positions from the 1889, 1972, 1981, and 1991 apparitions. The nongravitational terms were within the following ranges: A1 = +0.56 to +0.57 and A2 = +0.0212 to +0.0220. Nakano (1991, 1997) also provided the normal (A3) acceleration parameter in the following ranges: A3 = 0.02 to +0.07. The calculations published during 2001–2006 included positions from the 1972, 1981, 1991, and 2000 apparitions. The nongravitational terms were within the following ranges: A1 = +0.24 to +0.27 and A2 = +0.0254 to +0.0258. The calculations published during 2009–2013 included positions from the 1981, 1991, 2000, and 2009 apparitions. The nongravitational terms were within the following ranges: A1 = +0.09 to +0.28 and A2 = +0.0379 to +0.0391. Rocher (2013) also included the relativity effect of the Sun. His orbit is given below. T ω Ω (2000.0) i q e 1991 Feb. 22.7300 (TT) 84.8205 314.4427 9.2547 1.355101 0.691616

absolute magnitude: H10 = 9.5, from visual observations (Meyer) full moon: Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30, Apr. 28 sources: S. Nakano, Nakano Note, No. 512 (1987 Aug. 20); S. Nakano, MPC, No. 13045 (1988 May 1); S. Nakano, BAA Handbook for 1991 556

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(1990 Aug.), p. 77; A. Hale, ICQ, 13 (1991 Jan.), p. 61; T. Seki, IAUC, No. 5164 (1991 Jan. 15); S. Nakano, Nakano Note, No. 546 (1991 Jan. 15); T. Seki, MPC, No. 17493 (1991 Jan. 30); A. Hale, IAUC, No. 5222 (1991 Mar. 25); T. Seki, MPC, No. 18012 (1991 Apr. 28); A. Hale, ICQ, 13 (1991 Jul.), p. 134; C. S. Morris, ICQ, 13 (1991 Oct.), p. 177; S. Nakano, Nakano Note, No. 652 (1997 May 3); K. Kinoshita correspondence with G. W. Kronk (1998, 2001, 2003, 2010); J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton, Icarus, 147 (2000 Sep.), pp. 164–5, 175; S. Nakano, CCO, 14th ed. (2001), pp. 86–7; S. Nakano, Nakano Note, No. 1316 (2006 Apr. 8); S. Nakano, Nakano Note, No. 1804 (2009 Jul. 27); P. Rocher correspondence with G. W. Kronk (2013). C/1991 B1 Prediscovery: 1991 January 13.45 (Δ = 3.54 AU, r = 4.34 AU, Elong. = 140
) (Shoemaker– Discovered: 1991 January 22.43 (Δ = 3.39 AU, r = 4.27 AU, Elong. = 150
) Levy) Last seen: 1993 August 15.24 (Δ = 5.24 AU, r = 6.26 AU, Elong. = 177
) Closest to the Earth: 1992 January 4 (2.4359 AU) 1991 Calculated path: SEX (Pre), HYA (Jan. 22), CNC (Mar. 2), LEO (Jun. 25), XXIV=1991d LMi (Jul. 30), UMa (Sep. 5), COM (Oct. 4), CVn (Oct. 12), BOO (Nov. 17), CrB (Dec. 11), HER (Dec. 26), LYR (1992 Jan. 26), CYG (Feb. 20), VUL (Aug. 12), SGE (Sep. 7), AQL (Sep. 15), AQR (Dec. 17), CAP (1993 Aug. 5) In the course of the Palomar Asteroid and Comet Survey, this comet was discovered by C. S. Shoemaker, E. M. Shoemaker, and D. H. Levy (Palomar Observatory, California, USA) on photographic film exposed using the 46-cm Schmidt telescope during 1991 January 22.43–22.45. The magnitude was estimated as 15.5 and the comet was described as “diffuse with strong condensation and possible hint of a tail.” The position at the beginning of the exposure was α = 9h 41.3m, δ = 2
150 (2000). The comet was confirmed by R. H. McNaught (Siding Spring Observatory, New South Wales, Australia) and T. Seki (Geisei, Kochi, Japan). McNaught photographed the comet on January 28.76, using the 51-cm Uppsala Southern Schmidt telescope. The magnitude was estimated as 15.5 and the comet was described as strongly condensed. Seki photographed the comet on January 29.64 and January 29.67 using his 60-cm reflector. He estimated the magnitude as 16. Prediscovery images of this comet were found at two observatories. In the course of the Palomar Planet-Crossing Asteroid Survey, E. F. Helin, K. J. Lawrence, P. Rose, and R. Bambery (Palomar Observatory) had exposed film with the 46-cm Schmidt telescope during January 13.45–13.47 and January 15.50–15.52. Following the discovery announcement, they found the diffuse trail of this comet on these images and estimated the magnitude as 15.0. M. Koishikawa (Sendai Observatory, Miyagi, Japan) found the comet on film he had exposed using a 300-mm telephoto lens during January 19.65–19.67. He estimated the magnitude as 15. 557

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The comet remained faint in February and only a few observations were reported, including some visual observations. The comet was photographed from three different locations on the 7th. The Shoemakers and Levy estimated the magnitude as 15. Seki estimated the magnitude as 16. A. Sugie (Dynic Astronomical Observatory, Shiga, Japan) used a 25-cm Schmidt telescope and estimated the magnitude as 15. T. Kojima (Chiyoda, Gunma, Japan) photographed the comet on the 12th using a 25-cm reflector and estimated the magnitude as 15. The visual observations were made by A. Hale (Las Cruces, New Mexico, USA) on the 15th and 21st, using his 41-cm reflector. He determined the magnitude as 13.7 on both nights. Hale described the comet as “small and quite condensed,” on the first night, adding, “Its appearance is little more than that of a fuzzy star.” The comet reached a maximum elongation of 167
on February 13. The comet showed very little change in brightness during the period of March into June. C. S. Morris (Pine Mountain Club and Lockwood Valley, California, USA) and Hale were the only visual observers to follow the comet throughout these months. Morris used his 26-cm and 51-cm reflectors, noting that the comet slowly brightened from 13.7 on March 9 to 13.3 by June 2. He then noted a magnitude of 13.4 on June 8. The coma remained slightly condensed, with a diameter of 0.7–1.10 , trending toward a slow increase. Hale used his 41-cm reflector, giving the magnitude as 13.6 on March 13 and April 4, 13.7 on April 11 and May 2, and 13.6 on May 14 and June 4. With respect to the May 2 observation, Hale admitted that he “possibly observed” the comet, noting interference from cirrus clouds. No observations were made during the next few months, as the faint comet moved into evening twilight. After reaching a minimum elongation of 19
on August 16, it slowly moved into the morning sky. V. L. Korneev (Zelenograd, Russia) was the first person to spot the comet, when he located it with his 25-cm reflector on October 8 and 9. He estimated the magnitude as 12.9 on both nights, noting that the coma was only slightly condensed and 1.4–1.50 across. The only other observer in October was R. J. Modic (Ohio, USA). Using his 36-cm reflector, he estimated the magnitude as 12.8 on the 18th and determined it as 12.6 on the 21st. The coma exhibited slight condensation and was 0.70 across. The comet had clearly brightened and become more readily observable by November. A. Nakamura (Kuma, Ehime, Japan) noted that it was as bright as magnitude 11.8 through his 20-cm reflector on the 4th and Modic determined it as 12.2 on the 5th. Both men noted a moderately condensed coma, with the diameter given as 1.40 by Nakamura and 0.9’ by Modic. D. E. Machholz (Colfax, California, USA) accidentally “discovered” this comet on the morning of November 6 during a routine comet-hunting session. He was using his 25-cm reflector on the back deck of his home, when he came across a diffuse object of magnitude 11.5–12. After detecting movement, he notified the Central Bureau for Astronomical Telegrams (Cambridge, Massachusetts, USA). A couple of hours later, B. G. Marsden 558

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called Machholz and said the comet had been discovered earlier in the year and had just come out of conjunction with the Sun. On the 10th, the magnitude was given as 11.8 by Modic and 11.7 by Nakamura, while the coma diameter was noted as 0.90 and 1.20 , respectively. Morris gave the magnitude as 10.7 on the 12th and reported a slightly condensed coma that was 3.50 across. On the 13th, R. J. Bouma (Groningen, Netherlands) saw the comet using his 25-cm reflector. He judged the magnitude as 10.9 and said the coma was slightly condensed and 1.70 in diameter. Morris obtained another observation on the 16th, essentially noting little change in the comet’s appearance; however, he did report a possible stellar condensation. Modic and Hale saw the comet on the 17th, reporting magnitudes of 11.7–11.8. Modic added that the coma was moderately condensed and 0.800 across. On the 30th, Bouma determined the magnitude as 10.8 and said the coma was moderately condensed and 2.00 across. The comet was most observed during December and January, reaching a maximum elongation of 68
on January 6. Korneev spotted the comet on December 2 and 3, giving the magnitude as 11.3–11.4 and noting a very slightly condensed coma 2.10 across. He continued to report a slightly condensed coma through the remainder of December and all of January. Korneev’s observations indicate a brightening to magnitude 10.2 by January 11, followed by a steady fading to magnitude 11.0 by January 31. Korneev also reported the coma diameter increasing to 4.50 by January 11, after which it decreased to 1.60 by January 31. Bouma also followed the comet through most of this period. He described the comet as magnitude 10.5 on December 6, with a moderately condensed coma 1.80 across. He reported additional magnitudes of 9.8 on December 11, 9.6 on both December 15 and January 11, 10.2 on January 21, and 9.9 on January 22. He gave coma diameters of 2.20 on December 11 and 2.50 on both December 15 and January 11. Bouma indicated that the comet’s condensation became more diffuse through January 22, at which time it was described as slightly condensed. Modic and Morris reported observations of the tail. Modic said it extended 20 in PA 280
on December 11, 20 in PA 305
on December 31, and 0.50 in PA 302
on January 12. Morris reported that the tail extended 60 in PA 300
on December 16. Although the comet was moving away from both the Sun and Earth in February, observers indicated little change in brightness. Nakamura saw the comet with his 20-cm reflector on the 1st, 5th, and 8th, indicating that the comet brightened from magnitude 10.5 to 10.1. He added that the coma was moderately condensed with a diameter of 2.00 on the 1st, 3.00 on the 5th, and 2.80 on the 8th. W. C. Morrison (Canada) observed the comet on three nights using a 15-cm refractor. He reported magnitudes of 10.8 on the 5th and 12th, and 11.0 on the 29th. Morrison indicated that the coma remained slightly condensed throughout this period, giving the diameter as 1.7–1.80 . Hale’s observations indicated magnitudes of 10.8 on the 6th, 10.9 on the 14th, and 10.6 on the 27th. The only observer to report a tail was 559

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S. Garro (France). He was observing the comet on the 2nd using his 20-cm reflector and reported that it extended 7.80 in PA 335
. The comet reached a minimum elongation of 63
on March 12. Comparing the observations from February and March, it is apparent that the comet was fainter in March; however, as the month progressed, there was still no clear trend as to whether it was brightening or fading. Modic gave the magnitude as 11.6 on the 1st and 5th, and 11.7 on the 29th. Morrison gave the magnitude as 11.3 on the 2nd and 11.1 on the 31st. Hale gave magnitudes of 10.9 on the 4th, and 11.6 on both the 11th and 30th. Bouma gave the magnitude as 10.9 on the 7th and 10.8 on the 29th. Modic determined the coma diameter as 0.80 on the 1st and 5th, noting the presence of a stellar condensation on both nights with a magnitude of 13.8 and 13.9, respectively. He noted that the condensation was centered within the coma on the 1st, but offset toward the northwest on the 5th. In addition, Modic saw a sunward fan extending southeastward on the 5th. Morrison determined the coma diameter as 1.60 on the 2nd and 2.40 on the 31st. Bouma gave the coma diameter as 1.60 on the 7th and 1.30 on the 29th. The comet generally faded in April, with observers reporting the coma as slightly to moderately condensed. Nakamura reported that the brightness decreased from 11.2 to 11.9 between the 2nd and 28th. He added that the coma diameter varied from 1.80 to 2.50 from the 2nd to the 13th and was then 1.40 across on the 28th. Modic was using his 36-cm reflector and reported magnitudes of 11.8–11.9 from the 5th to the 13th and then 12.2 on the 29th. He indicated that the coma diameter decreased from 1.00 to 0.70 during the month. Hale determined the magnitude as 11.6 on the 4th and 10th, and then reported it as 12.4 on the 28th. All observers were reporting the comet as fainter than magnitude 12 by May 4 and they also indicated a continued slow fading in May. Bouma was the most prolific observer. He gave the magnitude as 11.8 on the 2nd, said it was variable from 12.1 to 12.3 from the 20th to the 27th, and then noted a magnitude of 12.4 on the 28th. Bouma said the coma diameter varied from 1.20 to 1.50 during the month and showed little condensation. Nakamura’s observations with his 20-cm reflector indicated the comet faded from 11.9 on the 2nd to 12.5 by the 31st, while the coma diameter was given as 1.80 on the 2nd, and 1.00 on the 10th and 31st. Morris observed the comet with his 51-cm reflector on May 31. He determined the magnitude as 12.0 and said the coma was 0.80 across. Morris added that there was a “nearly stellar” condensation. After having moved northward since its discovery, the comet attained its most northerly declination of +43
on May 27. The comet’s slow fading continued in June. Bouma judged the magnitude as 12.6 on the 3rd, and 12.7 on both the 26th and 28th. He gave the coma diameter as 0.8–1.00 and noted only slight condensation. Using his 36-cm reflector, Modic noted that the magnitude varied from 12.9 to 13.1 from the 3rd to the 29th. He said the coma remained slightly condensed, with a diameter of 0.65–0.850 . Morris saw the comet on three occasions using his 560

cometography: a catalog of comets

26-cm reflector. He determined the magnitude as 12.1 on the 20th and 12.2 on both the 27th and 28th. Morris also reported that the coma remained only slightly condensed, giving the diameter as 1.40 on the 20th, 1.90 on the 27th, and 1.60 on the 28th. Modic again reported seeing a stellar central condensation, giving the magnitude as 14.5 on the 28th and 14.6 on the 29th. The comet was still showing signs of fading in July, although some observers indicated that this was erratic. Morris judged the magnitude as 11.9 on the 3rd, 11.5 on the 4th, 11.6 on the 6th, 11.9 on the 25th, and 12.2 on the 26th. In general, he noted that the coma diameter slightly increased from 1.80 to 2.00 during this period, while the condensation became a bit more diffuse. Bouma was the most prolific observer and said the coma continued to show very little condensation. Although he showed a similar variability in the comet’s brightness as what Morris reported, it is possible to group his observations into three distinct segments to provide a more general picture of the comet’s changes during the month. Bouma gave the magnitude as 12.4 on the 2nd and said the coma diameter was 1.40 . From the 6th to the 8th, Bouma noted magnitudes of 12.5–12.6 and coma diameters of 0.9–1.10 . Bouma determined magnitudes of 12.9–13.1 from the 28th to the 30th, giving the coma diameters as 0.8–0.90 . Morris and Modic reported seeing a strong condensation within the coma in early July. Morris simply described it as “nearly stellar” on the 4th. Modic said the condensation was stellar and centralized within the coma, with a magnitude of 15.0. The comet continued to be well placed for observations throughout August, reaching a maximum elongation of 132
on the 17th. Morris reported magnitudes of 11.8 on the 1st and 12.0 on the 2nd. He added that the coma was 2.00 across and showed little condensation. Morris also reported seeing a nearly stellar condensation on the 1st. Modic saw the comet on five occasions during the month. He determined magnitudes of 13.0–13.1 on the 2nd and 6th, 13.1–13.2 on the 20th and 21st, and 13.7 on the 31st. Modic added that the coma remained slightly condensed, while its diameter decreased from 0.750 to 0.400 . Bouma observed the comet on each night from the 3rd to the 7th, giving magnitudes of 12.7–12.9. He also noted very little condensation and gave coma diameters of 0.9–1.40 . Very few visual observations were reported in September and October, as the comet had faded to the point where only observers with larger telescopes could see it. Bouma saw the comet with a 45-cm reflector on September 24 and 25, noting magnitudes of 13.9 and 13.8, respectively. He added that the coma was slightly condensed and 0.5–0.60 across. Nakamura (Kuma Kogen Astronomical Observatory, Ehime, Japan) spotted the comet on September 25 and 27 with the 60-cm reflector. He determined magnitudes of 13.3–13.4 and said the coma was moderately condensed and 0.6–0.70 across. Modic saw the comet on October 2 with a 40-cm reflector. He judged the magnitude as 14.5 and said the coma was slightly condensed 561

cometography: a catalog of comets

and 0.250 across. Modic also reported an almost stellar central condensation of about magnitude 15.2. The last visual observation was reported by Nakamura on October 19. He determined the magnitude as 14.0 and said the coma was slightly condensed and 0.50 across. Observers from three observatories followed the comet in November. T. Kobayashi (Oizumi, Gunma, Japan) acquired CCD images on the 1st, 11th, and 22nd, using a 16-cm reflector. Kojima photographed the comet on the 23rd. R. E. McCrosky and C.-Y. Shao (Oak Ridge Observatory, Massachusetts, USA) acquired CCD images on the 27th and 28th, using the 155-cm reflector. The only physical description came from Kojima, estimating the magnitude as 15. The comet was lost in the Sun’s glare as 1993 began, passing 10
from the Sun on February 12. Thereafter, it entered the morning sky. After having moved southward since late May of last year, the comet attained a declination of 4
41.20 on March 3, slowly moved northward to 4
40.80 by March 20, and then resumed its southward motion. Observers from two observatories resumed observations in July. McCrosky and Shao acquired CCD images on the 18th and 22nd, using the 155-cm reflector, but no descriptive information was provided. The Shoemakers and Levy obtained photographs on the 21st and 24th, using the 46-cm Schmidt telescope. They determined the magnitude as 15.9. The next observations were also the final ones, as McCrosky and Shao acquired two CCD images during 1993 August 15.22–15.24, using the 155-cm reflector. The comet trailed on the first image and appeared weak. The position on the second image was α = 21h 53.2m, δ = 13
360 (2000). Nakamura acquired CCD images on October 8 using the 60-cm reflector; however, no trace was found. He concluded that the comet must have been fainter than about magnitude 18.5 at that time. The first orbit was calculated by S. Nakano and was published on 1991 January 30. This was a parabolic orbit based on eight positions from January 13–29. The perihelion date was determined as 1991 December 29.11. Nakano calculated a revised parabolic orbit that was published on February 28. This used 13 positions from January 13 to February 13 and determined the perihelion date as December 30.62. The first elliptical orbit was calculated by B. G. Marsden and was published on April 28. He used 44 positions from January 13 to April 13 and included perturbations by all nine planets. The result was a perihelion date of December 31.14 and a period of about 6895 years. Nakano and Marsden calculated additional elliptical orbits during the remainder of 1991 and throughout 1992. These eventually established the perihelion date as December 31.18 and the period as about 6500 years. The last orbit calculated for this comet came from Nakano (1993). He took 362 positions from 1991 January 22 to 1992 November 28 and included full planetary perturbations. The result was a perihelion date of December 31.18 and a period of about 6517 years. This orbit is given below. 562

cometography: a catalog of comets T ω Ω (2000.0) i q e 1991 Dec. 31.1804 (TT) 74.3650 145.1295 77.2881 2.265035 0.993508

absolute magnitude: until T  50 d: H0 = 8, n = 2.1, after T 50 d: H0 = 3.7, n = 5.6, from visual observations (Meyer) full moon: Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30, Apr. 28, May 28, Jun. 27, Jul. 26, Aug. 25, Sep. 23, Oct. 23, Nov. 21, Dec. 21, 1992 Jan. 19, Feb. 18, Mar. 18, Apr. 17, May 16, Jun. 15, Jul. 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6, Mar. 8, Apr. 6, May 6, Jun. 4, Jul. 3, Aug. 2, Sep. 1 sources: C. S. Shoemaker, E. M. Shoemaker, D. H. Levy, and R. H. McNaught, IAUC, No. 5175 (1991 Jan. 28); E. F. Helin, K. J. Lawrence, P. Rose, R. Bambery, and M. Koishikawa, IAUC, No. 5177 (1991 Jan. 30); C. S. Shoemaker, E. M. Shoemaker, D. H. Levy, E. F. Helin, K. J. Lawrence, P. Rose, R. Bambery, M. Koishikawa, R. H. McNaught, T. Seki, A. Sugie, and S. Nakano, MPC, Nos. 17687, 17792 (1991 Feb. 28); A. Hale, IAUC, No. 5203 (1991 Mar. 8); C. S. Morris and A. Hale, IAUC, No. 5217 (1991 Mar. 21); C. S. Morris, ICQ, 13 (1991 Apr.), p. 80; B. G. Marsden, MPC, No. 18082 (1991 Apr. 28); S. Nakano, MPC, No. 18256 (1991 May 28); A. Hale and C. S. Morris, IAUC, No. 5292 (1991 Jun. 15); A. Hale, ICQ, 13 (1991 Jul.), pp. 95, 128; C. S. Morris and V. L. Korneev, ICQ, 13 (1991 Oct.), pp. 163–4; T. Kojima, MPC, No. 19068 (1991 Nov. 21); C. S. Morris, ICQ, 14 (1992 Jan.), p. 20; S. Nakano, MPC, No. 19467 (1992 Jan. 19); R. J. Modic and V. L. Korneev, ICQ, 14 (1992 Apr.), pp. 37–8; A. Hale, ICQ, 14 (1992 Jul.), pp. 72–3; B. G. Marsden, MPC, No. 20602 (1992 Aug. 13); S. Garro and R. J. Modic, ICQ, 14 (1992 Oct.), pp. 102, 108; T. Kobayashi, R. E. McCrosky, and C.-Y. Shao, MPC, No. 21158 (1992 Dec. 9); W. C. Morrison, C. S. Morris, and R. J. Modic, ICQ, 15 (1993 Jan.), pp. 4, 20; S. Nakano, MPC, No. 21758 (1993 Mar. 8); A. Nakamura, ICQ, 15 (1993 Apr.), p. 72; T. Kojima, MPC, No. 21981 (1993 May 6); R. E. McCrosky, C.-Y. Shao, C. S. Shoemaker, E. M. Shoemaker, and D. H. Levy, MPC, No. 22439 (1993 Sep. 1); R. E. McCrosky and C.-Y. Shao, MPC, Nos. 22520, 22522 (1993 Sep. 30); R. J. Bouma, ICQ, 16 (1994 Apr.), pp. 42–3; A. Nakamura, ICQ, 20 (1998 Oct.), p. 184; D. E. Machholz correspondence with G. W. Kronk (2015). 129P/1991 C1 Discovered: 1991 February 7.34 (Δ = 1.84 AU, r = 2.83 AU, Elong. = 178
) (Shoemaker– Last seen: 1991 May 5.52 (Δ = 2.66 AU, r = 2.90 AU, Elong. = 93
) Levy 3) Closest to the Earth: 1991 February 6 (1.8395 AU) Calculated path: LEO (Disc), CNC (Feb. 8) 1990 XXVII=1991e In the course of the Palomar Asteroid and Comet Survey, this comet was discovered by C. S. Shoemaker, E. M. Shoemaker, and D. H. Levy (Palomar Observatory, California, USA) on film exposed on 1991 February 7.34 using the 46-cm Schmidt telescope. They estimated the magnitude as 16.5 and 563

cometography: a catalog of comets

described the comet as “moderately diffuse, with a hint of tail to the northwest.” The position was α = 9h 22.9m, δ = +13
150 (2000). Additional images were obtained on February 8.26. The comet reached a maximum elongation of 178
on February 7. An independent confirmation was acquired by S. M. Larson (Catalina Station, Mt. Bigelow, Arizona, USA) on February 8.33, when he acquired a CCD image using the 154-cm reflector and a Cousins R filter. This revealed a tail extending 10 toward PA 298
. Several magnitude estimates were provided during the remainder of February. A. Sugie (Dynic Astronomical Observatory, Shiga, Japan) photographed the comet on the 9th and estimated the magnitude as 17. R. H. McNaught (Siding Spring Observatory, New South Wales, Australia) photographed the comet on the 10th, using the 51-cm Uppsala Southern Schmidt telescope, and estimated the magnitude as 17. On the 10th and the 12th, T. Seki (Geisei, Kochi, Japan) photographed the comet using his 60-cm reflector and estimated the magnitude as 17 on both nights. On the 11th, E. W. Elst and G. Traversa (Haute-Provence Observatory, France) photographed the comet using the 60-cm Schmidt telescope and estimated the magnitude as 18.0. An attempt by A. Hale (Las Cruces, New Mexico, USA) to visually observe the comet on February 21 using his 41-cm reflector was unsuccessful. He concluded that the comet must then have been fainter than magnitude 13.5. The comet attained its most northerly declination of +14
on March 18. D. W. E. Green reported on IAUC 5248 that, “No observations have been reported of this object since February. Further astrometry is therefore requested; significant reports of non-detection would be useful.” Two days later, it was announced that the Shoemakers had photographed the comet on April 14 and 15 using the 46-cm Schmidt telescope. They estimated the magnitude as 17.5 on the first date. Seki estimated the magnitude as 19 on the 30th. The comet was last detected on May 3.47 and May 5.52, when Seki obtained photographs using his 60-cm reflector. He estimated the magnitude as 19 on both nights. The position on the final photograph was α = 9h 17.9m, δ = +12
290 (2000). This comet’s perihelion distance of 2.8 AU and eccentricity of 0.25 introduced a challenge in determining the perihelion date. The first orbit was published by B. G. Marsden on 1991 February 11. He used 11 positions from February 7–11, giving the perihelion date as 1991 February 26.89 and the period as 7.26 years. A revision was published on February 28. Using 16 positions from February 7–17, he determined the perihelion date as February 14.31 and the period as 7.20 years. S. Nakano published an orbit on May 28, which used 21 positions spanning the entire period of visibility. This revealed a perihelion date of 1990 December 12.40 and a period of 7.25 years. Nakano published a revised orbit on December 23. This gave the perihelion date as December 12.76 and the period as 7.25 years.

564

cometography: a catalog of comets

Multiple apparition orbits have been calculated by Marsden (1997, 2005), Nakano (1999, 2001, 2003, 2005, 2014), K. Kinoshita (2000, 2003, 2008, 2013), and P. Rocher (2005). All of these calculations included full planetary perturbations, while only those published from 2003 onward solved for nongravitational effects. The result was a perihelion date of December 13.73–13.77 and a period of 7.25 years. Using positions from the entire 1990 and 1998 apparitions, as well as from the years 2002–2003 of the 2005 apparition, Kinoshita (2003), Nakano (2003), and Marsden (2005) gave nongravitational terms within the following ranges: A1 = 0.84 to 0.75 and A2 = 1.8509 to 1.8460. Nakano (2005), Rocher (2005), and Kinoshita (2008) used positions from the 1990 and 1998 apparitions, as well as the first 4–5 years of the 2005 apparition, while Kinoshita (2013) used positions from the entire 1990, 1998, and 2005 apparitions, as well as most of the pre-perihelion positions from the 2014 apparition, to determine nongravitational terms within the following ranges: A1 = +6.11 to +7.85 and A2 = 2.3492 to 2.3172. Finally, Nakano (2014) chose to determine nongravitational effects based on S. Yabushita’s theory of sublimating carbon monoxide (or molecular nitrogen). He gave the terms as Y1 = +0.23 and Y2 = 0.0365, which actually produced slightly higher residuals than the earlier calculations. The orbit of Kinoshita (2013) is given below. T ω Ω (2000.0) i q e 1990 Dec. 13.7473 (TT) 182.0131 303.7595 5.0154 2.810968 0.249689

absolute magnitude: H10 = 11 (Meyer) full moon: Jan. 30, Feb. 28, Mar. 30, Apr. 28, May 28 sources: C. S. Shoemaker, E. M. Shoemaker, D. H. Levy, and S. M. Larson, IAUC, No. 5183 (1991 Feb. 8); A. Sugie, R. H. McNaught, and B. G. Marsden, IAUC, No. 5184 (1991 Feb. 11); C. S. Shoemaker, E. M. Shoemaker, D. H. Levy, S. M. Larson, A. Sugie, R. H. McNaught, T. Seki, and B. G. Marsden, MPC, Nos. 17687, 17792 (1991 Feb. 28); D. W. E. Green, IAUC, No. 5248 (1991 Apr. 22); C. S. Shoemaker and E. M. Shoemaker, IAUC, No. 5249 (1991 Apr. 24); C. S. Shoemaker, E. M. Shoemaker, T. Seki, and S. Nakano, MPC, Nos. 18167, 18255 (1991 May 28); A. Hale, ICQ, 13 (1991 Jul.), p. 132; S. Nakano, Nakano Note, No. 559 (1991 Dec. 23); E. W. Elst and G. Traversa, MPC, No. 24933 (1995 Apr. 15); B. G. Marsden, CCO, 12th ed. (1997), pp. 76–7; S. Nakano, CCO, 13th ed. (1999), pp. 80–1; K. Kinoshita correspondence with G. W. Kronk (2000, 2003, 2008, 2013); S. Nakano, Nakano Note, No. 834 (2001 Dec. 23); P. Rocher correspondence with G. W. Kronk (2005); S. Nakano, Nakano Note, No. 993 (2003 Nov. 19); B. G. Marsden, CCO, 16th ed. (2005), pp. 130–1; S. Nakano, Nakano Note, No. 1273 (2005 Oct. 27); S. Nakano, Nakano Note, No. 2607 (2014 Jan. 16).

565

cometography: a catalog of comets

118P/1991 C2 Discovered: 1991 February 9.46 (Δ = 1.73 AU, r = 2.55 AU, Elong. = 138
) (Shoemaker– Last seen: 1991 April 19.14 (Δ = 1.99 AU, r = 2.84 AU, Elong. = 141
) Levy 4) Closest to the Earth: 1991 March 2 (1.6766 AU) Calculated path: VIR (Disc), LEO (Apr. 6) 1990 XII=1991f This comet was found in the course of the Palomar Asteroid and Comet Survey by C. S. Shoemaker, E. M. Shoemaker, and D. H. Levy (Palomar Observatory, California, USA) on film exposed on 1991 February 9.46 using the 46-cm Schmidt telescope. They estimated the magnitude as 17 and described the comet as diffuse, with a faint tail extending in about PA 280
. The position was α = 12h 11.9m, δ = +2
140 (2000). Additional images were obtained on February 11.27 and February 11.30. Independent confirmations of the discovery were obtained by R. H. McNaught (Siding Spring Observatory, New South Wales, Australia) and T. Seki (Geisei, Kochi, Japan). McNaught photographed the comet using the 51-cm Uppsala Southern Schmidt telescope on February 12.74 and estimated the magnitude as 17. Seki photographed it on February 12.77, using his 60-cm reflector, and estimated the magnitude as 16.5. During the remainder of February, magnitude estimates were provided on three nights. E. F. Helin, K. J. Lawrence, and P. Rose (Palomar Observatory) photographed the comet on the 14th and 16th. They were using the 46-cm Schmidt telescope and estimated the magnitude as 17.0 on both nights. Seki photographed the comet on the 20th and estimated the magnitude as 17. The comet continued to be followed during the next two months and reached a maximum elongation of 175
on March 16; however, only four magnitude estimates were ever published. The Shoemakers and Levy gave the magnitude as 16.8 on March 9, 17.9 on April 14, and 18.5 on April 17. Seki estimated the magnitude as 17 on March 16. The comet was last detected during April 19.10–19.14, when astronomers at Oak Ridge Observatory (Massachusetts, USA) acquired CCD images using the 155-cm reflector. No physical descriptions were provided. The position on the final image was α = 11h 32.4m, δ = +9
430 (2000). The first parabolic orbit was calculated by D. W. E. Green on 1991 February 13. He took six positions from February 9–13 and determined the perihelion date as 1990 October 8.42. The first elliptical orbit was calculated by B. G. Marsden and was published on February 26. This used seven positions from February 9–25, giving the perihelion date as 1990 July 19.49 and the period as 6.82 years. Over the next three months, calculations by Marsden and S. Nakano revised the orbit to a perihelion date of July 14.20 and a period of 6.51 years. Using positions spanning the entire period of visibility, Nakano calculated an orbit that was published on December 24. This used 26 positions and included full planetary perturbations. The result was a perihelion date

566

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of July 14.46 and a period of 6.51 years. Nakano (1994) revised the perihelion date to July 14.50. Multiple apparition orbits have been calculated by Marsden (1996, 1999, 2001, 2005), Nakano (1997, 1999, 2003, 2007), K. Kinoshita (1999, 2003, 2010), and P. Rocher (1999, 2003, 2004, 2005, 2006). All of these calculations included full planetary perturbations, while only those published from 2003 onward solved for nongravitational effects. The result was a perihelion date of July 14.27–14.29 and a period of 6.51 years. The nongravitational terms were within the following ranges: A1 = 0.22 to +1.46 and A2 = 0.1498 to 0.1360. The orbit of Marsden (2005) is given below. T ω Ω (2000.0) i q e 1990 Jul. 14.2772 (TT) 302.2645 152.0973 8.4721 2.019494 0.420914

absolute magnitude: H10 = 11.7 (Kronk) full moon: Jan. 30, Feb. 28, Mar. 30, Apr. 28 sources: C. S. Shoemaker, E. M. Shoemaker, and D. H. Levy, IAUC, No. 5185 (1991 Feb. 11); R. H. McNaught, T. Seki, and D. W. E. Green, IAUC, No. 5187 (1991 Feb. 13); E. F. Helin, K. J. Lawrence, P. Rose, and B. G. Marsden, IAUC, No. 5198 (1991 Feb. 26); C. S. Shoemaker, E. M. Shoemaker, D. H. Levy, R. H. McNaught, T. Seki, and B. G. Marsden, MPC, Nos. 17687, 17791 (1991 Feb. 28); C. S. Shoemaker, E. M. Shoemaker, D. H. Levy, R. H. McNaught, T. Seki, E. F. Helin, K. J. Lawrence, and P. Rose, MPC, No. 17687 (1991 Feb. 28); E. F. Helin, K. J. Lawrence, P. Rose, and B. G. Marsden, MPC, Nos. 17856, 17939 (1991 Mar. 30); C. S. Shoemaker, E. M. Shoemaker, D. H. Levy, T. Seki, and S. Nakano, MPC, Nos. 18013, 18081 (1991 Apr. 28); T. Seki, C. S. Shoemaker, E. M. Shoemaker, D. H. Levy, [Oak Ridge], and B. G. Marsden, MPC, Nos. 18167, 18255 (1991 May 28); C. S. Shoemaker, E. M. Shoemaker, and D. H. Levy, MPC, No. 18325 (1991 Jun. 27); S. Nakano, Nakano Note, No. 560 (1991 Dec. 24); C. S. Shoemaker, E. M. Shoemaker, and D. H. Levy, MPC, No. 22713 (1993 Nov. 29); S. Nakano, Nakano Note, No. 602 (1994 Apr. 21); B. G. Marsden, CCO, 11th ed. (1996), pp. 72–3; S. Nakano, CCO, 12th ed. (1997), pp. 74–5; B. G. Marsden, CCO, 13th ed. (1999), pp. 78–9; K. Kinoshita correspondence with G. W. Kronk (1999, 2003, 2010); P. Rocher correspondence with G. W. Kronk (1999, 2003, 2004, 2005, 2006); S. Nakano, Nakano Note, No. 712 (1999 Nov. 3); B. G. Marsden, CCO, 14th ed. (2001), pp. 94–5; S. Nakano, Nakano Note, No. 994 (2003 Nov. 19); S. Nakano, Nakano Note, No. 1452 (2007 Apr. 10). C/1991 C3 Prediscovery: 1991 January 26.72 (Δ = 4.29 AU, r = 4.84 AU, Elong. = 119
) (McNaught– Discovered: 1991 February 12.66 (Δ = 4.09 AU, r = 4.87 AU, Elong. = 137
) Russell) Last seen: 1992 April 30.12 (Δ = 6.12 AU, r = 6.41 AU, Elong. = 102
) Closest to the Earth: 1991 March 9 (3.9789 AU) 1990 XIX=1991g Calculated path: HYA (Pre), CRT (Jan. 31), HYA–CRT (Mar. 1), HYA (Mar. 6), SEX (Mar. 31), LEO (Aug. 2), LMi (1992 Feb. 16) 567

cometography: a catalog of comets

R. H. McNaught (Siding Spring Observatory, New South Wales, Australia) discovered this comet on a photographic plate exposed during 1991 February 12.66–12.70 by his colleague, K. S. Russell. The 122-cm Schmidt telescope was used for this exposure, as part of the Anglo-Australian Near Earth Asteroid Survey. The comet had trailed during the exposure and the magnitude was estimated as 16.5. In addition, McNaught said the coma was moderately condensed and exhibited a tail extending 10 in PA 185
. The position was α = 11h 12.1m, δ = 23
100 (2000). Confirmation came from A. C. Gilmore and P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) and McNaught. Gilmore and Kilmartin photographed the comet on February 13.59 and February 13.67 and estimated the nuclear magnitude as 17.5. McNaught photographed the comet on February 13.62 using the 51-cm Uppsala Southern Schmidt telescope. A prediscovery image was found by McNaught on a photographic plate exposed on January 26.72 by P. McKenzie using the 122-cm Schmidt telescope. He described the image as diffuse and trailed. The position was α = 11h 26.2m, δ = 25
460 (2000). McNaught photographed the comet with the 51-cm Uppsala Southern Schmidt telescope on February 15 and described it as well condensed. On the 19th and 20th, T. Seki (Geisei, Kochi, Japan) photographed the comet using his 60-cm reflector and estimated the magnitude as 17.5. Also on the 20th, E. F. Helin, K. J. Lawrence, and P. Rose (Palomar Observatory, California, USA) photographed the comet using the 46-cm Schmidt telescope and estimated the magnitude as 16.5. Only a few physical descriptions were reported during March. Gilmore and Kilmartin photographed the comet on the 11th and gave the nuclear magnitude as 17.6. On the 14th, Seki estimated the photographic magnitude as 18. A photograph by McNaught on the 20th revealed a magnitude of 16.5. The comet reached a maximum elongation of 157
on the 13th. The comet continued to be followed by several observatories during April and May; however the only physical description obtained during this period came on April 9, when Helin, Lawrence, and Rose estimated the magnitude as 16.5 on film exposed using the 46-cm Schmidt telescope. The last observation of the year came from McNaught on May 16 while using the 51-cm Uppsala Southern Schmidt telescope. The comet’s elongation was then 100
. The comet’s elongation decreased during the next few months, reaching a minimum of 0.3
on September 4. It then began increasing and reached a maximum of 162
on 1992 February 23. The comet was last detected during 1992 April 30.08–30.12, when R. E. McCrosky and C.-Y. Shao (Oak Ridge Observatory, Massachusetts, USA) obtained CCD images using the 155-cm reflector. The position on the last image was α = 10h 14.6m, δ = +33
070 (2000). 568

cometography: a catalog of comets

The first orbit was calculated by D. W. E. Green and was published on 1991 February 15. It was parabolic and used eight positions from January 26 to February 15. The perihelion date was determined as 1990 October 14.43. A parabolic orbit by S. Nakano was published on March 30. This used 17 positions from 1991 January 26 to March 14 and included full planetary perturbations. The result was a perihelion date of October 18.30. The first orbit to use positions spanning the entire period of visibility was calculated by B. G. Marsden (1992). He used 35 positions and included perturbations by Mercury to Pluto. The result was a hyperbolic orbit with a perihelion date of October 18.20 and an eccentricity of 1.00177. This orbit is given below. T ω Ω (2000.0) i q e 1990 Oct. 18.1990 (TT) 320.8865 161.7096 113.4304 4.777087 1.001769

absolute magnitude: H10 = 7 (Meyer) full moon: Dec. 31, 1991 Jan. 30, Feb. 28, Mar. 30, Apr. 28, May 28, Jun. 27, Jul. 26, Aug. 25, Sep. 23, Oct. 23, Nov. 21, Dec. 21, 1992 Jan. 19, Feb. 18, Mar. 18, Apr. 17, May 16 sources: R. H. McNaught and K. S. Russell, IAUC, No. 5187 (1991 Feb. 13); P. McKenzie, A. C. Gilmore, P. M. Kilmartin, R. H. McNaught, and D. W. E. Green, IAUC, No. 5189 (1991 Feb. 15); R. H. McNaught, P. McKenzie, A. C. Gilmore, P. M. Kilmartin, and D. W. E. Green, MPC, Nos. 17688, 17791 (1991 Feb. 28); T. Seki, E. F. Helin, K. J. Lawrence, P. Rose, and S. Nakano, MPC, Nos. 17857, 17940 (1991 Mar. 30); A. C. Gilmore, P. M. Kilmartin, and R. H. McNaught, MPC, No. 18013 (1991 Apr. 28); E. F. Helin, K. J. Lawrence, P. Rose, [Siding Spring], and [Oak Ridge], MPC, No. 18167 (1991 May 28); [Oak Ridge] and R. H. McNaught, MPC, Nos. 18325–6 (1991 Jun. 27); R. E. McCrosky, C.-Y. Shao, and B. G. Marsden, MPC, Nos. 20192, 20308 (1992 Jun. 15); [Siding Spring], MPC, No. 22987 (1994 Feb. 26). 98P/1991 D1 Precovered: 1991 February 12.84 (Δ = 1.81 AU, r = 2.38 AU, Elong. = 114
) (Takamizawa) Recovered: 1991 February 17.49 (Δ = 1.73 AU, r = 2.36 AU, Elong. = 117
) Last seen: 1992 October 18.33 (Δ = 2.84 AU, r = 3.78 AU, Elong. = 158
) 1991 XIII=1991h Closest to the Earth: 1991 May 20 (0.9312 AU) Calculated path: VIR (Pre), BOO (Apr. 27), VIR (May 31), LIB (Jul. 28), SCO (Aug. 30), OPH (Sep. 7), SGR (Oct. 5), CAP (Nov. 23), AQR (1992 Jan. 6), CET (Mar. 5), PSC (Mar. 7), CET (Mar. 22), PSC (May 6), CET (May 29) S. Nakano (1987, 1988, 1989) calculated a new orbit for the 1984 discovery apparition, using 105 positions and full planetary perturbations. He then integrated the motion of the comet to this apparition, predicting the perihelion date as 1991 August 18.43. 569

cometography: a catalog of comets

This comet was recovered by J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) during 1991 February 17.49–17.53 and February 19.45–19.48, when he acquired CCD images using the 91-cm reflector. He gave the magnitude as 19.6–19.9 and detected the presence of a 3000 tail between PA 285
and 290
. The position of the comet on the first image was α = 14h 10.0m, δ = 0
470 (2000). T. Seki (Geisei Observatory, Geisei, Japan) later found a precovery image on a photograph he had exposed on February 12.84 using his 60-cm reflector. The comet was also found on an image he had exposed on February 22.85. Seki estimated the magnitude as 20 on both of these dates. Five observatories reported 45 astrometric positions during March 17 to September 13, with Oak Ridge Observatory (Massachusetts, USA) being responsible for 31 positions. Despite all of these observations, few physical descriptions were reported. Astronomers at Palomar Observatory (California, USA) gave the magnitude as 16.5 on April 8, while Scotti gave the magnitude as 16.9 on April 22. Scotti noted a coma 6000 across and a fan-shaped tail extending 2.00 in PA 252
. Astronomers at Oak Ridge Observatory described the comet as “weak and diffuse” on September 12. The comet reached a maximum elongation of 161
on April 18 and attained its most northerly declination of +8
on May 15. The first visual observation was made on August 4, when C. S. Morris (California, USA) saw the comet using his 51-cm reflector. He gave the magnitude as 14.0 and reported a rather weakly condensed coma 0.740 across. Further visual observations were reported by V. L. Korneev (Zelenograd, Russia) on August 11 and 12. Using a 25-cm reflector, he estimated the magnitude as 12.4 on the first date and gave it as 13.7 on the second. On both of these nights, the comet was moderately condensed, with a coma diameter of 1.50 and 1.20 , respectively. This observer reported further observations on September 25 and 26, estimating the magnitudes as 12.7 and 12.9, respectively. Morris and A. Hale (New Mexico, USA) attempted to observe the comet using larger instruments than Korneev from August 6 through October without success, which certainly brings the late-September observations into question. The final astrometric position was obtained on September 13.01, when R. E. McCrosky and C.-Y. Shao (Oak Ridge Observatory) acquired two CCD images using the 155-cm reflector. The comet’s image was described as “weak” and the position on the last image was α = 16h 38.1m, δ = 19
050 (2000). The comet attained its most southerly declination of 24
on 1991 October 30. The comet was lost in twilight as 1992 began, passing just 6
from the Sun on March 26. The only observations made during the year came from astronomers at El Leoncito (Argentina) when they obtained two CCD images with the 215-cm reflector during October 18.30–18.33. These were also the final observations of this apparition. The comet’s predicted position on the final image was α = 2h 59.2m, δ = +3
480 (2000). J. Licandro, 570

cometography: a catalog of comets

G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton (2000) analyzed these images as part of a program to study cometary nuclei. They said the comet presented “a trailed star-like appearance, but the seeing was not good enough (2.3 arcsec) to assure that there is not a faint coma.” The V magnitude was given as 20.0–20.6. Finally, they estimated that the nucleus has a radius of 3.5 kilometers and noted that this comet was “dynamically old.” Multiple apparition orbits have been calculated by B. G. Marsden (1991, 1992), K. Muraoka (1991), S. Nakano (1995, 2003, 2010, 2013), P. Rocher (1998, 2006, 2013), and K. Kinoshita (1999, 2006, 2013). All of these calculations included full planetary perturbations, while those published from 1998 onward also solved for nongravitational effects. The general result was a perihelion date of 1991 August 17.91 and a period of 7.22 years. The nongravitational terms were within the following ranges: A1 = +0.48 to +0.86 and A2 = +0.0236 to +0.0492. The orbit of Kinoshita (2006) is given below. T ω Ω (2000.0) i q e 1991 Aug. 17.9127 (TT) 147.6774 124.9194 9.4794 1.589776 0.574589

absolute magnitude: H0 = 7.7, n = 12 (Meyer) full moon: Jan. 30, Feb. 28, Mar. 30, Apr. 28, May 28, Jun. 27, Jul. 26, Aug. 25, Sep. 23 sources: S. Nakano, Nakano Note, No. 506 (1987 Aug. 20); S. Nakano, MPC, No. 13045 (1988 May 1); S. Nakano, BAA Handbook for 1990 (1989), p. 77; J. V. Scotti, T. Seki, and B. G. Marsden, MPC, Nos. 17857, 17940 (1991 Mar. 30); [Palomar] and J. V. Scotti MPC, Nos. 18167–8 (1991 May 28); K. Muraoka, Nakano Note, No. 557 (1991 Sep. 4); A. Hale, V. L. Korneev, and C. S. Morris, ICQ, 13 (1991 Oct.), p. 167; R. E. McCrosky and C.-Y. Shao, MPC, Nos. 18852, 18854 (1991 Oct. 23); B. G. Marsden, MPC, No. 20774 (1992 Sep. 12); S. Nakano, Nakano Note, No. 628 (1995 Apr. 22); P. Rocher correspondence with G. W. Kronk (1998, 2006, 2013); K. Kinoshita correspondence with G. W. Kronk (1999, 2006, 2013); J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton, Icarus, 147 (2000 Sep.), pp. 164–5, 175; S. Nakano, Nakano Note, No. 931 (2003 Apr. 14); S. Nakano, Nakano Note, No. 1922 (2010 Apr. 25); S. Nakano, Nakano Note, No. 2469 (2013 Apr. 5). 99P/1991 D2 Precovered: 1991 February 20.72 (Δ = 3.93 AU, r = 4.89 AU, Elong. = 165
) (Kowal 1) Recovered: 1991 February 21.41 (Δ = 3.93 AU, r = 4.89 AU, Elong. = 166
) Last seen: 1995 June 21.44 (Δ = 5.37 AU, r = 6.12 AU, Elong. = 134
) 1992 VI=1991i Closest to the Earth: 1992 April 17 (3.6702 AU) Calculated path: Leo (Pre), VIR (Aug. 9), LIB (1992 Sep. 28), SCO (Dec. 20), OPH (1993 Jan. 29), SCO (Mar. 8), OPH (Oct. 21), SGR (Dec. 12), CAP (1995 Jan. 20) 571

cometography: a catalog of comets

A prediction for the return of this comet was calculated by S. Nakano (1987, 1989) using seven positions from the 1977 apparition, as well as perturbations by Mercury to Pluto. He predicted the comet would next arrive at perihelion on 1992 June 12.88, but noted that the determined period of 15.12 years had a likely error of 7.66 days. J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) recovered this comet on three CCD images obtained using the 91-cm reflector during 1991 February 21.41–21.45. He gave the magnitude as 18.4 and the nuclear magnitude as 21.1. Scotti said the coma was 1500 across, while a tail extended 2900 in PA 297
. The position on the first image was α = 11h 13.6m, δ = +9
140 (2000). Scotti obtained four more CCD images during February 22.30–22.42. He gave the magnitude as 18.4 and the nuclear magnitude as 20.7. Scotti said a tail extended 4000 in PA 295
. The comet was about 3
from the predicted position. A precovery image was subsequently found on a photograph secured at Siding Spring Observatory (New South Wales, Australia) by R. H. McNaught and S. D. Ryder. The photographic plate had been exposed on February 20.72 and the magnitude of the comet was estimated as 18. The comet reached a maximum elongation of 176
on March 5. Thereafter, only two more observations were made during the remainder of 1991 and both were by T. Seki (Geisei Observatory, Geisei, Japan). Seki obtained photographs of the comet on both March 20 and April 3 using his 60-cm reflector. He estimated the magnitude as 18.5 on the first date and 18 on the second. The comet attained its most northerly declination of +11
on April 20. During the next few months, the comet’s elongation decreased until it passed about 1
from the Sun on September 29. The comet was slowly climbing into the morning sky as 1992 began. Seki was the first person to locate the comet when his photographs on February 26 and 27 revealed a magnitude of 17.5. After having moved southward since last April, the comet attained a declination of 11
on February 27 and then began a northward motion. S. M. Larson (Kitt Peak National Observatory, Arizona, USA) acquired six CCD images of the comet with the 229-cm reflector on March 5. He said the tail extended >4000 in PA 299
. Scotti acquired two more images on March 7. He gave the magnitude as 17.3 and said the tail extended 1.430 in PA 298
. The comet reached a maximum elongation of 180
on April 16. Astronomers at La Silla Observatory (Chile) photographed the comet with the 100-cm Schmidt telescope on both April 23 and April 25. The magnitude was estimated as 18.0 on both nights. Scotti also acquired images on April 25 and noted the magnitude as 17.1. Even though the comet was still well placed for observations for a few more months, none were made. After having moved southward since late February, the comet attained a declination of 9
on June 6. The comet reached a minimum elongation of 1
on November 11. No observations were made in 1993 or 1994, despite favorable oppositions on 1993 May 30 (elongation 176
) and 1994 July 6 (175
). The comet 572

cometography: a catalog of comets

was at its minimum elongation on 1993 December 19 (3
). During 1993 the comet moved southward until it attained a declination of 26
on May 5, and then headed northward to 25
by August 7. The comet was heading southward as 1994 began, but after reaching a declination of 27
on January 9, it began a northward motion. This motion continued until March 29, at which time the comet attained a declination of 26
, and then the comet moved southward. The comet attained its most southerly declination of 28
on 1994 August 4. The comet was lost in the Sun’s glare as 1995 began, passing just 4
from the Sun on January 19. After having moved northward since last August, the comet attained a declination of 20
on May 17 and then began a southward motion. The next observations were also the last of this apparition. Scotti obtained four CCD images during 1995 June 21.42–21.44 as the comet was approaching aphelion. The images were obtained using the 91-cm reflector. Scotti gave the magnitude as 20.5–20.7 and the nuclear magnitude as 22.0. The position on the final image was α = 21h 18.7m, δ = 20
510 (2000). The first multiple apparition orbit was calculated by B. G. Marsden and was published on 1991 February 23. It used 15 positions from 1977–1991, as well as perturbations by all nine planets. The perihelion date was given as 1992 March 10.35 and the period was 15.02 years. Additional multiple apparition orbits have been calculated by Nakano (1991, 1996, 2004), Marsden (1992, 2005), P. Rocher (1995, 2006, 2010), and K. Kinoshita (1998, 2005). All of these calculations included full planetary perturbations, while only Kinoshita (2005) solved for nongravitational effects. In addition, Rocher (2010) solved for the relativity effect of the Sun. The result was a perihelion date of March 13.90–13.96 and a period of 15.02 years. Kinoshita (2005) determined the nongravitational terms as A1 = 0.02 and A2 = 0.0063. The orbit of Rocher (2010) is given below. T ω Ω (2000.0) i q e 1992 Mar. 13.9014 (TT) 174.7856 28.7735 4.3919 4.672263 0.232474

absolute magnitude: H0 = 4.5, n = 6 (Meyer) full moon: Jan. 30, Feb. 28, Mar. 30, Apr. 28, May 28, Jun. 27, Jul. 26, Aug. 25, Sep. 23, Oct. 23, Nov. 21, Dec. 21, 1992 Jan. 19, Feb. 18, Mar. 18, Apr. 17, May 16, Jun. 15, Jul. 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6, Mar. 8, Apr. 6, May 6, Jun. 4, Jul. 3, Aug. 2, Sep. 1, Sep. 30, Oct. 30, Nov. 29, Dec. 28, 1994 Jan. 27, Feb. 26, Mar. 27, Apr. 25, May 25, Jun. 23, Jul. 22, Aug. 21, Sep. 19, Oct. 19, Nov. 18, Dec. 18, 1995 Jan. 16, Feb. 15, Mar. 17, Apr. 15, May 14, Jun. 13, Jul. 12 sources: S. Nakano, Nakano Note, No. 499 (1987 Aug. 20); S. Nakano, MPC, No. 14593 (1989 May 20); J. V. Scotti and B. G. Marsden, IAUC, No. 5195 (1991 Feb. 23); J. V. Scotti, R. H. McNaught, S. D. Ryder, and B. G. Marsden, MPC, Nos. 17857, 17940 (1991 Mar. 30); T. Seki, MPC, 573

cometography: a catalog of comets

No. 18013 (1991 Apr. 28); T. Seki, MPC, No. 18167 (1991 May 28); S. Nakano, Nakano Note, No. 556 (1991 Sep. 4); T. Seki, MPC, No. 19728 (1992 Mar. 18); S. M. Larson and J. V. Scotti, MPC, Nos. 19913, 19917 (1992 Apr. 17); [La Silla], MPC, Nos. 20192–3 (1992 Jun. 15); B. G. Marsden, MPC, No. 20775 (1992 Sep. 12); J. V. Scotti, MPC, No. 20862 (1992 Oct. 11); P. Rocher correspondence with G. W. Kronk (1995, 2006, 2010); J. V. Scotti, MPC, No. 25355 (1995 Jul. 12); S. Nakano, Nakano Note, No. 704 (1996 Oct. 31); K. Kinoshita correspondence with G. W. Kronk (1998, 2005); S. Nakano, Nakano Note, No. 1042 (2004 Apr. 4); B. G. Marsden, CCO, 16th ed. (2005), pp. 124–5. 100P/1991 E1 Recovered: 1991 March 12.49 (Δ = 1.05 AU, r = 1.90 AU, Elong. = 137
) (Hartley 1) Last seen: 1991 June 14.10 (Δ = 1.13 AU, r = 1.83 AU, Elong. = 117
) Closest to the Earth: 1991 April 23 (0.8457 AU) 1991 VII=1991j Calculated path: BOO (Rec), VIR (Apr. 10) S. Nakano (1987, 1988, 1990) calculated a new orbit for this comet’s 1985 discovery apparition using 11 positions and perturbations by all nine planets. He the integrated the comet’s motion to this apparition and determined the perihelion date as 1991 April 28.75. In the course of the Palomar Asteroid and Comet Survey (PACS), C. S. Shoemaker, E. M. Shoemaker, and D. H. Levy (Palomar Observatory, California, USA) accidentally recovered this comet on 1991 March 12.49 and March 12.52, when they found it on films exposed using the 46-cm Schmidt telescope. The position on the first image was α = 14h 18.6m, δ = +12
320 (2000). They estimated the magnitude as 16.5 and described the comet as diffuse, with some condensation. A tail extended >10 in PA 285
. The comet was located about 16
from the prediction. The first confirmation of the recovery came from B. Dintinjana and H. Mikuz (Ljubljana, Slovenia) when they acquired three images during March 15.98–16.05 while using a 25-cm telescope. They estimated the magnitude as 17 and noted the coma diameter as 1500 . Only a few observations were obtained during the remainder of March. A. C. Gilmore and P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) photographed the comet on the 16th using a 61-cm reflector, but no descriptive information was provided. R. H. McNaught (Siding Spring Observatory, New South Wales, Australia) also photographed the comet on the 16th using the 51-cm Uppsala Southern Schmidt telescope. He provided no physical description. On the 18th, A. Sugie (Dynic Astronomical Observatory, Shiga, Japan) photographed the comet using a 25-cm Schmidt telescope. He estimated the magnitude as 17.5. T. Seki (Geisei Observatory, Geisei, Japan) photographed the comet on the 20th, using his 60-cm reflector, and estimated the magnitude as 17. The comet was at its brightest in April and May. It was also well placed for observations, as it reached an elongation of 164
on April 17. Only two 574

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observatories provided magnitude estimates. At Kitami (Hokkaido, Japan), A. Takahashi photographed the comet using a 25-cm reflector and estimated the magnitude as 15. The Shoemakers and Levy photographed the comet again on April 14, 16, and 20, giving the magnitude as 16.1 on the first night. Three observers managed to make visual observations of the comet. A. R. Pearce (Dowerin, Western Australia, Australia) was using his 41-cm reflector on April 16. He judged the magnitude as 13.9 and described the coma as slightly condensed and 0.50 across. A. Hale (Las Cruces, New Mexico, USA) saw the comet with his 41-cm reflector on April 18 and 22, giving the magnitude as 14.1 and 13.9, respectively. Hale noted that the comet was “very faint and quite diffuse” and “pretty much a threshold object” on the first night, but appeared “slightly brighter” on the second night. C. S. Morris (California, USA) observed the comet with his 51-cm reflector on May 12. He determined the magnitude as 13.9 and reported a slightly condensed coma 1.10 across. The comet was last detected during June 9.07–9.09 and June 14.09–14.10, when R. E. McCrosky and C.-Y. Shao (Oak Ridge Observatory, Massachusetts, USA) acquired CCD images using the 155-cm reflector. No physical descriptions were provided. The position on the last image was α = 13h 01.5m, δ = 15
380 (2000). B. G. Marsden was the first person to calculate an orbit using two apparitions, the results of which were published on 1991 March 16. This used 15 positions from the 1985 and 1991 apparition, as well as perturbations by all nine planets. The result was a perihelion date of 1991 May 17.68 and a period of 6.02 years. Marsden published a revision on April 28, which used 23 positions. There was little change in the orbital elements. Additional multiple apparition orbits have been calculated by K. Muraoka (1991), Marsden (1994), Nakano (1997, 2000, 2003, 2006, 2013), K. Kinoshita (1998, 2003, 2010, 2013), and P. Rocher (2003, 2004, 2010). All of these calculations included full planetary perturbations, while only those published from 2003 onward solved for nongravitational effects. Rocher (2010) also included the relativity effects of the Sun. The result was a perihelion date of May 17.67–17.68 and a period of 6.02 years. The nongravitational terms were within the following ranges: A1 = +0.18 to +0.26 and A2 = 0.0034 to 0.0014. The orbit of Nakano (2013) is given below. T ω Ω (2000.0) i q e 1991 May 17.6755 (TT) 178.7561 38.9490 25.7246 1.818371 0.450691

absolute magnitude: H10 = 11.5, from visual observations (Meyer) full moon: Feb. 28, Mar. 30, Apr. 28, May 28, Jun. 27 sources: S. Nakano, Nakano Note, No. 505 (1987 Aug. 20); S. Nakano, MPC, No. 13045 (1988 May 1); S. Nakano, BAA Handbook for 1991 (1990 Aug.), p. 78; C. S. Shoemaker, E. M. Shoemaker, D. H. Levy, B. Dintinjana, H. Mikuz, R. H. McNaught, and B. G. Marsden, IAUC, No. 5209 575

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(1991 Mar. 16); A. R. Pearce and A. Hale, IAUC, No. 5246 (1991 Apr. 22); C. S. Shoemaker, E. M. Shoemaker, D. H. Levy, B. Dintinjana, H. Mikuz, R. H. McNaught, A. C. Gilmore P. M. Kilmartin, A. Sugie, T. Seki, and B. G. Marsden, MPC, Nos. 18013, 18015, 18081 (1991 Apr. 28); A. Takahashi, MPC, No. 18165 (1991 May 28); C. S. Shoemaker, E. M. Shoemaker, and D. H. Levy, MPC, No. 18326 (1991 Jun. 27); A. R. Pearce and A. Hale, ICQ, 13 (1991 Jul.), pp. 95–6, 130; R. E. McCrosky and C.-Y. Shao, MPC, No. 18494 (1991 Aug. 25); K. Muraoka, Nakano Note, No. 557 (1991 Sep. 4); R. E. McCrosky and C.-Y. Shao, MPC, No. 18667 (1991 Sep. 23); C. S. Morris, ICQ, 13 (1991 Oct.), p. 165; B. G. Marsden, CCO, 9th ed. (1994), pp. 36, 71; S. Nakano, CCO, 12th ed. (1997), pp. 72–3; K. Kinoshita correspondence with G. W. Kronk (1998, 2003, 2010, 2013); S. Nakano, Nakano Note, No. 713 (2000 May 12); P. Rocher correspondence with G. W. Kronk (2003, 2004, 2010); S. Nakano, Nakano Note, No. 921 (2003 Mar. 17); S. Nakano, Nakano Note, No. 1328 (2006 Apr. 14); S. Nakano, Nakano Note, No. 2506 (2013 Jun. 12). 124P/1991 F1 Prediscovery: 1991 March 15.60 (Δ = 0.43 AU, r = 1.41 AU, Elong. = 162
) (Mrkos) Discovered: 1991 March 16.96 (Δ = 0.43 AU, r = 1.41 AU, Elong. = 164
) Last seen: 1991 July 10.42 (Δ = 1.37 AU, r = 1.83 AU, Elong. = 99
) 1991 IV=1991k Closest to the Earth: 1991 March 23 (0.4195 AU) Calculated path: VIR (Disc), CRV (Mar. 24), CRT (Apr. 3), HYA (Apr. 7), CEN (Apr. 26), ANT (Apr. 26), VEL (May 13), CEN (May 25) A. Mrkos (Klet Observatory, Czech Republic) discovered this rapidly moving object on a photographic plate exposed on 1991 March 16.96. He estimated the magnitude of the trail as 15 and gave the position as α = 12h 47.1m, δ = 3
040 (2000). A confirmation was obtained by Mrkos on March 17.04. He reported the discovery to the Central Bureau for Astronomical Telegrams (Cambridge, Massachusetts, USA) on March 17, but said nothing about the object’s physical appearance. E. F. Helin, K. J. Lawrence, and P. Rose (Palomar Observatory, California, USA) photographed the object on March 18.24, using the 46-cm Schmidt telescope. Helin noted that the object was magnitude 14.0 and “somewhat diffuse.” Mrkos supplied additional positions for March 17.98 and March 18.03. He noted the magnitude as 15 on the latter date and said the object was diffuse, with a central condensation. R. H. McNaught (Siding Spring Observatory, New South Wales, Australia) estimated the magnitude as 15 on March 18.54 and G. Lowe (Perth Observatory, Bickley, Western Australia, Australia) estimated it as 13 on March 18.62. Prediscovery observations of the comet were found. The first was located by Y. Kushida and O. Muramatsu (Yatsugatake South Base Observatory, Hokuto, Yamanashi, Japan) on a photograph exposed on March 16.74. They estimated the magnitude as 14. K. Endate (Kitami, Hokkaido, Japan) found the trailed image of this comet on 15-minute exposures obtained using his 576

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20-cm reflector on March 15.60 and March 15.62. He estimated the nuclear magnitude as 15.5 on the first date. A. C. Gilmore and P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) photographed the comet on March 19. They determined the nuclear magnitude as 15.1 but reported “no obvious coma” on a 30-minute exposure. On March 20, McNaught photographed the comet using the 51-cm Uppsala Southern Schmidt telescope and gave the nuclear magnitude as 14.8. He described the comet as “extremely condensed with [a] very small coma.” On the same night, T. Seki (Geisei, Kochi, Japan) photographed the comet using his 60-cm reflector and gave the magnitude as 13.5. The first visual observation was obtained by A. Hale (Las Cruces, New Mexico, USA) on March 21 using his 41-cm reflector. He gave the magnitude as 13.8 and reported, “the comet appears like a faint star with some diffuseness.” Also on the 21st, Gilmore and Kilmartin gave the nuclear magnitude as 15.6. The comet reached a maximum elongation of 170
on March 23, at which time Seki estimated the magnitude as 13.5. Seki obtained photographs of the comet on April 3 and 8, estimating the magnitude as 14 and 16, respectively. On the 16th, Gilmore and Kilmartin gave the nuclear magnitude as 16.2. C. S. Morris (Lockwood Valley, California, USA) and A. R. Pearce (Dowerin, Western Australia, Australia) visually observed the comet in April. Morris used his 51-cm reflector on the 14th and gave the magnitude as 14.1. Pearce saw the comet with his 41-cm reflector on the 16th and 17th, giving the magnitude as 14.2 and 14.1, respectively. Seki photographed the comet on May 5 and estimated the magnitude as 17. McNaught photographed the comet on May 16 and simply noted the comet was faint. The last observations of this comet were obtained by Gilmore and Kilmartin during June 11.42–11.43 and July 10.40–10.42, when they obtained photographs using a 61-cm reflector. The nuclear magnitude was given as 18.4 on the first date and 19.5 on the last. The last photograph was a 41-minute exposure which revealed a position of α = 12h 28.6m, δ = 48
150 (2000). The first orbit was calculated by D. W. E. Green on 1991 March 19. Using eight positions from March 16–18, he determined a parabolic orbit with a perihelion date of 1991 March 20.99. Green added, “The comet may be of short period.” The first elliptical orbit was calculated by Green and was published on March 22. Using 20 positions from March 16–21, Green determined the perihelion date as March 19.34 and the period as 5.82 years. During the remainder of 1991, S. Nakano calculated improved orbits as further positions were reported. The orbit published on December 24 was the first to use positions spanning the entire apparition. It gave the perihelion date as March 18.97 and the period as 5.64 years. Multiple apparition orbits have been calculated by Marsden (1996, 2005), K. Kinoshita (1998, 2001, 2003, 2008), and Nakano (1999, 2005). These calculations included full planetary perturbations. The result was a 577

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perihelion date of March 18.97 and a period of 5.64 years. The orbit of Kinoshita (2008) is given below. T ω Ω (2000.0) i q e 1991 Mar. 18.9685 (TT) 180.4091 1.6876 31.4872 1.410451 0.554768

absolute magnitude: H10 = 14, from visual observations (Meyer) full moon: Feb. 28, Mar. 30, Apr. 28, May 28, Jun. 27, Jul. 26 sources: A. Mrkos, E. F. Helin, K. J. Lawrence, P. Rose, R. H. McNaught, G. Lowe, and D. W. E. Green, IAUC, No. 5212 (1991 Mar. 19); Y. Kushida, O. Muramatsu, A. C. Gilmore, P. M. Kilmartin, R. H. McNaught, and D. W. Green, IAUC, No. 5220 (1991 Mar. 22); A. Hale, IAUC, No. 5221 (1991 Mar. 22); C. S. Morris and A. Pearce, IAUC, No. 5248 (1991 Apr. 22); K. Endate, Y. Kushida, O. Muramatsu, A. Mrkos, E. F. Helin, K. J. Lawrence, P. Rose, R. H. McNaught, G. Lowe, A. C. Gilmore, P. M. Kilmartin, T. Seki, and S. Nakano, MPC, Nos. 18013–14, 18081 (1991 Apr. 28); T. Seki and S. Nakano, MPC, Nos. 18168, 18256 (1991 May 28); R. H. McNaught, MPC, No. 18326 (1991 Jun. 27); A. C. Gilmore and P. M. Kilmartin, MPC, No. 18494 (1991 Aug. 25); A. C. Gilmore and P. M. Kilmartin, MPC, No. 19068 (1991 Nov. 21); S. Nakano, Nakano Note, No. 561 (1991 Dec. 24); B. G. Marsden, CCO, 11th ed. (1996), pp. 72–3; K. Kinoshita correspondence with G. W. Kronk (1998, 2001, 2003, 2008); S. Nakano, Nakano Note, No. 696 (1999 Oct. 31); B. G. Marsden, CCO, 16th ed. (2005), pp. 128–9; S. Nakano, Nakano Note, No. 1196 (2005 Jul. 4). C/1991 F2 Prediscovery: 1991 February 23.65 (Δ = 3.57 AU, r = 4.25 AU, Elong. = 128
) (Helin– Discovered: 1991 March 17.40 (Δ = 3.14 AU, r = 4.05 AU, Elong. = 152
) Lawrence) Last seen: 1992 October 29.80 (Δ = 2.98 AU, r = 3.81 AU, Elong. = 142
) Closest to the Earth: 1992 January 12 (1.7212 AU) 1992 I=1991l Calculated path: BOO (Pre), VIR (Mar. 16), LEO (Jun. 15), CRT (Aug. 13), CRV (Sep. 22), HYA (Oct. 16), CEN (Nov. 3), MUS (Dec. 16), CIR (Dec. 21), APS (Dec. 22), OCT (1992 Jan. 4), TUC (Jan. 19), PHE (Feb. 3), SCL (Feb. 24), CET (Mar. 19), PSC (Jul. 24), ARI (Jul. 27), PSC (Aug. 14), PEG (Oct. 5) In the course of the Palomar Planet-Crossing Asteroid Survey, E. F. Helin and K. J. Lawrence (Palomar Observatory, California, USA) found this comet on film exposed with the 46-cm Schmidt telescope during 1991 March 17.40–17.42. They described the comet’s appearance as “extremely dense, with a tail fanning to the north-north-east” and about magnitude 15. The position on the first image was α = 13h 34.7m, δ = +8
370 (2000). A prediscovery image was found by M. Ishikawa (Fukaya, Saitama, Japan). It was located on a photograph exposed with a 30-cm comet-patrol camera during February 23.65–23.75. The magnitude was estimated as 15. The position was α = 13h 55.4m, δ = +7
550 (2000). 578

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Confirming observations were made by A. C. Gilmore and P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) during March 19.60–19.62 using a 61-cm reflector, R. H. McNaught (Siding Spring Observatory, New South Wales, Australia) on March 19.69 using the 51-cm Uppsala Southern Schmidt telescope, and G. Lowe (Perth Observatory, Bickley, Western Australia, Australia) on March 19.72 using the 33-cm astrograph. Gilmore and Kilmartin determined the nuclear magnitude as 15.4. McNaught estimated the magnitude as 15 and noted the comet was strongly condensed. Only a few physical descriptions were published during the remainder of March. T. Seki (Geisei, Kochi, Japan) and McNaught photographed the comet on the 20th. Seki estimated the magnitude as 15, while McNaught’s short exposure using the 51-cm Uppsala Southern Schmidt telescope revealed a magnitude of 14.5, a strongly condensed coma, and a tail extending 10 in PA 350
. Gilmore and Kilmartin determined the nuclear magnitude as 15.5 on the 21st. Seki estimated the magnitude as 14.5 on the 23rd. The first and only visual observation in March was made by A. Hale (Las Cruces, New Mexico, USA) on the 21st. He was using his 41-cm reflector and judged the magnitude as 13.6. Four visual observers managed to follow the comet in April, before moonlight began to interfere. J. E. Bortle (Stormville, New York, USA) saw the comet on the 4th, using his 50-cm reflector. He determined the magnitude as 12.9 and noted a moderately condensed coma 0.50 across. Also on the 4th, the comet reached a maximum elongation of 165
. Hale saw the comet on the 5th, but noted, “observation hampered by a faint star [that] the comet passed over.” Nevertheless, he judged the magnitude as 13.6. R. J. Bouma (Groningen, Netherlands) observed the comet with his 25-cm reflector on the 8th and 11th, giving the magnitude as 13.5 and 13.4, respectively. He reported a slightly condensed coma 0.40 across. Hale determined the magnitude as 13.4 on the 14th. On the 16th, A. R. Pearce (Dowerin, Western Australia, Australia) saw the comet with his 41-cm reflector and gave the magnitude as 13.9. He noted a slightly condensed coma 0.60 across. The comet had been moving in a westerly direction following its discovery, drifting slowly toward the north. After attaining a declination of +9
on April 10, it maintained the predominantly westerly motion, but began drifting toward the south. Six visual observers saw the comet in May, with only two seeing the comet on more than one night. All observers noted only slight condensation within the coma. W. C. Morrison (Canada) observed the comet on the 4th with his 45-cm reflector. He judged the magnitude as 13.6 and said the coma was 0.60 across. R. J. Modic (Ohio, USA) and Hale saw the comet on the 11th. Modic was using his 40-cm reflector, noting a magnitude of 14.0 and a coma 0.450 across. Hale determined the magnitude as 13.5. The magnitude was determined as 13.6 by Pearce on both the 12th and 16th. He noted the coma diameter as 0.7’ on the first night. On the 15th, Bouma 579

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gave the magnitude as 13.1 and said the coma was 1.10 across. G. Comello (Netherlands) observed the comet using his 28-cm reflector on the 17th. He determined the magnitude as 12.9 and said the coma was 0.50 across. Hale saw the comet on May 19, giving the magnitude as 13.6. The number of visual observations greatly diminished in June and July, with most observers noting very little condensation. Morris used his 51-cm reflector on June 2 and 8, noting magnitudes of 13.7 and 13.8, respectively. He gave the coma diameter as 0.60 on the first night and 1.00 on the second night. Hale saw the comet on June 4 and 17, giving the magnitudes as 13.0 and 13.3, respectively. Modic determined the magnitude as 14.8 on June 13 and 14.4 on the 14th. The coma diameter was 0.25–0.300 . V. L. Korneev (Zelenograd, Russia) observed the comet using his 25-cm reflector on July 1. He gave the magnitude as 12.8 and the coma diameter as 20 . Hale determined the magnitude as 13.5 on July 4. He remarked, “altitude fairly low, background sky somewhat bright; the comet was very vague.” Helin and Lawrence photographed the comet on July 9 and 11 using the 46-cm Schmidt telescope, and determined the magnitude as 16.0. For the next few months, the comet was lost in the Sun’s glare, reaching a minimum elongation of 17
on September 24. The comet was next observed on November 18, when McNaught photographed it and estimated the magnitude as 12. He noted that the comet was strongly condensed. A visual observation was made by A. F. A. L. Jones (Nelson, New Zealand) on December 9. He was using his 32-cm reflector and determined the magnitude as 12.0. He added that the coma was very slightly condensed and 0.50 across. Two photographs were obtained by Gilmore on December 10. He used a 61-cm reflector and Kodak SB Panoramic Dental Film to obtain exposures of 10 and 5 minutes. Kilmartin (2015) said that Gilmore estimated the nuclear magnitude as 14.5 and added that he visually spotted the comet through that telescope before taking the pictures. Curiously, two anomalously bright visual estimates were made on December 13.69 and December 14.70 by J. Seach (New South Wales, Australia), giving the magnitude as 8.9 and 8.8, respectively. He was using 15  80 binoculars and gave the diameter as 20 on both nights. Although the comet could have experienced a significant brightness outburst at the time, there are no other reports from these dates. The next observation of the comet was made by McNaught and D. I. Steel at Siding Spring Observatory. They used the 102-cm reflector and a V filter to acquire four CCD images of this comet on December 20. Each exposure was 60 seconds long. McNaught wrote, “with my observing notes, I have printouts of the comet images and although the seeing was very poor, it would surprise me if the comet was anything like mag 9. A diffuse outer coma could account for it though.” The comet had been moving southward since last April and attained its most southerly declination of 84
on 1992 January 7. Two days later, the comet reached a maximum elongation of 62
. The final visual observation 580

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was reported by G. J. Garradd (New South Wales). On January 13, he used a 25-cm reflector to estimate the magnitude as 13.3. Garradd described the comet as only weakly condensed and 1.00 in diameter. Two observatories continued to follow the comet during the first three months of 1992. A short exposure by McNaught on January 3, revealed a nuclear magnitude of 15. McNaught said the comet appeared “very condensed” with “no hint of coma.” Three more images were acquired by McNaught on January 15, but no physical descriptions were provided. Gilmore photographed the comet on February 5, March 3, and March 8, giving the nuclear magnitude as 16.3 and 16.7 on the last two nights. The comet reached a minimum elongation of 23
on April 18. As it moved away from the Sun, it was also continuing to move northward and again became accessible to observers in the Northern Hemisphere. From late June to early September, visual observations were attempted by Modic, Hale, A. Nakamura (Kuma Kogen Astronomical Observatory, Ehime, Japan), and S. Garro (France), using telescopes ranging from 20-cm to 60-cm, but without success. The only observations reported during this period were made at Mauna Kea (Hawaii, USA) and Oak Ridge Observatory (Massachusetts, USA). K. J. Meech and T. L. Farnham (Mauna Kea) used the 224-cm reflector and an R filter to acquire CCD images on August 2 and 3. No physical descriptions were given. R. E. McCrosky and C.–Y. Shao (Oak Ridge Observatory) used the 155-cm reflector to acquire CCD images on July 29 and August 3, 24, and 31. The final astrometric positions were measured on CCD images obtained during September 25.22–25.23 and September 30.22–30.23 by McCrosky and Shao. They were using the 155-cm reflector. No descriptive information was provided. The position on the last image was α = 0h 25.3m, δ = +16
260 (2000). The comet also attained its most northerly declination of +16.5
on September 30 and reached a maximum elongation of 167
on October 2. The final observation was obtained on October 29.80, when W. Hasubick (Germany) photographed the comet using a 140-mm lens. He estimated the magnitude as 15.0 and said the coma was less than 10 across. P. Pravec (Ondřejov Observatory, Czech Republic) tried to acquire a CCD image of the comet on November 29 using an 18-cm reflector, but was unsuccessful. He concluded that the comet was fainter than about magnitude 15. The first orbit was calculated by D. W. E. Green and was published on 1991 March 21. It was a parabolic orbit, based on 10 positions from March 17–21, and gave the perihelion date as 1992 February 19.17. Revised parabolic orbits were published by B. G. Marsden on April 28 and S. Nakano on May 28, providing perihelion dates of January 20.25 and January 20.03, respectively. Marsden published the first hyperbolic orbit on June 27. This used 51 positions from 1991 February 23 to June 2 and included perturbations by all nine planets. The result was a perihelion date of 1992 January 20.01 and an eccentricity of 1.00058. Marsden published revised orbits on 581

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1992 February 18 and August 13 as additional positions were reported. On the final date, he determined the perihelion date as January 20.03 and the eccentricity as 1.00044. Nakano (1993) published the only orbit that used positions spanning 1991 February 23 to 1992 September 30. He used 97 positions and full planetary perturbations. The result was a perihelion date of January 20.03 and an eccentricity of 1.00043. This orbit is given below. The 8th edition of Marsden’s Catalogue of Cometary Orbits included original and future orbits for this comet. The original orbit was elliptical with a period of about 16 million years, while the future orbit is hyperbolic with an eccentricity of 1.00017. T ω Ω (2000.0) i q e 1992 Jan. 20.0270 (TT) 271.1592 11.8349 95.4565 1.517721 1.000431

absolute magnitude: H10 = 5.5, from visual observations (Meyer) full moon: Jan. 30, Feb. 28, Mar. 30, Apr. 28, May 28, Jun. 27, Jul. 26, Aug. 25, Sep. 23, Oct. 23, Nov. 21, Dec. 21, 1992 Jan. 19, Feb. 18, Mar. 18, Apr. 17, May 16, Jun. 15, Jul. 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10 sources: E. F. Helin, K. J. Lawrence, and R. H. McNaught, IAUC, No. 5213 (1991 Mar. 19); A. C. Gilmore, P. M. Kilmartin, G. Lowe, R. H. McNaught, and D. W. E. Green, IAUC, No. 5215 (1991 Mar. 21); A. Hale, IAUC, No. 5219 (1991 Mar. 21); R. H. McNaught, IAUC, No. 5221 (1991 Mar. 22); J. E. Bortle, A. Hale, and A. R. Pearce, IAUC, No. 5247 (1991 Apr. 22); E. F. Helin, K. J. Lawrence, A. C. Gilmore, P. M. Kilmartin, R. H. McNaught, G. Lowe, T. Seki, and B. G. Marsden, MPC, Nos. 18014–15, 18082 (1991 Apr. 28); M. Ishikawa and S. Nakano, MPC, Nos. 18168, 18256 (1991 May 28); B. G. Marsden, MPC, No. 18395 (1991 Jun. 27); A. Hale, J. E. Bortle, and A. R. Pearce, ICQ, 13 (1991 Jul.), pp. 95, 128; E. F. Helin and K. J. Lawrence, MPC, No. 18494 (1991 Aug. 25); G. Comello, C. S. Morris, V. L. Korneev, and A. Hale, ICQ, 13 (1991 Oct.), pp. 149, 164; A. F. A. L. Jones, ICQ, 14 (1992 Jan.), p. 20; R. H. McNaught and D. I. Steel, MPC, Nos. 19361, 19370 (1992 Jan. 19); R. H. McNaught and B. G. Marsden, MPC, Nos. 19561, 19654 (1992 Feb. 18); A. F. A. L. Jones and G. J. Garradd, IAUC, No. 5455 (1992 Feb. 21); A. C. Gilmore, MPC, No. 19728 (1992 Mar. 18); R. J. Modic and A. R. Pearce, ICQ, 14 (1992 Apr.), p. 38; A. C. Gilmore, MPC, No. 19913 (1992 Apr. 17); G. J. Garradd and A. Hale, ICQ, 14 (1992 Jul.), p. 73; R. E. McCrosky, C.–Y. Shao, and B. G. Marsden, MPC, Nos. 20544, 20602 (1992 Aug. 13); R. E. McCrosky and C.-Y. Shao, MPC, No. 20672 (1992 Sep. 12); J. Seach and A. Hale, ICQ, 14 (1992 Oct.), p. 108; R. E. McCrosky and C.-Y. Shao, MPC, No. 20962 (1992 Nov. 10); B. G. Marsden, CCO, 8th ed. (1993), p. 98; W. C. Morrison, R. J. Modic, and A. Nakamura, ICQ, 15 (1993 Jan.), pp. 20–1; S. Nakano, Nakano Note, No. 576 (1993 Jan. 9); S. Garro and P. Pravec, ICQ, 15 (1993 Apr,), p. 72; T. L. Farnham, K. J. Meech correspondence with G. W. Kronk (1994); R. J. Bouma, ICQ, 16 (1994 Apr.), p. 43; 582

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W. Hasubick, ICQ, 17 (1995 Jul.), p. 141; D. I. Steel, R. H. McNaught correspondence with G. W. Kronk (2015); P. M. Kilmartin correspondence with G. W. Kronk (2015); A. C. Gilmore correspondence with G. W. Kronk (2015). X/1991 G1 Three people independently found this apparent comet in 2005 September. R. Haver (Frasso Sabino, Italy) and R. J. Bouma (Groningen, Netherlands) detected the trail in mid-September on a 60-minute exposure originally taken during 1991 April 11.60–11.62, in the course of the Second Epoch Southern Sky Survey with the 122-cm Schmidt telescope at Siding Spring Observatory (New South Wales, Australia). Both were searching for precovery images of comet 213P/van Ness, which was predicted close to the position of the unknown object but should have had a different orientation of movement. Bouma, who reported the trail on 2005 September 17, measured a nuclear magnitude of 19.5 and described it as a “faint trail surrounded by considerable nebulosity, particularly on the western side.” He also noted a “faint tail, maybe 10 long towards roughly PA 245
.” M. Meyer (Kelkheim, Germany) found the trail on September 27, also during a search for precovery images of comet 213P. He estimated the magnitude as 18 and said it appeared as a “diffuse trail with condensation.” He said that the object “shows a tail at least 3000 in length in PA 245260
.” The positions of the ends of the diffuse trail are α = 13h 59m 25.01s, δ = 27
320 24.000 (2000) and α = 13h 59m 26.55s, δ = 27
320 09.100 (2000). Since there is only one image, the direction of motion is unknown, so the positions might need to be switched. sources: R. J. Bouma report to Minor Planet Center (2005 Sep. 17); M. Meyer report to Minor Planet Center (2005 Sep. 27); R. Haver correspondence to M. Meyer (2005 Oct. 1); R. J. Bouma correspondence to M. Meyer (2015 Aug. 30). 21P/Giacobini– Recovered: 1991 February 16.52 (Δ = 3.90 AU, r = 4.06 AU, Elong. = 92
) Zinner Last seen: 1991 July 4.32 (Δ = 2.68 AU, r = 3.20 AU, Elong. = 111
) Closest to the Earth: 1992 April 7 (2.0166 AU) 1992 IX=1991m Calculated path: LIB (Rec), SER (Feb. 20), BOO (May 28) A prediction for the return of this comet was published by D. K. Yeomans (1989). He took 1145 positions from 1972–1987, included full planetary perturbations, and solved for nongravitational effects. He then integrated the comet’s motion to this apparition and predicted a perihelion date of 1992 April 13.23. This was a very unfavorable return. The comet was recovered by K. J. Meech (Mauna Kea, Hawaii, USA) during 1991 February 16.52–16.61. She was using the 224-cm reflector and an R filter, obtaining 31 CCD images with a total integration time of 583

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5580 seconds. She noted, “No apparent coma” and estimated the nuclear magnitude as 22. The position was α = 15h 47.7m, δ = 3
580 (2000) on February 16.53. Meech asked W. G. Weller (Cerro Tololo Inter-American Observatory, Chile) to confirm her recovery, so he acquired CCD images of the comet’s predicted position on March 14.39 and March 15.36, using the 61-cm CurtisSchmidt telescope. Both images revealed a stellar object moving at the rate expected for this comet. The precise positions not only confirmed that Yeomans’ prediction required a correction of just 0.01 day, but they were the final positions measured for this apparition, with the comet at α = 15h 54.1m, δ = 1
080 (2000) on the last image. The next observation of this comet was obtained by Meech (Cerro Tololo) on May 12, using the 402-cm reflector and an R filter. She obtained 20 CCD images, for a total integration of 3000 seconds. She wrote, “Hint of coma.” The comet reached a maximum elongation of 155
on May 7 and attained its most northerly declination of +11
on June 24. The comet was last detected during July 4.29–4.32, when Meech (Mauna Kea) acquired 10 CCD images using the 224-cm reflector and an R filter. The total integration time was 1350 seconds. No physical description was provided. Multiple apparition orbits have been calculated by S. Nakano (1995, 2002, 2005, 2009), P. Rocher (2000), B. G. Marsden (2003), and K. Kinoshita (2003, 2008). All of these calculations included full planetary perturbations and solved for nongravitational effects. The general result was a perihelion date of April 13.21–13.24 and a period of 6.61 years. The most consistent set of nongravitational terms came from Nakano (1995, 2005, 2009) and Kinoshita (2008), which were within the following ranges: A1 = +0.24 to +0.42 and A2 = 0.0740 to 0.0597. Marsden determined the following terms A1 = 0.10 and A2 = 0.0751. Rocher (2000) and Nakano (2002) only used two apparitions, which spanned 1991–1999. Rocher (2000) gave the terms as A1 = +0.11 and A2 = 0.1791, while Nakano (2002) gave the terms as A1 = 0.13 and A2 = 0.0389. The orbit of Nakano (2009) is given below. T ω Ω (2000.0) i q e 1992 Apr. 13.2286 (TT) 172.5169 195.3837 31.8221 1.034027 0.706486

absolute magnitude: H10 = 12.5 (Meyer) full moon: Jan. 30, Feb. 28, Mar. 30 sources: D. K. Yeomans, MPC, No. 14592 (1989 May 20); K. J. Meech and W. G. Weller, IAUC, No. 5225 (1991 Mar. 28); K. J. Meech and W. G. Weller, MPC, No. 18015 (1991 Apr. 28); K. J. Meech correspondence with G. W. Kronk (1994); S. Nakano, Nakano Note, No. 629 (1995 Apr. 22); P. Rocher correspondence with G. W. Kronk (2000); B. G. Marsden, CCO, 15th ed. (2003), pp. 82–3; S. Nakano, Nakano Note, No. 847 (2002 May 7); K. Kinoshita 584

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correspondence with G. W. Kronk (2003, 2008); S. Nakano, Nakano Note, No. 1177 (2005 May 4); S. Nakano, Nakano Note, No. 1761 (2009 Apr. 20). 4P/Faye Recovered: 1991 April 16.80 (Δ = 2.99 AU, r = 2.56 AU, Elong. = 56
) Last seen: 1993 May 27.23 (Δ = 4.07 AU, r = 4.41 AU, Elong. = 103
) 1991 XXI=1991n Closest to the Earth: 1991 October 28 (0.6161 AU) Calculated path: AQR (Rec), PSC (May 18), CET (Nov. 12), TAU (1992 Jan. 24), ORI (Mar. 4), TAU (Apr. 3), ORI (Apr. 6), GEM (Apr. 22), CNC (Jun. 8), LEO (Jul. 28), SEX (Aug. 25), LEO (Oct. 1), VIR (Nov. 14), LEO (1993 Mar. 13) A prediction for the return of this comet was published by B. G. Marsden (1988). He took 82 positions from 1961–1985, included perturbations by all nine planets, and solved for nongravitational effects. Marsden then integrated the comet’s motion to this apparition and predicted a perihelion date of 1991 November 16.19. This comet was recovered by T. Seki (Geisei, Kochi, Japan) on 1991 April 16.80 and April 19.81, when he photographed the predicted position using his 60-cm reflector. He gave the magnitude as 18.5 and 18.0, respectively, and noted a small coma. The position on the first image was α = 22h 02.0m, δ = 4
220 (2000). The comet was next detected on June 4, when Seki obtained a photograph that revealed a magnitude of about 17. Both A. Hale (Las Cruces, New Mexico, USA) and R. J. Modic (Ohio, USA) attempted to visually see the comet in June and July, but were unsuccessful. Hale used his 41-cm reflector on June 18 and suggested the comet was probably fainter than magnitude 13.5. Modic observed with his 40-cm reflector on June 20 and July 15 and suggested the comet must have been fainter than magnitude 14.0 and 14.5, respectively. Visual observations were finally made in August. Modic spotted the comet on the 7th, giving the magnitude as 14.1. He said the coma was strongly condensed and 900 across. Modic saw the comet on five more nights from the 8th to the 19th. He reported magnitudes of 12.9–13.1 and consistently noted a moderately condensed coma 0.7–1.00 across. V. L. Korneev (Zelenograd, Russia) was the most prolific observer during the month, seeing the comet on seven nights from the 8th to the 14th with his 25-cm reflector. He estimated magnitudes of 13.3–13.6 and reported a slightly condensed coma 1.5–2.00 across. Korneev also reported seeing a tail on August 12–14. He said it extended 3600 in PA 100–105
. C. S. Morris (Lockwood Valley, California, USA) saw the comet through a break in the clouds with his 51-cm reflector on the 11th, estimating the magnitude as 12.5. He said the coma was slightly condensed and 4400 across. Hale saw the comet on both the 12th and 20th, judging the magnitude as 12.7 and 12.5, respectively. On the former night, he reported a small coma that was “condensed and fan-shaped.” R. J. Bouma (Groningen, Netherlands) observed the 585

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comet with his 25-cm reflector on the 21st. He determined the magnitude as 12.4 and said the coma was slightly condensed and 5400 across. W. Hasubick (Germany) photographed the comet on the 7th using a 140-mm lens. He estimated the magnitude as 12.5 and noted a moderately condensed coma 10
; the band had a uniform width of about 20 .” It should be noted that Earth intersected the comet’s orbital plane on October 13. The comet slowly faded in November but was still followed closely by visual observers. C. S. Spratt (Victoria, British Columbia, Canada) saw the comet on five nights between the 6th and 29th, using a 20-cm reflector and noted the magnitude decreased from 8.9 to 9.7. Bouma observed the comet on five nights between the 4th and 14th, reporting magnitudes of 9.3–9.5. M. Meyer (Frauenstein, Germany) applied a 13-cm reflector and 25  100 binoculars on four nights between the 1st and 30th, noting a brightness decrease from magnitude 9.9 to 10.5. All observers generally noted a moderately condensed coma that was 2–50 across in the first half of the month and 2–30 across in the second half. A number of observations of the tail were also reported, indicating that the maximum length decreased from 0.5
to less than 0.1
as the month progressed. As the comet faded in December, the number of reported observations continued to decrease. After having moved southward since late August, the comet attained a declination of +1
on December 5 and then began a northward motion. Möller saw the comet on 11 nights between the 4th and 30th, noting a brightness decrease from magnitude 10.6 to 11.6. Modic observed the comet on five nights between the 11th and 28th, using mainly a 20-cm reflector and documented a brightness decrease from magnitude 10.0 to 11.7. Korneev saw the comet on six nights between the 2nd and 31st, reporting that the magnitude faded from 9.4 to 10.2. During the month, the coma generally remained slightly to moderately condensed, with a diameter of 1–30 . In early December some observers still saw a tail with a length of up to 11’ while at the end of the month it was less than 10 . S. Garro (France) saw the comet on the 4th using his 20-cm reflector. He said the tail extended 80 in PA 40
, while a jet extended 1800 from the nucleus toward PA 80
. On December 30, Bortle noted that a Swan-band filter “just about extinguishes” the comet. The comet continued fading in 1992 January and the number of visual observers noticeably decreased. Bouma saw the comet on five nights between the 4th and 26th, reporting a brightness decrease from 10.9 to 11.7. Möller observed the comet on three nights between the 4th and 10th, and generally noticed a decrease from magnitude 11.5 to 11.7. Korneev saw the comet on January 25, 30, and 31, and estimated magnitudes of 11.2, 11.4 and 11.5, respectively. Most observers reported a slightly condensed coma, 587

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the diameter of which was estimated as 0.60 to 3.50 during the month. Garro reported seeing the tail on the 1st while using his 20-cm reflector. He noted that it extended 20 in PA 70
. J. Armstrong (Georgia, USA) saw the tail with his 41-cm reflector on the 8th, noting that it extended 30 in PA 40
. Less than 20 observations were reported to the ICQ in February, as some observers reported the comet was too faint for their smaller telescopes. Modic saw the comet on the 3rd, 4th, and 6th, and reported the magnitude as 12.8 on all three occasions. Bouma observed the comet on the 3rd, 23rd, and 29th, and gave magnitudes of 12.1, 12.8, and 13.0, respectively. Korneev found the comet on the 11th, 12th, and 14th, estimating the magnitude as 12.1 on the first two nights and 12.3 on the last. Descriptions of the coma generally indicated it as slightly condensed, with a diameter that varied from about 0.50 to 1.50 during the month. Modic was the only visual observer in March. Using his 36-cm reflector on the 1st, he gave a magnitude of 13.2, noting a slightly condensed coma 3600 across. He observed the comet with his 40-cm reflector on the 28th and 29th, giving the magnitude as 13.6 and reporting a slightly condensed coma 2400 across. The comet was photographed on the 22nd and 30th by T. Kojima (Chiyoda, Gunma, Japan) using a 25-cm reflector. He estimated the magnitude as 14 on the first night and 14.5 on the last night. No further observations were reported for the next few months, as the comet dropped into twilight. Modic did attempt to see the comet with his 40-cm reflector on April 6 but was unsuccessful, suggesting it must have been fainter than magnitude 14.0. The comet attained its most northerly declination of +15.4
on 1992 April 30. The comet reached a minimum elongation of 5
on August 22. The only other observation reported in 1992, was made by Scotti on December 2, when CCD images acquired with the 91-cm reflector revealed a magnitude of 20.120.8. Scotti was the only observer in 1993. On January 23, he reported a magnitude of 20.4–20.7 and a nuclear magnitude of 22.4. In addition, he said the coma was 1100 across, while a tail extended 6.80 in PA 286
. Scotti’s images on March 3 revealed a magnitude of 20.5. He then noted a coma 1000 in diameter and a tail extending 9.050 in PA 286
. On March 30, Scotti judged the magnitude as 20.4 and the nuclear magnitude as 22.4. The coma was 1200 across and the tail extended 19.90 in PA 286
. The comet had attained its most southerly declination of 6
on January 15. It then reached a maximum elongation of 175
on March 15. The final observation for this apparition was made by Scotti during May 27.2027.23. He determined the nuclear magnitude as 21.7–22.0 and noted a faint, narrow tail extending 2.10 in PA 282
. The position on the final image was α = 11h 13.5m, δ = +1
410 (2000). P. L. Lamy and I. Toth (1995) observed the comet on seven dates between 1991 October 29 and November 21, using the Planetary Camera of the Hubble Space telescope. Assuming an albedo of 0.04, they determined the 588

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radius of the nucleus as 2.342.91 km. They said the shape was “rather spherical”. Multiple apparition orbits have been calculated by Marsden (1997), Nakano (1996, 2003, 2006), K. Kinoshita (1999, 2003, 2006, 2008), and P. Rocher (2000, 2006, 2009). These calculations included full planetary perturbations and solved for nongravitational effects. Rocher (2009) included the relativity effects of the Sun. The result was a perihelion date of November 16.18–16.19 and a period of 7.34 years. For the orbits published during 1996–2003, the nongravitational terms were within the following ranges: A1 = +0.44 to +0.64 and A2 = 0.0146 to 0.0049. For the orbits published during 2006–2011, the nongravitational terms were within the following ranges: A1 = +0.49 to +0.63 and A2 = 0.0352 to 0.0272. The orbit of Rocher (2009) is given below. T ω Ω (2000.0) i q e 1991 Nov. 16.1848 (TT) 203.9381 199.5950 9.0858 1.593430 0.578162

absolute magnitude: H0 = 6.0, n = 8.2 (Shanklin, 1997) full moon: Mar. 30, Apr. 28, May 28, Jun. 27, Jul. 26, Aug. 25, Sep. 23, Oct. 23, Nov. 21, Dec. 21, 1992 Jan. 19, Feb. 18, Mar. 18, Apr. 17, May 16, Jun. 15, Jul. 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6, Mar. 8, Apr. 6, May 6, Jun. 4 sources: B. G. Marsden, MPC, No. 13042 (1988 May 1); T. Seki, IAUC, No. 5246 (1991 Apr. 22); T. Seki, MPC, No. 18168 (1991 May 28); A. Hale, ICQ, 13 (1991 Jul.), p. 132; C. S. Morris and A. Hale, IAUC, No. 5325 (1991 Aug. 15); T. Seki, MPC, No. 18494 (1991 Aug. 25); R. J. Modic, V. L. Korneev, C. S. Morris, A. Hale, and M. Möller, ICQ, 13 (1991 Oct.), pp. 150, 173–6; D. L. Rabinowitz and J. V. Scotti, IAUC, No. 5366 (1991 Oct. 15); J. E. Bortle, M. Meyer, and M. Möller, ICQ, 14 (1992 Jan.), pp. 67, 246; A. Nakamura, V. L. Korneev, R. J. Modic, C. S. Spratt, and M. Möller, ICQ, 14 (1992 Apr.), pp. 459; T. Kojima, MPC, No. 19914 (1992 Apr. 17); T. Kojima, MPC, No. 20371 (1992 Jul. 14); S. Garro, ICQ, 14 (1992 Oct.), pp. 104, 119–20; R. J. Modic and J. Armstrong, ICQ, 15 (1993 Jan.), pp. 312; J. V. Scotti, MPC, No. 21305 (1993 Feb. 6); J. V. Scotti, MPC, Nos. 21631, 21637 (1993 Mar. 8); R. J. Bouma, ICQ, 16 (1994 Apr.), pp. 66–7; J. V. Scotti, MPC, Nos. 21833, 21837 (1993 Apr. 6); J. V. Scotti, MPC, Nos. 21981, 21989 (1993 May 6); J. V. Scotti, MPC, Nos. 22278, 22286 (1993 Aug. 2); P. L. Lamy and I. Toth, AAP, 293 (1995 Jan.), pp. 435L; G. S. Keitch, ICQ, 17 (1995 Jan.), p. 37; W. Hasubick, ICQ, 17 (1995 Jul.), pp. 145–6; S. Nakano, Nakano Note, No. 637 (1996 Apr. 11); B. G. Marsden, CCO, 12th ed. (1997), pp. 48–9; J. D. Shanklin, JBAA, 107 (1997 Aug.), p. 188; K. Kinoshita correspondence with G. W. Kronk (1999, 2003, 2006, 2008); P. Rocher correspondence with G. W. Kronk (2000, 2006, 2009); S. Nakano, Nakano Note, No. 943 (2003 Apr. 21); S. Nakano, Nakano Note, No. 1368 (2006 Sep. 26); S. Nakano, Nakano Note, No. 2145 (2011 Nov. 1). 589

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101P/1991 L1 Recovered: 1991 June 8.41 (Δ = 2.85 AU, r = 3.00 AU, Elong. = 89
) (Chernykh) Last seen: 1993 April 20.16 (Δ = 4.08 AU, r = 4.21 AU, Elong. = 90
) Closest to the Earth: 1991 September 26 (1.5912 AU) 1992 II=1991o Calculated path: AQR (Rec), CET (Dec. 13), PSC (Dec. 14), CET (1992 Jan. 6), PSC (Feb. 4), CET (Mar. 6), ARI (Mar. 17), TAU (Apr. 15), ORI (Jun. 28), GEM (Jul. 15), CNC (Sep. 14) The recovery of this comet began with the calculations of S. Nakano (1980, 1987). He took over 220 positions from the 1978 apparition and applied full planetary perturbations. He then integrated the comet’s motion to this apparition. The 1980 calculations revealed a perihelion date of 1992 January 27.99, while the 1987 calculations revealed a perihelion date of January 27.82. J. V. Scotti and D. L. Rabinowitz (Steward Observatory, Kitt Peak, Arizona, USA) recovered this comet on three CCD images acquired during 1991 June 8.41–8.44 using the 91-cm reflector. The position on the first image was α = 23h 13.5m, δ = 6
410 (2000), while the nuclear magnitude was given as 20.3 on the last image. Scotti and Rabinowitz also imaged the comet on June 10.46–10.47. The first image revealed a coma 800 across and a fan-shaped tail extending over 800 toward PA 252
. After having moved northward since its recovery, the comet attained a declination of 4
on July 21 and then began a southward motion. Although no observatories followed the comet in July and August, several visual observers began looking for it at the beginning of August. The only definite visual observations during the month came from O. Midtskogen (Tranby, Norway) on the 17th and 31st, when his 32-cm reflector revealed magnitudes of 11.6 and 12.0, respectively. The coma was described as moderately condensed on both occasions, with a diameter of 1.20 on the 17th and 0.80 on the 31st. C. S. Morris (Lockwood Valley, California, USA) tried to see the comet on August 4 and 11 using a 51-cm reflector. He said the comet must have been fainter than magnitude 13.7 and 14.0, respectively. On both dates he saw a probable candidate at magnitude 14.0 and 14.2, respectively, but could not confirm it. A. Hale (Las Cruces, New Mexico, USA) reported unsuccessful attempts of August 6, 13, and 21, using a 41-cm reflector, where he said the comet was fainter than magnitude 13.0, 13.0, and 13.5, respectively. There were several attempts by observers to visually see the comet in September, but few were successful. Midtskogen saw the comet on the 1st and judged the magnitude as 12.2. He noted a slightly condensed coma 0.60 across. G. Comello (Groningen, Netherlands) reported seeing the comet with his 20-cm reflector on the 30th. He estimated the magnitude as 12.8 and said the coma was very slightly condensed and 20.80 . Several observers obtained images of the comet during April. Nakamura gave the magnitude as 15.6 on the 1st, 15.5 on the 14th, and 15.7 on the 17th. He measured the coma diameter as 0.30 , 0.350 , and 0.450 , respectively. Nakamura added that the tail extended toward PA 295
on the 1st and 17th and PA 290
on the 14th. K. Endate (Kitami, Hokkaido, Japan) used a 25-cm hyperboloid astro camera and gave the magnitude as 16 on the 10th, 16th, and 20th. K. Kawanishi (Akou, Hyogo, Japan) used a 20-cm reflector and estimated the magnitude as 15.5 on the 17th. The comet reached a maximum elongation of 173
on April 15. May was the final month of observations for 1993. S. Nakano (Sumoto, Hyogo, Japan) acquired a CCD image on the 14th using a 20-cm reflector. He gave the magnitude as 16.3. Nakamura determined the magnitude as 15.9 on the 15th and 16.1 on the 20th, giving the coma diameter as 0.350 and 0.40 , respectively. He added that the tail extended toward PA 295
on both nights. Nakano determined the magnitude as 15.8–15.9 on the 24th. The comet reached a minimum elongation of 2
on November 17. The only observations reported during 1994 came from H. Debehogne (La Silla Observatory, Chile). Using the 100-cm Schmidt telescope, six precise positions were measured from images acquired during June 9 and 10. The magnitude was estimated as 18 on the 9th. The comet reached a maximum elongation of 179
on June 11. The comet was lost in the Sun’s glare as 1995 began, reaching a minimum elongation of 2
on January 3. The first observations of the year were obtained by Nakamura on May 8, when he determined the magnitude as 18.0 and the coma diameter as 0.30 . On May 23, Nakamura again determined the magnitude as 18.0, but reported a coma 0.40 across. Nakamura 645

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reported a magnitude of about 17.6 on June 1, noting a coma 0.350 across. CCD images were obtained by astronomers as La Silla Observatory on July 2 and 3 while using the 154-cm reflector. J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton (2000) analyzed the La Silla images as part of a program to study cometary nuclei. They said the comet was very active and added that it “was even possible to observe the onset of a tail.” They determined the V magnitude as 18.7–19.0 and the R magnitude as 18.3–18.5. They also estimated the radius of the nucleus as 10.5 kilometers. The comet reached a maximum elongation of 174
on July 26. On July 27, Nakamura determined the magnitude as 17.4 and the coma diameter as 0.350 . He also reported a tail extending 2.10 in PA 266
. On August 16, Nakamura gave the magnitude as 17.6. He added that the coma was 0.30 across, while a tail extended toward PA 250
. A. Fitzsimmons and I. M. Cartwright (La Palma, Canary Islands, Spain) used the 99-cm Jacobus Kapteyn Telescope to acquire four 300-second CCD exposures during August 25–26. They gave the B magnitude as 18.8, the V magnitude as 17.8, and the R magnitude as 17.4. Two R images were combined and revealed “a dust coma extending ~8.3 arcsec.” They determined the upper limit of the nuclear radius as 7.11.1 kilometers. C. W. Hergenrother (Catalina Station, Mt. Bigelow, Arizona, USA) obtained three CCD images using the 154-cm reflector on August 30. He determined the magnitude as 17.2–17.6 and said the coma was moderately condensed and 11” across. Nakamura obtained the final observations of the year, when he acquired three CCD images on October 13. He gave the magnitude as 17.9 and said the coma was 1500 across. The comet was lost in the Sun’s glare as 1996 began, passing 5
from the Sun on February 10. Nakamura obtained the first observations of the year, when two CCD images revealed the magnitude as 18.8 on July 16. He said the coma was 1500 across. On July 24, Nakamura determined the magnitude as 18.7. He reported a coma 1200 across and a tail extending 1.90 in PA 247
. Two more images were obtained by Nakamura on August 18, which revealed a magnitude of about 18.1. He also noted a coma 1800 across and a tail extending 2.40 in PA 253
. The comet reached a maximum elongation of 172
on September 1. Nakamura acquired a CCD image of the comet on September 15 and gave the magnitude as 18.3. He added that the coma was 1500 across. Three CCD images by Nakamura on October 5 revealed a magnitude of 18.2, a coma diameter of 1800 , and a tail extending 2.60 in PA 254
. W. Offutt (Cloudcroft, New Mexico, USA) obtained four CCD images using a 60-cm reflector on October 14, judging the magnitude as 18.8–19.1. The final observations of this apparition came during October 16.53–16.54, when Nakamura acquired two CCD images. He determined the magnitude as 18.1. He also noted a coma 2100 across and a tail extending 2.30 in PA 255
. The position on the last image was α = 22h 36.9m, δ = 17
090 (2000). The comet passed aphelion on October 18. 646

cometography: a catalog of comets

Multiple apparition orbits have been calculated by S. Nakano (1989, 1998, 2003, 2004, 2006, 2007, 2013), B. G. Marsden (1996), and K. Kinoshita (2001, 2003, 2007). All of these calculations included full planetary perturbations, while only those published from 2001 onward solved for nongravitational effects. The result was a perihelion date of August 5.92–5.93 and a period of 8.57 years. The initial attempts at determining the nongravitational terms were made by Kinoshita, producing values of A1 = +13.83 and A2 = 20.6920 in 2001 and A1 = +13.68 and A2 = 21.4719 in 2003. Kinoshita (2007) determined the terms as A1 = +0.01 and A2 = 0.0033. Nakano (2004, 2006, 2007, 2013) calculated nongravitational effects based on S. Yabushita’s theory of sublimating carbon monoxide (or molecular nitrogen). He determined nongravitational terms within the following ranges: Y1 = +0.04 to +0.10 and Y2 = 0.0138 to 0.0107. The orbit of Nakano (2004) is given below. T ω Ω (2000.0) i q e 1992 Aug. 5.9255 (TT) 88.9953 77.4806 6.6294 3.572134 0.147312

absolute magnitude: H0 = 5, n = 6 (Meyer) full moon: Annual Comet: full moons do not limit the overall period of the comet’s visibility sources: S. Nakano, Nakano Note, No. 520 (1987 Dec. 10); [Klet], MPC, No. 15441 (1989 Dec. 12); K. J. Meech and [Cerro Tololo], MPC, No. 16294 (1990 Jun. 8); T. Seki, MPC, No. 17683 (1991 Feb. 28); T. Seki, MPC, No. 19359 (1992 Jan. 19); S. Otomo and S. Ueda, MPC, No. 19727 (1992 Mar. 18); T. Seki, MPC, No. 20071 (1992 May 16); T. Kojima, MPC, No. 20369 (1992 Jul. 14); T. Seki and J. V. Scotti, MPC, Nos. 21629–30, 21637 (1993 Mar. 8); J. V. Scotti, MPC, Nos. 21981, 21989 (1993 May 6); K. Endate, K. Kawanishi, and S. Nakano, MPC, No. 22114 (1993 Jun. 4); A. Nakamura and S. Nakano, MPC, No. 22277 (1993 Aug. 2); A. Nakamura and S. Nakano, ICQ, 15 (1993 Oct.), p. 172; K. J. Meech correspondence with G. W. Kronk (1994); A. Nakamura, MPC, No. 25098 (1995 May 14); A. Nakamura, MPC, Nos. 25249–50 (1995 Jun. 13); A. Nakamura, MPC, No. 25466 (1995 Aug. 10); A. Nakamura, A. Fitzsimmons, and I. M. Cartwright, MPC, No. 25559 (1995 Sep. 9); A. Nakamura and C. W. Hergenrother, ICQ, 17 (1995 Oct.), p. 211; H. Debehogne and A. Nakamura, MPC, No. 25751 (1995 Nov. 7); C. W. Hergenrother, MPC, No. 25996 (1995 Dec. 7); B. G. Marsden, CCO, 11th ed. (1996), pp. 66–7; A. Nakamura, ICQ, 18 (1996 Jan.), p. 33; A. Nakamura, MPC, No. 27483 (1996 Jul. 30); A. Nakamura, MPC, No. 27757 (1996 Sep. 27); A. Nakamura and W. Offutt, MPC, No. 27956 (1996 Oct. 26); A. Nakamura, ICQ, 19 (1997 Jan.), pp. 47–8; C. S. Shoemaker and E. M. Shoemaker, MPC, No. 29341 (1997 Apr. 22); S. Nakano, Nakano Note, No. 666 (1998 Apr. 26); A. Fitzsimmons, I. M. Cartwright, and I. P. Williams, AAP, 349 (1999), 649–59; J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton, Icarus, 147 (2000 647

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Sep.), pp. 164–5, 175; K. Kinoshita correspondence with G. W. Kronk (2001, 2003, 2007); S. Nakano, Nakano Note, No. 1002 (2003 Dec. 6); S. Nakano, Nakano Note, No. 1129 (2004 Dec. 6); S. Nakano, Nakano Note, No. 1320 (2006 Apr. 9); S. Nakano, Nakano Note, No. 1485 (2007 Jul. 9); S. Nakano, Nakano Note, No. 2592 (2013 Dec. 22). 31P/ Recovered: Visible throughout orbit Schwassmann– Last seen: Visible throughout orbit Wachmann 2 Closest to the Earth: 1994 January 25 (1.0858 AU) Calculated path: SGR (Aphelion), CAP (Dec. 14), AQR (1991 Apr. 23), CAP 1994 II (Aug. 7), AQR (1992 Jan. 1), PSC (Apr. 27), CET (Jun. 11), PSC (Sep. 22), AQR (Nov. 15), PSC (Dec. 4), CET (1993 Jan. 23), PSC (Feb. 20), CET (Apr. 12), ARI (Apr. 17), TAU (May 29), ORI (Aug. 15), GEM (Aug. 31), CNC (Oct. 25), LEO (1994 May 10), VIR (Jul. 31), LIB (Nov. 9), SCO (1995 Jan. 20), OPH (Feb. 9), SCO (May 17), LIB (Jun. 14), SCO (Sep. 3), OPH (Oct. 1), SGR (Dec. 15), CAP (1997 Jan. 23) Predictions for the return of this comet were calculated by G. Forti (1989) and S. Nakano (1990, 1991). They used positions from 1973–1989, included full planetary perturbations, and solved for nongravitational effects. After integrating the comet’s motion to this apparition, the perihelion date was determined as 1994 January 23.90 by Forti and January 23.91 by Nakano. The comet passed aphelion on 1990 November 11. The comet attained its most southerly declination of 22
on 1990 November 11 and its most northerly declination of +21
on 1993 August 20. The comet was lost in the Sun’s glare as 1991 began, reaching a minimum elongation of 0.2
on January 30. The first observations of this apparition were made by K. J. Meech (Cerro Tololo Inter-American Observatory, Chile). Using the 402-cm reflector and an R filter, she acquired four CCD images during May 13.37–13.38 and noted a “hint of a tail.” The comet’s predicted position on the first image was α = 20h 18.6m, δ = 18
310 (2000). The comet reached a maximum elongation of 178
on August 18. The first astrometric positions of this apparition were obtained by J. X. Luu and D. C. Jewitt (Kitt Peak National Observatory, Arizona, USA). Using a 240-cm reflector and an R filter, they acquired three CCD images during September 12.32–12.33, 15 images during September 14.14–14.34, and 31 images during September 15.11–15.32. The magnitudes were determined as 20.73–20.93 on the 12th, 20.87–21.31 on the 14th, and 20.66–21.30 on the 15th. The large number of precise magnitude estimates revealed that the nucleus made one rotation in 5.58 hours. Luu and Jewitt determined the upper limit of the nucleus’ radius as 3.1 kilometers. In addition, although no coma was visible in the individual exposures, they noted that when several images were combined, “a faint coma extension toward the west was observed.” The earliest given position was α = 21h 36.2m, δ = 16
030 (2000) on September 12.33. 648

cometography: a catalog of comets

The comet was lost in the Sun’s glare as 1992 began, passing just 2
from the Sun on March 2. Using the 91-cm reflector, J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) obtained three CCD images of the comet on September 24, giving its magnitude as 17.2 and the nuclear magnitude as 20.5. He described the comet as exhibiting a coma 2500 in diameter and displaying a tail 0.580 long in PA 254
. A further observation was made by Scotti on the 25th when he gave the magnitude as 18.0. Observations were also made on the 25th and 30th, when R. E. McCrosky and C.-Y. Shao (Oak Ridge Observatory, Massachusetts, USA) obtained CCD images with the 155-cm reflector; however, no physical descriptions were provided. The comet reached a maximum elongation of 176
on September 27. No further observations were made during the remainder of 1992. Three images of the comet were obtained by Scotti on 1993 January 24, when the magnitude was given as 17.9 and the central condensation was 20.9. The coma was 1200 across, while the tail extended 0.520 in PA 68
. These were the only observations early in the year, as the comet’s elongation was decreasing during the first months of 1993, reaching a minimum of 3
on April 30. After the comet moved out of twilight, four CCD images were obtained by M. Cavagna and C. Gualdoni (Sormano, Italy) while using a 50-cm reflector on August 17. They noted a diffuse coma and a stellar central condensation. The magnitude was determined as 15.9, the coma diameter was 1800 , and the tail extended 1.20 in PA 258
. A. Nakamura (Kuma Kogen Astronomical Observatory, Ehime, Japan) obtained CCD images on August 24 and 27, using the 60-cm reflector. He gave the magnitude as 15.6, the coma diameter as 0.3–0.350 , and noted a tail extending 20 in PA 270
. The first visual observation was reported by B. H. Granslo (Fjellhamar, Norway) on September 18. He was using a 30-cm reflector. Granslo judged the magnitude as 13.1 and noted a slightly condensed coma 0.40 across. During the remainder of September, CCD images were acquired by P. Pravec and M. Wolf (Ondřejov Observatory, Czech Republic) and Nakamura. Pravec and Wolf were using an 18-cm reflector. They determined the CCD magnitude as 15.5, noted a coma 0.40 across, and said the tail extended 3.60 in PA 275
. Nakamura determined the magnitude as 14.9 on the 26th. He also reported a coma diameter of 0.40 and said a tail extended 3.60 in PA 275
. Two observers reported visual observations in October. R. J. Modic (Ohio, USA) saw the comet with a 46-cm reflector on the 14th and determined the magnitude as 14.5. He noted a slightly condensed coma 2100 across. R. J. Bouma (Groningen, Netherlands) saw the comet with his 25-cm reflector on the 17th and judged the magnitude as 13.0. He said the coma was 1.00 across and completely uncondensed. Modic again saw the comet on the 24th, but was using his 36-cm reflector. He gave the magnitude as 14.6 and said the coma was slightly condensed and 2400 across. Nakamura obtained CCD images on the 11th and 22nd, which revealed a 649

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tail. It extended 4.80 toward PA 275
on the first night and 6.60 toward PA 275
on the second night. The comet slowly brightened during November. S. Garro (France) observed it with his 20-cm reflector on the 9th. He determined the magnitude as 13.4 and said the coma was very slightly condensed and 0.40 across. Modic saw the comet on the 9th and 10th, giving the magnitude as 14.0 and 14.2, respectively. He noted a slightly condensed coma 0.50 across. Bouma judged the magnitude as 12.4 on both the 17th and 18th. He indicated that the coma was very slightly condensed and 1.2–1.30 across. On the 19th, G. Comello (Groningen, Netherlands) observed with a 28-cm reflector and described the comet as very slightly condensed and about magnitude 12.5. G. W. Kronk (Troy, Illinois, USA) saw the comet with his 33-cm reflector on the 29th, during a total lunar eclipse. He estimated the magnitude as 12.3 and said the coma appeared slightly condensed and 0.70 across. A tail was detected on CCD images obtained by Nakamura and Pravec. Nakamura said it extended more than 60 toward PA 280
on the 14th. Pravec was using a 65-cm reflector on the 20th and described the tail as “well-developed . . . with a narrow structure at tail axis.” He said it extended more than 7.80 toward PA 282
on the 20th. Pravec also noted a nuclear magnitude of 15.3. The comet brightened even more in December. Kronk followed it on the 7th, 8th, and 9th, noting a magnitude of 12.5–12.6. He reported a slightly condensed coma 0.6–0.80 across. On the 11th, G. Keitch (England) used a 30-cm reflector to determine the comet’s magnitude as 11.4 and its diameter as 1.40 . Kronk gave the magnitude as 12.4 on the 12th and said the coma was 0.60 across. Keitch observed the comet with a pair of 25  150 binoculars on the 14th, judging the magnitude as 11.0 and the coma diameter as 1.30 . On the 15th, A. Hale (Orogrande, New Mexico, USA) saw the comet with his 41-cm reflector and determined the magnitude as 12.6. On the 17th, Bouma gave the comet’s magnitude as 11.9. He said the coma was slightly condensed and 2.0’ across. On the 23rd, Keitch used his 30-cm reflector to gauge the magnitude as 11.2 and the coma diameter as 1.70 , noting that it had become rather strongly condensed. Astronomers at Kiso Observatory (Nagano, Japan) obtained CCD images of the comet on December 14, with the 105-cm Schmidt telescope. They noted a nuclear magnitude of 14.0. A CCD image by Nakamura on the 11th revealed a tail extending over 80 toward PA 285
. H. Mikuz (Ljubljana, Slovenia) used a 20-cm reflector, a CCD camera, and a V filter on the 12th and 17th. He said the tail extended about 7.80 in PA 300
on the first night and about 150 in PA 280
on the second night. The comet passed closest to the Sun and Earth in the second half of 1994 January. It was also well positioned for observations, reaching a maximum elongation of 180
on January 25. Hale gave the magnitude as 12.1 on the 4th while using his 20-cm reflector. Keitch judged the magnitude as 11.1–11.2 on the 4th and 5th. He also noted a moderately condensed coma 1.50 across. Bouma gave the magnitude as 11.7 on the 6th and 9th. 650

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He measured the coma as 1.80 across. Using 25  150 binoculars on the 10th, Keitch determined the magnitude as 11.0 and the coma diameter as 1.50 . With the aid of a 20-cm refractor, M. Lehky (Hradec Králové, Czech Republic) estimated the magnitude at 11.3 on the 15th. On the 16th, Bouma and C. S. Morris (California, USA) independently gave the magnitude as 11.6. Morris was using a 26-cm reflector, and reported a “tiny comet with parabolic coma and tail.” He estimated the coma diameter as 0.80 and said the tail extended 30 in PA 270
. With his 20  100 binoculars, Keitch determined the magnitude as 10.5 and the coma diameter as 30 on the 17th. That same night, Morris determined the magnitude as 11.8 while using his 26-cm reflector. He added that the coma was moderately condensed and 1.00 across. C. E. Spratt (Victoria, British Columbia, Canada) was observing with his 20-cm reflector on the 20th. He gave the magnitude as 11.3 and noted a very slight condensation in a coma 2.00 across. On the 30th, Spratt and Keitch judged the magnitude as 10.6 and 10.8, respectively. The coma diameter was given as 2.00 by Spratt and 1.90 by Keitch. The comet was most observed in February, with observers noting very little change in brightness. J. E. Bortle (Stormville, New York, USA) saw the comet on six nights spanning the 3rd to the 28th, using his 32-cm reflector. He determined magnitudes of 10.1–10.3, while the coma remained moderately condensed and 2.3–2.50 across. On the 3rd, Bortle noted “a minute, but strong knot of bright material occupies coma’s center, possibly containing a very faint, stellar nucleus of mag [approximately equals] 13.5.” On the 7th, Bortle wrote, “essentially-stellar nucleus of mag 13–13.5 at heart of coma, heavily involved with surrounding material.” Keitch saw the comet on six nights from the 4th to the 27th, using 20  100 and 25  150 binoculars. He gave magnitudes of 10.7–10.9, while the coma was moderately condensed and 1.60 to 2.70 across. Comello observed the comet on nine nights from the 2nd to the 19th, using a 20-cm and 28-cm reflector. He determined magnitudes of 10.7–11.2, noting very little condensation in a coma 1–1.50 across. A CCD image was obtained by Nakamura on the 3rd, which revealed a tail extending more than 6.60 in PA 280
. The comet faded in March, with most observers reporting a weakly condensed coma. Bortle determined the magnitude as 10.3 on the 2nd and said the coma was 2.00 across. He next saw the comet on the 12th, judging the magnitude as 10.5 and the coma diameter as 1.70 . Another observation on the 31st revealed a magnitude of 10.7 and a coma diameter of 3.50 . Kronk saw the comet on seven nights spanning the 3rd to the 19th. He indicated that the magnitude generally faded from 11.6 to 12.2, while the coma diameter was 0.7–1.10 . Keitch followed the comet with 25  150 binoculars from the 2nd to the 11th. He said the coma faded from 11.1 to 11.9, while the coma was 1.4–1.60 across. Mikuz acquired two CCD images at the end of the month. On the 29th, he noted a fan-like tail extending about 40 toward PA 95
. On the 30th, he noted a fan-like tail extending about 50 toward about PA 110–130
. 651

cometography: a catalog of comets

The comet continued to fade in April and there was a dramatic drop in reported observations from the previous month. Observers generally reported only a slight condensation. Bouma saw the comet from the 2nd to the 6th, reporting a magnitude of 12.8–12.9 and a coma diameter of 1.0–1.30 . Hale saw the comet on the 6th, reporting a magnitude of 12.2. Morris observed the comet on the 11th. He said the magnitude was 13.2, while the coma was 1.10 across. A CCD image by Nakamura on the 8th revealed a tail extending 30 in PA 115
. A CCD image by Mikuz on the 29th revealed a fan-like tail extending about 20 in PA 110
. Only a few visual observations were reported in May. On the 2nd, the comet was seen by V. Znojil (Czech Republic) and Bouma. Znojil was using 25  100 binoculars. He gave the magnitude as 12.3 and said the coma was moderately condensed and 0.80 across. Bouma judged the magnitude as 13.1 and said the coma was very slightly condensed. Another observation was made by Znojil on the 7th, using a 12-cm reflector. He determined the magnitude as 12.8 and said the coma was moderately condensed and 1.20 across. On the 14th, S. Garro (France) gave the magnitude as 13.4, noting a slightly condensed coma 0.30 across. Cavagna obtained a CCD image on the 1st, which revealed a coma 1.00 across and a tail extending 20 in PA 113
. A CCD image by Mikuz on the 3rd, revealed a fan-like tail that extended about 30 in PA 110
. Nakamura obtained a CCD image on the 6th and said the tail extended 40 in PA 115
. Another image by Mikuz on the 27th revealed a tail extending 30 in PA 135
. The comet reached a maximum elongation of 175
on May 26. Only three observers followed the comet in June. Lehky apparently made the final visual observations, judging the magnitude as 11.8 on the 1st, 12.2 on the 8th, and 12.3 on the 12th. On both the 1st and 8th, he described the comet as an “inconspicuous and very diffuse nebula with weak central condensation.” The coma diameter was estimated as 10 . On the 12th, Lehky described the comet as “perfectly visible at first sight. Small and very diffuse nebula with weak central condensation.” The coma was 0.50 across. A CCD image was acquired by Nakamura on the 1st. He determined the magnitude as 14.3 and the coma diameter as 0.950 . In addition, Nakamura reported a tail extending 2.40 in PA 115
. T. Kojima (Chiyoda, Gunma, Japan) obtained three CCD images using his 25-cm reflector on the 3rd, but no physical descriptions were provided. The final observations of 1994 were made by Nakamura, when he obtained two CCD images on July 5. The magnitude was determined as 14.6, the coma was 0.70 across, and a tail extended toward PA 115
. The comet moved into twilight shortly thereafter and reached a minimum elongation of 3
on October 23. The first observations of 1995 came in April. On the 2nd, S. M. Larson and C. W. Hergenrother (Catalina Station, Mt. Bigelow, Arizona, USA) obtained three CCD images using the 154-cm reflector. They determined the magnitude as 18.8–19.0. Nakamura obtained two CCD images on the 652

cometography: a catalog of comets

7th, giving the magnitude as 18.6. Additional images were acquired by Nakamura on the 23rd, when he judged the magnitude as 18.2 and said the coma was 0.30 across. Nakamura was the sole observer in May, giving the CCD magnitude as 17.9 on the 5th, 17.4 on the 23rd, and 17.7 on the 31st. He said the coma was 0.350 across on the 5th, while a tail extended toward PA 300
. On the 23rd, Nakamura gave the coma diameter as 0.40 and said the tail extended toward PA 260
. He measured the coma diameter as 0.350 on the 31st. Nakamura and Pravec independently obtained CCD images on June 29, with the magnitude determined as 17.8 and 18.4, respectively. Nakamura said the coma was 0.350 across. Pravec said the coma was circular and 0.30 across, exhibiting a rather strong central condensation. He noted a nuclear magnitude of 19.4. The comet was last detected on July 4.22, when Larson obtained two CCD images using the 154-cm reflector. Hergenrother analyzed the images, giving the magnitude as 18.1–18.2 and the coma diameter as 800 . The position on the last image was α = 15h 51.7m, δ = 16
060 (2000). Thereafter, the comet reached a minimum elongation of 2
on December 19, a maximum elongation of 178
on 1996 July 5, a minimum elongation of 0
on 1997 January 18, and a maximum elongation of 179
on 1997 August 4. The comet passed aphelion on 1997 December 21. Multiple apparition orbits have been calculated by S. Nakano (1996, 2001, 2003), P. Rocher (2001, 2002, 2003), and K. Kinoshita (2003, 2004, 2010). These calculations included full planetary perturbations and solved for nongravitational effects. The perihelion date was generally given as January 23.92, while the period was 6.39 years. All of these calculations except Kinoshita (2010) determined nongravitational terms within the following ranges: A1 = +0.97 to +1.37 and A2 = 0.2963 to 0.2721. Kinoshita (2010) was the first to not use positions made prior to 1993. He determined the nongravitational terms as A1 = +0.05 and A2 = 0.0018. Interestingly, orbits published by Rocher (2012) and the Minor Planet Center (2012), which did not include positions made prior to 2000, produced low residuals without the need for nongravitational effects. The orbit of Kinoshita (2010) is given below. T ω Ω (2000.0) i q e 1994 Jan. 23.9173 (TT) 358.2188 126.2464 3.7531 2.070258 0.398751

absolute magnitude: H0 = 6.4, n = 6 (Meyer) full moon: Annual Comet: full moons do not limit the overall period of the comet’s visibility sources: G. Forti, AAP, 215 (1989), pp. 382–3, 385; S. Nakano, Nakano Note, No. 544 (1990 May 20); S. Nakano, MPC, No. 18256 (1991 May 28); J. X. Luu, D. C. Jewitt, J. V. Scotti, R. E. McCrosky, and C.-Y. Shao, MPC, Nos. 20860, 653

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20865 (1992 Oct. 11); J. X. Luu and D. C. Jewitt, AJ, 104 (1992 Dec.), pp. 2243–9; J. V. Scotti, MPC, Nos. 21630, 21637 (1993 Mar. 8); M. Cavagna, C. Gualdoni, and A. Nakamura, MPC, No. 22520 (1993 Sep. 30); M. Cavagna, C. Gualdoni, and B. H. Granslo, ICQ, 15 (1993 Oct.), pp. 144, 166; P. Pravec, M. Wolf, and A. Nakamura, MPC, No. 22610 (1993 Oct. 30); P. Pravec, R. J. Modic, G. W. Kronk, A. Hale, H. Mikuz, and C. E. Spratt, ICQ, 16 (1994 Jan.), pp. 5, 20–1; B. H. Granslo, G. W. Kronk, C. E. Spratt, G. Comello, and J. E. Bortle, IAUC, No. 5941 (1994 Feb. 24); [Kiso], MPC, No. 23152 (1994 Mar. 27); A. Nakamura, S. Garro, G. Comello, M. Lehky, C. S. Morris, J. E. Bortle, G. W. Kronk, and H. Mikuz, ICQ, 16 (1994 Apr.), pp. 34–5, 61–4; R. J. Bouma, A. Hale, H. Mikuz, A. Nakamura, M. Cavagna, V. Znojil, and S. Garro, ICQ, 16 (1994 Jul.), pp. 84, 117–18; A. Nakamura, MPC, No. 23698 (1994 Jul. 22); G. Keitch and A. Nakamura, ICQ, 16 (1994 Oct.), p. 170; M. Lehky, ICQ, 17 (1995 Jan.), p. 33; A. Nakamura, ICQ, 17 (1995 Apr.), p. 77; B. G. Marsden, MPEC, No. 1995-G09 (1995 Apr. 8); T. Kojima, MPC, No. 24935 (1995 Apr. 15); S. M. Larson, C. W. Hergenrother, and A. Nakamura, MPC, No. 25098 (1995 May 14); A. Nakamura, MPC, No. 25248 (1995 Jun. 13); P. Pravec, ICQ, 17 (1995 Jul.), pp. 95, 151; S. M. Larson, C. W. Hergenrother, A. Nakamura, and P. Pravec, MPC, No. 25354 (1995 Jul. 12); C. W. Hergenrother and A. Nakamura, ICQ, 17 (1995 Oct.) p. 207; S. Nakano, Nakano Note, No. 691 (1996 Jun. 30); P. Rocher correspondence with G. W. Kronk (2001, 2002, 2003, 2012); S. Nakano, CCO, 14th ed. (2001), pp. 76–7; K. Kinoshita correspondence with G. W. Kronk (2003, 2004, 2010); S. Nakano, Nakano Note, No. 1006 (2003 Dec. 7); [Minor Planet Center], MPC, No. 79344 (2012 May 6). C/1992 A1 Discovered: 1992 January 9.50 (Δ = 2.57 AU, r = 3.50 AU, Elong. = 157
) (Helin–Alu) Last seen: 1993 March 23.69 (Δ = 3.48 AU, r = 3.92 AU, Elong. = 109
) Closest to the Earth: 1992 February 6 (2.4482 AU) 1992 XVI=1992a Calculated path: HYA (Disc), CMi (Jan. 22), MON (Feb. 20), HYA (May 15), CRT (Sep. 6), HYA (Sep. 8), CEN (Oct. 24), LUP (Dec. 30), NOR (1993 Feb. 5), CIR (Feb. 7), NOR (Feb. 22) In the course of the Palomar Planet-Crossing Asteroid Survey, E. F. Helin and J. T. Alu (Palomar Observatory, California, USA) discovered this comet on film exposed during 1992 January 9.50–9.52 and on January 10.49, using the 46-cm Schmidt telescope. They estimated the magnitude as 16.5 and described the comet as “diffuse without central condensation.” The position on the first image was α = 8h 22.6m, δ = +5
030 (2000). The comet was observed from two observatories during the remainder of January. T. Seki (Geisei, Kochi, Japan) photographed the comet with his 60-cm reflector on the 23rd and 27th, estimating the magnitude as 15.5 and 16, respectively. Helin and Alu photographed the comet on the 29th, 30th, and 31st. They estimated the magnitude as 17 on the 29th. The comet reached a maximum elongation of 163
on January 22. 654

cometography: a catalog of comets

Although several observatories followed the comet in February and March, there were only a few physical descriptions reported. Seki estimated the photographic magnitude as 16 on February 1, 17.5 on the 4th and 5th, and 17 on the 10th. T. Kojima (Chiyoda, Gunma, Japan) obtained two images using his 25-cm reflector on February 10 and estimated the magnitude as 16.5. Helin estimated the photographic magnitude as 16.5 on March 6, which ended up being the final observation of the year. Thereafter, the comet’s elongation decreased until it reached a minimum of 30
on September 26. Although no visual observations were made of this comet, A. Hale (New Mexico, USA) and R. J. Modic (Ohio, USA) did report several attempts during 1992 January 29 to April 29. They concluded that the comet never exceeded magnitude 13.5–14.5. The first observation of 1993 came on March 18, when A. C. Gilmore (Mt. John University Observatory, Lake Tekapo, New Zealand) obtained photographic exposures using a 61-cm reflector. He gave the nuclear magnitude as 19.0. The comet was last detected during March 22 and 23, when Gilmore photographed it using a 61-cm reflector. He acquired 50-minute exposures on March 22.65 and March 22.69. He acquired exposures of 61 minutes on March 23.65 and 51.5 minutes on March 23.69. The nuclear magnitude was given as 18.7 on the 22nd and 18.8 on the 23rd. The position on the final date was given as α = 15h 41.3m, δ = 60
150 (2000). The first parabolic orbit was calculated by S. Nakano and was published on 1992 January 28. He took seven positions from January 7–27 and determined the perihelion date as 1992 July 8.97. The first hyperbolic orbit was calculated by B. G. Marsden and was published on March 18. This used 35 positions from 1992 January 9 to February 29 and included perturbations by all nine planets. The result was a perihelion date of July 8.87 and an eccentricity of 1.00440. Marsden (1993) took 42 positions from the entire period of visibility and included full planetary perturbations to determine the perihelion date as July 8.69 and the eccentricity as 1.00415. The 9th edition of Marsden’s Catalogue of Cometary Orbits included original and future orbits for this comet. The original orbit was elliptical with a period of about 1.0 million years, while the future orbit was hyperbolic with an eccentricity of 1.00008. T ω Ω (2000.0) i q e 1992 Jul. 8.6877 (TT) 239.8431 288.9032 39.2638 3.016578 1.004149

absolute magnitude: H0 = 3.2, n = 8.6 (Meyer) full moon: Dec. 21, 1992 Jan. 19, Feb. 18, Mar. 18, Apr. 17, May 16, Jun. 15, Jul 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6, Mar. 8, Apr. 6 sources: E. F. Helin and J. T. Alu, IAUC, No. 5432 (1992 Jan. 21); T. Seki and S. Nakano, IAUC, No. 5439 (1992 Jan. 28); E. F. Helin, J. T. Alu, and 655

cometography: a catalog of comets

T. Seki, MPC, No. 19565 (1992 Feb. 18); T. Seki and B. G. Marsden, MPC, Nos. 19731, 19818 (1992 Mar. 18); T. Kojima and E. F. Helin, MPC, No. 19915 (1992 Apr. 17); A. C. Gilmore and B. G. Marsden, MPC, Nos. 22115, 22196 (1993 Jun. 4); A. Hale, ICQ, 14 (1992 Jul.), p. 76; R. J. Modic, ICQ, 14 (1992 Oct.), pp. 113–14; B. G. Marsden, CCO, 9th ed. (1994), p. 100; P. M. Kilmartin correspondence with G. W. Kronk (2011). C/1992 B1 Discovered: 1992 January 31.74 (Δ = 1.14 AU, r = 1.16 AU, Elong. = 65
) (Bradfield) Last seen: 1992 March 7.7 (Δ = 1.08 AU, r = 0.58 AU, Elong. = 32
) Closest to the Earth: 1992 February 21 (0.9844 AU) 1992 VII=1992b Calculated path: LUP (Disc), SCO (Feb. 1), CrA (Feb. 13), SGR (Feb. 21), MIC (Feb. 29), CAP (Mar. 1) W. A. Bradfield (Dernancourt, South Australia, Australia) discovered this comet on 1992 January 31.74. He estimated the magnitude as 10 and described the comet as diffuse, without condensation. The position was α = 16h 07.0m, δ = 41
330 (2000). Bradfield saw the comet again on February 1.77. S. D. Ryder and R. H. McNaught (Siding Spring Observatory, New South Wales, Australia) confirmed the discovery when they acquired four CCD images during February 2.67–2.76, using the 102-cm reflector. Ryder obtained another CCD image on February 3.74. Prediscovery images were reported by P. Camilleri (Cobram, Victoria, Australia). These were obtained on January 30.7, using a 35mm camera with an 85mm lens and Kodak T-Max 400 film. The comet was magnitude 10, with a diffuse coma 40 across. Only a few observatories were able to follow the comet because of its southerly declination. A. C. Gilmore (Mt. John University Observatory, Lake Tekapo, New Zealand) used a 61-cm reflector to obtain five images of the comet on February 5. G. Lowe (Perth Observatory, Bickley, Western Australia, Australia) obtained a photograph of the comet on February 10. McNaught and Ryder obtained three images of the comet on February 12. The comet attained its most southerly declination of 42
on February 6. The final astrometric positions were obtained by Gilmore during February 13.63–13.64, using a 61-cm reflector. His colleague and wife, P. M. Kilmartin, gave the position as α = 18h 02.4m, δ = 41
000 (2000) on the final image. All of the images were obtained in poor seeing, with increasing clouds. The last image was very weak. The elongation was then 56
. A few visual observations were reported around mid-February. A. F. A. L. Jones (Nelson, New Zealand) saw the comet with his 32-cm reflector on the 13th. He determined the magnitude as 10.1 and said the coma was slightly condensed and 10 across. Camilleri also saw the comet on this date using his 20-cm reflector. He determined the magnitude as 10.3 and said the coma was slightly condensed and 2.50 across. On the 14th, A. Hale (Las Cruces, New Mexico, USA) saw the comet using his 41-cm reflector. He estimated the magnitude as 9.5 and said the comet was slightly condensed. 656

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Camilleri got another look at the comet on this same date. He gave the magnitude as 10.3 and noted the slightly condensed coma was 20 across. The final visual observation was obtained on February 15, when Camilleri found the comet using his 20-cm reflector. He determined the magnitude as 10.5 and noted the coma was uncondensed and 20 across. When Gilmore obtained photographic exposures of two and three minutes of the comet’s predicted position with a 61-cm reflector on March 3.7, the comet was not present. Kilmartin was not able to locate the comet on the photographic plates, even though its predicted magnitude should have been around 7. The comet was now sitting low in the dawn sky, but exposures of 15 and 7 minutes were obtained by Gilmore on March 4.7, with the second exposure having to be cut short because of brightening twilight. Kilmartin found “a patch or irregular brightness” near the expected position of the comet. From the longer exposure, she noted the patch was elongated, roughly measuring 40 by 20 , with the long axis in PA 70
10
. Gilmore obtained exposures of 15 and 10 minutes on March 7.7, with the second exposure again being cut short because of twilight. Kilmartin found a “very faint patch, involved with star trails,” which was about 30 across. No further photographs were attempted. The predicted position at the time of the March 7 observation was α = 21h 19.6m, δ = 20
400 (2000). The first parabolic orbit was calculated by McNaught and was published on 1992 February 6. He used 10 positions from February 2–5 and determined the perihelion date as 1992 March 19.54. The only additional orbit was calculated by B. G. Marsden and was published on March 18. He used 19 positions from February 2–13 and determined the perihelion date as March 19.54. This orbit is given below. T 1992 Mar. 19.5392 (TT)

ω 15.3368

Ω (2000.0) 275.3503

i 20.2378

q 0.500157

e 1.0

absolute magnitude: H10 = 9.1 (Shanklin, 1998) full moon: 1991 Dec. 21, 1992 Jan. 19, Feb. 18, Mar. 18 sources: W. A. Bradfield, S. D. Ryder, and R. H. McNaught, IAUC, No. 5442 (1992 Feb. 2); S. D. Ryder, IAUC, No. 5444 (1992 Feb. 4); R. H. McNaught and P. Camilleri, IAUC, No. 5445 (1992 Feb. 6); S. D. Ryder, R. H. McNaught, A. C. Gilmore, MPC, Nos. 19565, 19654 (1992 Feb. 18); A. C. Gilmore, P. M. Kilmartin, A. F. A. L. Jones, A. Hale, and P. Camilleri, IAUC, No. 5469 (1992 Mar. 10); S. D. Ryder, R. H. McNaught, G. Lowe, A. C. Gilmore, P. M. Kilmartin, and B. G. Marsden, MPC, Nos. 19731, 19818 (1992 Mar. 18); A. F. A. L. Jones, ICQ, 14 (1992 Apr.), p. 42; P. Camilleri and A. Hale, ICQ, 14 (1992 Jul.), p. 76; J. D. Shanklin, JBAA, 108 (1998 Apr.), pp. 90, 93; P. M. Kilmartin correspondence with G. W. Kronk (2011). 657

cometography: a catalog of comets

88P/Howell Recovered: 1992 March 5.45 (Δ = 2.30 AU, r = 3.29 AU, Elong. = 174
) Last seen: 1994 February 11.15 (Δ = 3.29 AU, r = 3.25 AU, Elong. = 79
) 1993 II=1992c Closest to the Earth: 1993 October 13 (1.6384 AU) Calculated path: LEO (Rec), VIR (Jul. 26), LIB (Oct. 26), SCO (Dec. 1), OPH (Dec. 10), SGR (1993 Jan. 3), CAP (Feb. 12), AQR (Mar. 16), PSC (Apr. 26), CET (May 8), PSC (May 21), CET (Jun. 25), ARI (Jul. 1), TAU (Sep. 7), ARI (Sep. 13) A prediction for the return of this comet was calculated by S. Nakano (1989, 1990). He took 70 positions from 1981–1988 and included full planetary perturbations. After integrating the comet’s motion to this apparition, he predicted a perihelion date of 1993 February 26.10. The comet was recovered by S. M. Larson and J. V. Scotti (Kitt Peak National Observatory, Arizona, USA) during 1992 March 5.45–5.47, using the 229-cm reflector and a Cousins R filter. The CCD magnitude was given as 20.8 and the position on the first image was α = 11h 14.9m, δ = +11
220 (2000). They confirmed the observations using the 91-cm reflector during March 6.44–6.47 and March 7.39–7.41. The comet’s appearance on the 6th was described as “very slightly diffuse,” while the magnitude was 21.7–22.2. No further observations were reported during the remainder of 1992. After having moved northward since its recovery, the comet attained a declination of +14
on April 22 and then began a southward motion. It reached a minimum elongation of 1
on November 6. After having moved southward since last April, the comet attained its most southerly declination of 24
on 1993 January 14. The earliest observations of 1993 were made in July. Both Scotti and A. Nakamura (Kuma Kogen Astronomical Observatory, Ehime, Japan) acquired CCD images on the 22nd. Scotti determined the magnitude as 15.1 and the nuclear magnitude as 21.2, noting a coma 2.240 across and a tail extending about 1100 in PA 249
. Nakamura was using the 60-cm reflector. He determined the magnitude as 15.0, noting a coma 0.40 across and a tail extending toward PA 240
. Nakamura added that there was a “weak central condensation.” Images by Scotti on the 23rd revealed a magnitude of 14.4 and a nuclear magnitude of 20.4. He said a tail extended more than 130 in PA 248
. H. Mikuz (Ljubljana, Slovenia) used a 20-cm reflector, a CCD camera, and a V filter on the 25th and 29th, describing the comet’s appearance as diffuse, with condensation. He estimated the magnitude as 14.5 on the first night and said the coma was 20 across. On the second night, he gave the magnitude as 14.9 and the coma diameter as 1.50 . The only physical descriptions provided in August came from P. Pravec (Ondřejov Observatory, Czech Republic), Scotti, and Nakamura. Pravec was using an 18-cm reflector when he obtained five CCD images on the 14th. He gave the magnitude as 15.1–15.2, noting a coma 0.30 across and a tail extending 0.1
in PA 250
. Scotti acquired CCD images on the 17th, 658

cometography: a catalog of comets

which revealed a magnitude of 15.5 and a nuclear magnitude of 19.6. He said the coma was 1.180 across, while a tail extended over 140 in PA 250
. Nakamura detected the comet on the 24th and 27th, giving the magnitude as 15.8 and 15.6, respectively. On both nights, he reported a tail extending 270 toward PA 245
. The comet attained its most northerly declination of +16
on September 14. That same night, Scotti determined the magnitude as 15.6 and the nuclear magnitude as 19.6. He added that the coma was 4700 across, while the tail extended 140 in PA 250
. Images by Nakamura on the 25th and 26th revealed the magnitude as 16.1 and 16.0, respectively. The coma diameter was 0.30 on the 25th and 0.350 on the 26th. On the latter date, the tail extended toward PA 240
. Several observers provided physical descriptions in October. On the 11th, Nakamura determined the CCD magnitude as 16.2. He said the coma was 0.350 across, while the tail extended toward PA 240
. L. V. Zhuravleva (Crimean Astrophysical Observatory-Nauchnyj, Ukraine) obtained an image of the comet with the 40-cm Zeiss double astrograph on the 12th and judged the magnitude as 16.3. CCD images by Pravec and Nakamura were obtained on the 19th, with both astronomers giving the magnitude as 16.0. Pravec added that the coma was 0.30 across, while the tail extended 30 in PA 240
. Nakamura said the coma was 0.40 across and exhibited a tail extending 20 in PA 235
. Scotti acquired CCD images on the 20th, which revealed a nuclear magnitude of 20.2. He also measured the coma diameter as 3900 and said the tail extended about 140 in PA 251
. The comet was well placed for observations in November, as it reached a maximum elongation of 178
on the 4th. Nakamura gave the CCD magnitude as 15.7 on the 14th. He noted a coma 0.50 across. The CCD magnitude was estimated as 15.5 on the 15th by T. Kojima (Chiyoda, Gunma, Japan), using a 25-cm reflector. Two CCD images by Nakamura on the 18th revealed the magnitude 16.0. He added that the coma was 2100 across. Nakamura made the only observations in December, when he obtained two CCD images on the 12th. The magnitude was given as 17.4, while the coma was 1500 across. After having moved southward since mid-September, the comet attained a declination of +13
on December 13 and then began a northward motion. Nakamura and Scotti made the only observations of the comet in 1994. Nakamura determined the magnitude as 17.7 on January 4 and reported a coma diameter of 0.30 . On January 7, Scotti gave the magnitude as 17.7 and the nuclear magnitude as 21.4. He added that the coma was 2600 . Scotti said the main tail extended more than 1.60 in PA 238
, while a “broad fanshaped structure” extended between PA 61
and PA 252
. Images by Nakamura on February 2 revealed the magnitude as 18.1 and the coma diameter as 1500 . 659

cometography: a catalog of comets

The comet was last detected during February 11.13–11.15, when Scotti acquired three CCD images while using the 91-cm reflector. He gave the magnitude as 18.1–18.6 and the nuclear magnitude as 20.9. Scotti also reported that the coma was 5400 in diameter, while a tail extended more than 1.8’ toward PA 235
. The position on the last image was α = 2h 35.9m, δ = +15
200 (2000). Multiple apparition orbits have been calculated by B. G. Marsden (1996), Nakano (1999, 2001, 2004, 2005), P. Rocher (2000, 2001, 2003, 2004, 2005), and K. Kinoshita (2003, 2004). All of these calculations included full planetary perturbations, while only those published from 1999 onward solved for nongravitational effects. The general result was a perihelion date of February 26.09 and a period of 5.58 years. Most of the remaining calculations solved for nongravitational effects using positions from 1987 onward and gave terms within the following ranges: A1 = +0.36 to +0.47 and A2 = 0.0551 to 0.0229. The only exceptions were Kinoshita (2004) and Nakano (2005), who achieved better residuals by solving for three nongravitational terms that were in the following ranges: A1 = +0.39 to +0.47, A2 = 0.0551 to 0.0550, and A3 = +0.11 to +0.13. The orbit of Nakano (2005) is given below. T ω Ω (2000.0) i q e 1993 Feb. 26.0933 (TT) 234.7717 57.7265 4.3993 1.409107 0.552065

absolute magnitude: H0 = 10.3, n = 4.4, post-perihelion (Meyer) full moon: Feb. 18, Mar. 18, Apr. 17, May 16, Jun. 15, Jul 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6, Mar. 8, Apr. 6, May 6, Jun. 4, Jul. 3, Aug. 2, Sep. 1, Sep. 30, Oct. 30, Nov. 29. Dec. 28, 1994 Jan. 27, Feb. 26 sources: S. Nakano, Nakano Note, No. 534 (1989 May 15); S. Nakano, MPC, No. 16379 (1990 Jun. 8); S. M. Larson and J. V. Scotti, IAUC, No. 5472 (1992 Mar. 11); S. M. Larson and J. V. Scotti, MPC, Nos. 19915, 19917 (1992 Apr. 17); J. V. Scotti, MPC, No. 22439 (1993 Sep. 1); P. Pravec, J. V. Scotti, and A. Nakamura, MPC, No. 22520 (1993 Sep. 30); J. V. Scotti, H. Mikuz, and P. Pravec, ICQ, 15 (1993 Oct.), pp. 144, 168; A. Nakamura, P. Pravec, and J. V. Scotti, MPC, No. 22611 (1993 Oct. 30); A. Nakamura, MPC, No. 22713 (1993 Nov. 29); A. Nakamura, P. Pravec, and J. V. Scotti, ICQ, 16 (1994 Jan.), pp. 4, 22; A. Nakamura and J. V. Scotti, MPC, No. 22983 (1994 Feb. 26); A. Nakamura, ICQ, 16 (1994 Apr.), p. 65; T. Kojima, MPC, No. 24605 (1995 Feb. 15); B. G. Marsden, CCO, 11th ed. (1996), pp. 68–9; L. V. Zhuravleva, MPC, No. 30310 (1997 Aug. 18); S. Nakano, CCO, 13th ed. (1999), pp. 74–5; P. Rocher correspondence with G. W. Kronk (2000, 2001, 2003, 2004, 2005); S. Nakano, Nakano Note, No. 783 (2001 Apr. 26); K. Kinoshita correspondence with G. W. Kronk (2003, 2004); S. Nakano, Nakano Note, No. 1040 (2004 Mar. 21); S. Nakano, Nakano Note, No. 1324 (2005 Apr. 12). 660

cometography: a catalog of comets

C/1992 F1 Discovered: 1992 March 24.82 (Δ = 1.99 AU, r = 1.34 AU, Elong. = 37
) (Tanaka– Last seen: 1993 January 23.30 (Δ = 2.81 AU, r = 1.79 AU, Elong. = 172
) Machholz) Closest to the Earth: 1992 April 30 (1.7144 AU) Calculated path: PEG (Disc), LAC (Apr. 17), AND (Apr. 18), CAS (May 1), 1992 X=1992d CAM (May 27), LYN (Jun. 19), UMa (Aug. 1), LYN (Aug. 3), LMi (Sep. 7), LEO (Oct. 12), CNC (Dec. 5) Z. Tanaka (Yodoe, Tottori, Japan) discovered this comet on 1992 March 24.82, using his 20-cm reflector. He estimated the magnitude as 10 and said the coma was 20 across. The position was α = 21h 54.8m, δ = +12
550 (2000). Although there was no apparent motion during the visual observation, Tanaka obtained a four-minute exposure about 25 minutes later which apparently indicated the comet had a daily motion of over 4 degrees in either PA 20
or 200
. Details of the discovery were sent to the Japanese National Astronomical Observatory, but poor weather prevented a confirmation from Japan. S. Nakano forwarded the announcement to the Central Bureau for Astronomical Telegrams (Cambridge, Massachusetts, USA) on March 27, but, again, no confirmation followed. On March 31, word was received from D. E. Machholz (Colfax, California, USA) that he had discovered a probable comet of magnitude 9.4 on March 31.51, using his homemade 12-cm refractor. He described the object as diffuse, about 20 across, with some condensation. There was no tail. Machholz had spent 760 hours searching for comets since his discovery of C/1988 P1. The first confirmations of this comet came from A. Hale (Las Cruces, New Mexico, USA) and T. Seki (Geisei, Kochi, Japan). Using his 41-cm reflector, Hale spotted the comet on April 1.47 and determined the magnitude as 9.6. He described it as diffuse and somewhat condensed. Seki photographed the comet during April 1.79–1.83, using his 60-cm reflector, and estimated the magnitude as 9. The comet was well observed in April, with most observers reporting a moderately condensed coma throughout the month. Using 10  50 binoculars, J. E. Bortle (Stormville, New York, USA) indicated that the magnitude increased from 8.6 to 8.2 from the 6th to the 29th. He said the coma was 3.5–60 across. While using his 32-cm reflector on the 6th, he reported that “the inner 30% of the coma is rather strongly condensed” and noted a “possible faint outer halo.” With the same telescope on the 29th, Bortle said the coma was bright, circular, and well condensed,” with “no sign of nucleus or separate central [condensation].” R. J. Bouma (Groningen, Netherlands) observed with his 25-cm reflector and said the magnitude increased from 8.5 to 8.0 from the 7th to the 30th. He added that the coma diameter was 2.80 on the 7th and 2.50 during the remainder of the month. Using 10  50 binoculars, Hale gave the magnitude as 8.3 on the 4th, 8.6 on the 10th, and 8.5 on the 29th. He noted on the first night that there had been a distinct brightening since his confirming observation on the 1st. A. Nakamura (Kuma, Ehime, Japan) followed the comet with his 20-cm 661

cometography: a catalog of comets

reflector from the 2nd to the 28th and reported the magnitude varied from 8.2 to 8.6. He added that the coma diameter was 3–50 . The comet was most observed in May, with nearly 400 observations being reported to the International Comet Quarterly. It reached a maximum elongation of 47
on the 6th and continued to show a moderately condensed appearance during the month. The highlight of the month was an unexpected outburst in brightness. J. D. Shanklin (1998) wrote that the outburst occurred between May 9.0 and May 9.9 and amounted to “just over a magnitude.” The outburst is obvious in the observations of several experienced observers. A. Ishikawa (Japan) reported the magnitude as 8.6 on the 1st and 7.2 on the 11th, using 20  100 binoculars. G. W. Kronk (Troy, Illinois, USA) judged the magnitude as 8.8 on the 7th and 7.8 on the 9th, using 20  80 binoculars. Bortle gave the magnitude as 8.5 on the 7th and 7.0 on the 12th, using 10  50 binoculars. H. Mikuz (Ljubljana, Slovenia) gave the magnitude as 9.0 on the 8th and 7.5 on the 13th, using 20  60 binoculars. R. J. Modic (Ohio, USA) determined the magnitude as 8.8 on the 7th, 8.3 on the 9th, and 7.6 on the 10th, using his 20-cm reflector. The coma seemed unchanged in appearance by the outburst, with most observers reporting a diameter of 4–60 . The comet slowly faded during the remainder of May, with Bortle giving magnitudes of 7.5 on the 19th, 7.7 on the 20th and 21st, 7.9 on the 23rd, and 8.0 on the 29th. He used 20  80 binoculars for these observations and generally noted that the coma diameter increased from 3.50 to 4.80 . A number of visual observers reported seeing the tail during the month. G. Keitch (England) saw it with 20  100 binoculars on the 11th and 24th. He said it extended 80 in PA 297
on the first night and 50 in PA 317
on the second night. The comet attained its most northerly declination of +66
on June 1. The number of observations greatly decreased in June, being a combination of the comet’s decreasing brightness and decreasing elongation from the Sun. Bouma indicated a fading from 8.6 to 10.4 during the 3rd to the 25th. Modic said the comet faded from 9.4 on the 3rd to 11.4 on the 29th. Both observers described the coma as slightly condensed, with Bouma noting that the diameter decreased from 3.20 to 2.20 and Modic noting that it decreased from 2.40 to 0.90 . Very few observations were made during the remainder of 1992. The final visual observations were made on July 2 and 3 by G. T. Nowak (Vermont, USA) and C. S. Morris (California, USA), respectively. Nowak was using 11  80 binoculars and determined the magnitude as 8.8, adding that the coma was slightly condensed and 40 across. Morris was using his 26-cm reflector and estimated the magnitude as 10.0. He said the coma was very slightly condensed and 3.50 across. The comet reached a minimum elongation of 29
on August 1. No observatories followed the comet during July through October. J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) obtained three CCD images using the 91-cm reflector on both November 28 and 30. His provided a physical description of the comet on 662

cometography: a catalog of comets

the first night, noting a magnitude of 18.2, a nuclear magnitude of 21.4, and a coma diameter of 2000 . Scotti added that the “tail curves through PA 344
0.80 from the nucleus to at least 2.30 in PA 1
.” Mikuz obtained CCD exposures of 10 and 15 minutes on December 27, using a 19-cm flat-field camera, but no trace of the comet was found. He suggested the comet was probably fainter than magnitude 17.0. The first observation of 1993 was made by Seki on January 2. He estimated the photographic magnitude as 19. The comet reached a maximum elongation of 173
on January 20. The comet was last detected during January 23.24–23.30, when Scotti obtained three CCD images using the 91-cm reflector. He gave the magnitude as 18.1–18.2 and the nuclear magnitude as 21.0. Scotti said the coma was 1800 across, while a tail extended 3.700 in PA 5
. He added that a broad, fan bracketed the tail between PA 331
and PA 24
. The position on the last image was α = 8h 07.3m, δ = +26
490 (2000). The first orbit was calculated by B. G. Marsden and was published on 1992 April 3. This used eight positions from March 24 to April 2 and determined the perihelion date as 1992 April 22.45. The first elliptical orbit was calculated by Marsden and was published on June 15. Marsden used 106 positions from April 1 to May 30 and included perturbations by all nine planets. The result was a perihelion date of April 22.69 and a period of about 4702 years. Marsden published a revised orbit on December 9. This used 140 positions from April 1 to November 30 and included full planetary perturbations. The result was a perihelion date of April 22.69 and a period of about 5369 years. Two orbits have been published using positions spanning the comet’s entire period of visibility. Marsden (1993) took 144 positions and included perturbations by all nine planets. The result was a perihelion date of 1992 April 22.69 and a period of about 5530 years. S. Nakano (1995) took 154 positions and included full planetary perturbations. He determined the perihelion date as April 22.69 and the period as about 5529 years. Nakano’s orbit is given below. Nakano also noted that the original and future orbits were elliptical with periods of about 5011 years and 5084 years, respectively. T ω Ω (2000.0) i q e 1992 Apr. 22.6902 (TT) 65.4745 300.5084 79.2924 1.261498 0.995966

absolute magnitude: pre-perihelion H0 = 6.0, n = 4.0, post-perihelion H0 = 4.0, n = 8.0 (Green, 1995) full moon: Mar. 18, Apr. 17, May 16, Jun. 15, Jul. 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6 sources: D. Machholz, Z. Tanaka, S. Nakano, A. Hale, and B. G. Marsden, IAUC, No. 5487 (1992 Apr. 1); T. Seki and B. G. Marsden, MPC, Nos. 19916, 19980 (1992 Apr. 17); D. Machholz, SACNEWS, Issue 184 (1992 May), p. 5; 663

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B. G. Marsden, MPC, No. 20121 (1992 May 16); B. G. Marsden, MPC, No. 20309 (1992 Jun. 15); J. E. Bortle, A. Hale, and H. Mikuz, ICQ, 14 (1992 Jul.), pp. 63, 76–9; G. W. Kronk and R. J. Modic, ICQ, 14 (1992 Oct.), pp. 114–17; J. V. Scotti and B. G. Marsden, MPC, Nos. 21159, 21165, 21235 (1992 Dec. 9); A. Nakamura, H. Mikuz, G. T. Nowak, and C. S. Morris, ICQ, 15 (1993 Jan.), pp. 5, 27; T. Seki, J. V. Scotti, and B. G. Marsden, MPC, Nos. 21631, 21637, 21758 (1993 Mar. 8); A. Ishikawa, ICQ, 15 (1993 Oct.), p. 162; R. J. Bouma, ICQ, 16 (1994 Apr.), pp. 44–5; G. Keitch, ICQ, 17 (1995 Jan.), p. 21; D. W. E. Green, ICQ, 17 (1995 Oct.), pp. 168–78; S. Nakano, Nakano Note, No. 1488 (1995 Oct. 21); J. D. Shanklin, JBAA, 108 (1998 Apr.), pp. 91–2; D. E. Machholz correspondence with G. W. Kronk (2008); D. E. Machholz correspondence with G. W. Kronk (2011). 105P/1992 G1 Recovered: 1992 April 1.35 (Δ = 1.69 AU, r = 2.54 AU, Elong. = 141
) (Singer Brewster) Last seen: 1993 September 16.25 (Δ = 2.08 AU, r = 3.02 AU, Elong. = 154
) Closest to the Earth: 1992 March 15 (1.6564 AU) 1992 XXVI=1992e Calculated path: SEX (Rec), LEO (Apr. 17), VIR (Jul. 12), LIB (Oct. 3), SCO (Nov. 14), OPH (Nov. 22), SGR (Dec. 24), CAP (1993 Feb. 25), AQR (Mar. 14) A prediction for the return of this comet was published by S. Nakano (1987, 1989). Nakano used 45 positions from the 1986 discovery apparition and included full planetary perturbations. After integrating the comet’s motion to this apparition, he determined the perihelion date as 1992 October 28.15. J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) recovered this comet on two CCD images obtained during 1992 April 1.35–1.37, using the 91-cm reflector. He determined the magnitude as 20.4. The position on the first image was α = 10h 11.5m, δ = +4
490 (2000). Three more images were obtained with the same equipment during April 4.28–4.32. Scotti gave the magnitude as 20.6 and said the last image revealed the comet as “very slightly diffuse” with a coma 800 across. No further observations were reported in 1992. After having moved northward since its recovery, the comet attained a declination of +7
on May 14 and then began a southward motion. The comet reached a minimum elongation of 6
on December 6. It reached its most southerly declination of 17
on December 24. After moving northward since late December, the comet attained a declination of +1
on 1993 July 8 and then began a southerly motion. Scotti acquired CCD images on July 20 and 24. He provided a physical description on the first night, noting a magnitude of 20.9, a nuclear magnitude of 22.2, and a coma diameter of 900 . Scotti added that a tail extended 7200 in PA 262
. Additional CCD images were acquired by Scotti on August 16. He judged the magnitude as 20.3 and the nuclear magnitude as 22.2. Scotti said the coma was 1000 across, while a faint tail extended 7200 in PA 262
. The comet reached a maximum elongation of 171
on August 26. 664

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The comet was last detected during September 16.19–16.25, when Scotti obtained three CCD images using the 91-cm reflector. The magnitude was given as 20.1–20.6 and the nuclear magnitude was 22.6. Scotti added that the coma was 1000 across. The position on the last image was α = 21h 52.7m, δ = 4
320 (2000). Multiple apparition orbits have been calculated by B. G. Marsden (1992, 1997, 2005), P. Rocher (1995, 1999, 2006), K. Kinoshita (1999, 2008, 2012), and Nakano (2002, 2005, 2009, 2012, 2015). All of these calculations included full planetary perturbations, while only those from 2005 onward solved for nongravitational effects. The general result was a perihelion date of October 27.25 and a period of 6.43 years. The nongravitational terms were within the following ranges: A1 = +0.21 to +0.38 and A2 = 0.0707 to 0.0660. The orbit of Nakano (2015) is given below. T ω Ω (2000.0) i q e 1992 Oct. 27.2539 (TT) 46.6507 192.6164 9.1925 2.026680 0.413759

absolute magnitude: H10 = 15 (Meyer) full moon: Mar. 18, Apr. 17, May 16, Jun. 15, Jul. 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6, Mar. 8, Apr. 6, May 6, Jun. 4, Jul. 3, Aug. 2, Sep. 1, Sep. 30 sources: S. Nakano, Nakano Note, No. 497 (1987 Aug. 20); S. Nakano, MPC, No. 14595 (1989 May 20); J. V. Scotti and B. G. Marsden, IAUC, No. 5490 (1992 Apr. 4); J. V. Scotti, MPC, No. 19916 (1992 Apr. 17); J. V. Scotti, MPC, No. 22439 (1993 Sep. 1); J. V. Scotti, MPC, No. 22520 (1993 Sep. 30); J. V. Scotti, ICQ, 15 (1993 Oct.), pp. 144, 168; P. Rocher correspondence with G. W. Kronk (1995, 1999, 2006); B. G. Marsden, CCO, 12th ed. (1997), pp. 72–3; K. Kinoshita correspondence with G. W. Kronk (1999, 2008, 2012); S. Nakano, Nakano Note, No. 853 (2002 May 8); B. G. Marsden, CCO, 16th ed. (2005), pp. 126–7; S. Nakano, Nakano Note, No. 1172 (2005 Mar. 17); S. Nakano, Nakano Note, No. 1762 (2009 Apr. 21); S. Nakano, Nakano Note, No. 2284 (2012 Jul. 24); S. Nakano, Nakano Note, No. 2869 (2015 Apr. 2). 135P/1992 G2 Prediscovery: 1992 March 30.72 (Δ = 1.91 AU, r = 2.74 AU, Elong. = 140
) (Shoemaker– Discovered: 1992 April 5.49 (Δ = 1.86 AU, r = 2.74 AU, Elong. = 144
) Levy 8) Last seen: 1993 September 16.17 (Δ = 2.68 AU, r = 3.57 AU, Elong. = 147
) Closest to the Earth: 1992 May 8 (1.7097 AU) 1992 XV=1992f Calculated path: LIB (Pre), SCO (Sep. 22), OPH (Oct. 5), SGR (Nov. 22), CAP (1993 Feb. 13), AQR (Mar. 7), CAP (Apr. 14), AQR (Apr. 22) In the course of the Palomar Asteroid and Comet Survey, C. S. Shoemaker, E. M. Shoemaker, and D. H. Levy (Palomar Observatory, California, USA) discovered this comet on films exposed during 1992 April 5.49, April 7.43–7.47, and April 8.35–8.36 while using the 46-cm Schmidt telescope. 665

cometography: a catalog of comets

They estimated the magnitude as 17.0 and noted a possible faint tail in PA 270
. The position on the first image was α = 15h 13.1m, δ = 17
060 (2000). At Siding Spring Observatory (New South Wales, Australia), R. H. McNaught found a prediscovery image on a photographic plate exposed on March 30.72 by A. Savage. The plate had been exposed using the 122-cm Schmidt telescope. There was a tail extending 3000 to the northwest. The position was α = 15h 14.2m, δ = 17
250 (2000). Several observatories followed the comet during the remainder of April, but only a few physical descriptions were reported. T. Seki (Geisei, Kochi, Japan) photographed the comet using his 60-cm reflector. He estimated the magnitude as 16 on the 11th, 16.5 on the 13th, and 16 on the 22nd. Film was exposed by C. S. Shoemaker, H. E. Holt, and Levy on the 26th. The magnitude was estimated as 17. Four observatories followed the comet during the remainder of 1992, but few physical descriptions were provided. E. F. Helin, J. T. Alu, and P. Rose (Palomar Observatory) photographed the comet on May 1 and 27, using the 46-cm Schmidt telescope. They estimated the magnitude as 16 on both nights. Photographs were obtained by Seki on May 2, 24, and 25. He estimated the magnitude as 15.5 on the first night and 17 on the last two nights. The Shoemakers, Levy, and G. J. Leonard photographed the comet on June 3, estimating the magnitude as 16. A photograph by the Shoemakers, Holt, and Leonard on June 25 revealed a magnitude of 16.7. The comet reached a maximum elongation of 178
on May 6. After having moved northward since its discovery, the comet attained a declination of 12
on June 27 and then began a southward motion. From July 4 to October 12, the comet was only observed by McNaught and D. I. Steel at Siding Spring Observatory using the 102-cm reflector. No descriptive information was provided during this time. The comet attained its most southerly declination of 19
on November 28. The comet reached a minimum elongation of 4
on 1993 January 4 and was lost in the Sun’s glare during the first few months of 1993. J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired three CCD images with the 91-cm reflector on the morning of May 30, when the comet was low in the southeastern sky. He determined the magnitude as 19.4–19.6 and the nuclear magnitude as 21.8. He reported a coma 800 across and a tail extending 0.230 in PA 247
. Scotti remained the only observer during the remainder of this comet’s apparition. He obtained three CCD images on July 21, giving the magnitude as 19.2 and the nuclear magnitude as 21.9. He added that the coma was 1200 across, while a tail extended less than 0.60 in PA 258
. Two CCD images on July 25 revealed a magnitude of 18.2–18.4 and a nuclear magnitude of 20.9. The coma was 1400 across, while the tail extended less than 0.60 in PA 250
. Scotti obtained two CCD images on August 15, which revealed a magnitude of 19.0 and a nuclear magnitude of 21.4. The coma was 1300 across and the tail extended 1.20 in PA 250
. After having moved northward 666

cometography: a catalog of comets

since last November, the comet attained its most northerly declination of 3
on July 6. It reached a maximum elongation of 172
on August 18. The comet was last detected during September 16.13–16.17, when Scotti acquired three CCD images using the 91-cm reflector. He determined the magnitude as 19.9–20.3 and the nuclear magnitude as 22.0. He added that the coma was 1200 in diameter. The position was α = 21h 24.8m, δ = 7
360 (2000). The first parabolic orbit was calculated by B. G. Marsden and was published on 1992 April 9. This used five positions from April 5–8 and determined a perihelion date of 1992 October 28.02. Marsden noted, “It is quite likely that the comet is a short-period one.” Marsden’s suspicion was confirmed on April 13, when S. Nakano calculated a short-period orbit using eight positions from March 30 to April 11. The perihelion date was given as 1992 May 21.03 and the period was 7.59 years. Nakano revised his calculations on April 25, when he used 11 positions from March 30 to April 22. The result was a perihelion date of 1992 June 15.55 and a period of 7.46 years. During the next few months and years, Nakano and Marsden revised their short-period orbits for this apparition, quickly establishing the period as 7.47 years. The only calculation to use positions spanning the entire period of visibility was by Marsden (1997). He determined the perihelion date as June 13.54. Multiple apparition orbits have been calculated by Marsden (1999), K. Kinoshita (1999), P. Rocher (1999, 2006), and Nakano (2004). All of these used full planetary perturbations. The result was a perihelion date of June 13.51–13.52 and a period of 7.47 years. The orbit of Nakano (2004) is given below. T ω Ω (2000.0) i q e 1992 Jun. 13.5152 (TT) 22.4062 213.3959 6.0534 2.710620 0.290713

absolute magnitude: H0 = 6.5, n = 7.9 (Meyer) full moon: Mar. 18, Apr. 17, May 16, Jun. 15, Jul 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6, Mar. 8, Apr. 6, May 6, Jun. 4, Jul. 3, Aug. 2, Sep. 1, Sep. 30 sources: C. S. Shoemaker, E. M. Shoemaker, D. H. Levy, and B. G. Marsden, IAUC, No. 5493 (1992 Apr. 9); A. Savage, R. H. McNaught, T. Seki, and S. Nakano, IAUC, No. 5495 (1992 Apr. 13); A. Savage, R. H. McNaught, C. S. Shoemaker, E. M. Shoemaker, D. H. Levy, T. Seki, and S. Nakano, MPC, Nos. 19916–17, 19980 (1992 Apr. 17); T. Seki and S. Nakano, IAUC, No. 5506 (1992 Apr. 25); T. Seki and S. Nakano, MPC, Nos. 20073, 20121 (1992 May 16); C. S. Shoemaker, H. E. Holt, D. H. Levy, T. Seki, E. F. Helin, J. T. Alu, P. Rose, and B. G. Marsden, MPC, Nos. 20194, 20309 (1992 Jun. 15); E. F. Helin, J. T. Alu, P. Rose, C. S. Shoemaker, E. M. Shoemaker, D. H. Levy, and G. J. Leonard, MPC, No. 20372 (1992 Jul. 14); 667

cometography: a catalog of comets

C. S. Shoemaker, E. M. Shoemaker, H. E. Holt, G. J. Leonard, R. H. McNaught, and D. I. Steel, MPC, No. 20546 (1992 Aug. 13); S. Nakano, Nakano Note, No. 579 (1993 Jan. 9); R. H. McNaught, D. I. Steel, and B. G. Marsden MPC, Nos. 20672, 20775 (1992 Sep. 12); R. H. McNaught and D. I. Steel, MPC, No. 20862 (1992 Oct. 11); R. H. McNaught and D. I. Steel, MPC, No. 20963 (1992 Nov. 10); J. V. Scotti, MPC, Nos. 22279, 22286 (1993 Aug. 2); J. V. Scotti, MPC, Nos. 22439–40 (1993 Sep. 1); J. V. Scotti, MPC, No. 22520 (1993 Sep. 30); J. V. Scotti, ICQ, 15 (1993 Oct.), p. 170; B. G. Marsden, CCO, 12th ed. (1997), pp. 38–9; B. G. Marsden, CCO, 13th ed. (1999), pp. 80–1; K. Kinoshita correspondence with G. W. Kronk (1999); P. Rocher correspondence with G. W. Kronk (1999, 2006); S. Nakano, Nakano Note, No. 1048 (2004 Apr. 6); B. A. Skiff correspondence with G. W. Kronk (2011); J. V. Scotti correspondence with G. W. Kronk (2013); S. Nakano correspondence with G. W. Kronk (2015). 149P/1992 G3 Discovered: 1992 April 9.35 (Δ = 1.80 AU, r = 2.66 AU, Elong. = 142
) (Mueller 4) Last seen: 1992 July 2.10 (Δ = 2.47 AU, r = 2.78 AU, Elong. = 97
) Closest to the Earth: 1992 April 2 (1.7958 AU) 1992 IV=1992g Calculated path: BOO (Disc), CVn (Apr. 28), BOO (Jun. 6) In the course of the Second Palomar Sky Survey, J. E. Mueller (Palomar Observatory, California, USA) found the trail of a possible comet on a photographic plate exposed for 90 minutes during 1992 April 9.35–9.41 by C. Brewer and herself using the 122-cm Schmidt telescope. The magnitude was estimated as 17.5. Mueller said the image was “softer than . . . those of some minor planets on the plate, with a possible hint of a tail to the west.” The position was α = 14h 13.1m, δ = +27
510 (2000). A 30-minute exposure was obtained during April 11.40–11.42, but the image was “too weak to confirm whether the object is cometary or not.” The photographic plate exposed on the 9th also happened to hold the discovery image of supernova 1992S. The first observation to confirm that this was a comet came from R. H. McNaught (Siding Spring Observatory, New South Wales, Australia). He photographed the comet using the 51-cm Uppsala Southern Schmidt telescope on April 12.67, estimating the magnitude as 17. He noted, “Object slightly diffuse; definitely cometary.” Four observatories followed the comet during the remainder of April; however, only T. Seki (Geisei, Kochi, Japan) provided physical descriptions. Using his 60-cm reflector, he photographed the comet and estimated the magnitude as 17 on the 14th, 17.5 on the 20th, and 18 on the 22nd. Three observatories continued to follow the comet in May and June; however, Seki continued to provide the only physical descriptions. He estimated the magnitude as 18.5 on May 3, 19 on May 10, 24, and 25, and 18.5 on May 26. Seki added that the coma was 800 across on May 10. The comet attained its most northerly declination of +30
on May 7. Seki estimated additional magnitudes of 19 on June 1 and 3. 668

cometography: a catalog of comets

The comet was last detected during July 2.08–2.10, when R. E. McCrosky and C.-Y. Shao (Oak Ridge Observatory, Massachusetts, USA) obtained two CCD images using the 155-cm reflector. No descriptive information was provided. The position on the last image was α = 14h 01.7m, δ = +23
260 (2000). The first orbit was calculated by B. G. Marsden and was published on 1992 April 15. This used seven positions from 1992 April 9–14, giving the perihelion date as 1992 January 27.56 and the period as 9.26 years. Ten days later, S. Nakano used ten positions from April 9–22 to determine the perihelion date as 1992 February 15.14 and the period as 9.06 years. As additional positions were reported, Nakano and Marsden published additional orbits during the next few months. Nakano calculated an orbit on September 12 that used positions spanning the entire period of visibility. The result was a perihelion date of 1992 February 16.36 and a period of 8.97 years. Multiple apparition orbits have been calculated by Nakano (2001, 2010), K. Kinoshita (2001), and P. Rocher (2001). All of these used positions from 1992–2001 and included full planetary perturbations. The result was a perihelion date of February 16.10–16.11 and a period of 8.97 years. The orbit of Kinoshita (2010) is given below. T ω Ω (2000.0) i q e 1992 Feb. 16.1036 (TT) 43.5198 145.4286 29.8028 2.636688 0.389405

absolute magnitude: H10 = 12.5 (Meyer) full moon: Mar. 18, Apr. 17, May 16, Jun. 15, Jul. 14 sources: J. E. Mueller and C. Brewer, IAUC, No. 5495 (1992 Apr. 13); R. H. McNaught, T. Seki, and B. G. Marsden, IAUC, No. 5497 (1992 Apr. 15); T. Seki and S. Nakano, IAUC, No. 5505 (1992 Apr. 25); J. E. Mueller, C. Brewer, R. H. McNaught, T. Seki, and S. Nakano, MPC, Nos. 20073, 20121 (1992 May 16); T. Seki and B. G. Marsden, MPC, Nos. 20194–5, 20309 (1992 Jun. 15); T. Seki and S. Nakano, MPC, Nos. 20372, 20481 (1992 Jul. 14); R. E. McCrosky and C.-Y. Shao, MPC, No. 20546 (1992 Aug. 13); S. Nakano, MPC, No. 20775 (1992 Sep. 12); S. Nakano, CCO, 14th ed. (2001), pp. 98–9; K. Kinoshita correspondence with G. W. Kronk (2001, 2010); P. Rocher correspondence with G. W. Kronk (2001); S. Nakano, Nakano Note, No. 771R (2001 Dec. 22). C/1992 J1 Discovered: 1992 May 1.15 (Δ = 4.51 AU, r = 5.46 AU, Elong. = 159
) (Spacewatch) Last seen: 1995 February 2.12 (Δ = 5.92 AU, r = 5.61 AU, Elong. = 67
) Closest to the Earth: 1993 December 10 (2.6590 AU) 1993 XV=1992h Calculated path: VIR (Disc), BOO (Dec. 4), CVn (1993 Feb. 17), UMa (Apr. 14), DRA (Oct. 23), CAM (Nov. 16), UMi (Dec. 3), CEP (Dec. 13), CAS (1994 Jan. 13), AND (Mar. 2), PER (May 21), AND (Sep. 8), TRI (Sep. 25), AND (Oct. 5), TRI (Oct. 6), PSC (Nov. 2) 669

cometography: a catalog of comets

This comet has the distinction of being the first comet discovered by a computer. The comet was first detected during 1992 May 1.15–1.19, when the 91-cm reflector (Steward Observatory, Kitt Peak, Arizona, USA) acquired three CCD images. Motion detection software identified the object; however, D. L. Rabinowitz noticed the coma and reported it as a comet. J. V. Scotti determined the magnitude as 18.7 and said the diffuse coma was 1400 across. The position on the first image was α = 13h 12.4m, δ = 8
310 (2000). Scotti acquired three more CCD images during May 2.27–2.29. These revealed a magnitude of 18.5 and a diffuse coma 1700 across. None of the images revealed a resolvable tail. Only two observatories followed the comet during the remainder of May. Scotti judged the magnitude as 18.2–18.5 on the 3rd. He noted a coma 1600 across and a faint tail extending 1700 in PA 146
. Also on the 3rd, T. Seki (Geisei, Kochi, Japan) photographed the comet with his 60-cm reflector. He estimated the magnitude as 19 and said the coma was 1000 across. Scotti determined the magnitude as 18.3–18.9 on the 4th, 18.5 on the 7th, and 18.2–18.7 on the 8th. Additional CCD images were acquired by Scotti on the 9th. The comet’s elongation steadily decreased following the discovery and the final observations of 1992 were made on June 2, when Scotti gave the magnitude as 18.3–18.8. The comet reached a minimum elongation of 10
on October 6. The first observations obtained in 1993 came from Scotti on January 1 and 23. For the first night, he reported the magnitude as 16.6 and the nuclear magnitude as 19.7, adding that the coma was 2000 across and the tail extended 0.520 in PA 200
. On the second night, he reported the magnitude as 16.1 and the nuclear magnitude as 19.0, adding that the coma was 2100 across and the tail extended 1.040 in PA 201
. A. Nakamura (Kuma Kogen Astronomical Observatory, Ehime, Japan) provided excellent details in February. He saw the comet both visually and by CCD using the 60-cm reflector on the 19th. His visual observation revealed a magnitude of about 14.7 and a coma 0.70 across. The CCD image revealed a magnitude of 15.4, a coma diameter of 0.40 , and a tail extending toward PA 205
. Nakamura visually spotted the comet again on February 25, judging the magnitude as 14.9 and reporting a coma diameter of 0.450 . The comet reached a maximum elongation of 136
on March 12. Physical descriptions were provided by both Scotti and Nakamura throughout March and April. Scotti acquired CCD images on March 3, which revealed a magnitude of 15.6 and a nuclear magnitude of 18.9. He added that the coma was 2300 across, while the tail extended 2.850 in PA 188
. On March 22, Nakamura judged the CCD magnitude as 15.4, noting a coma 0.30 across and a tail extending toward PA 195
. Additional CCD images by Scotti on March 28, revealed a magnitude of 15.3 and a nuclear magnitude of 18.2. He noted a coma 2300 across and a tail extending 2.930 in PA 170
. Another visual observation was made by Nakamura on April 1. He determined the 670

cometography: a catalog of comets

magnitude as 14.9 and noted a moderately condensed coma 0.60 across. Also on the 1st, Nakamura obtained a CCD image that revealed a magnitude of 15.6, a coma 0.40 across, and a tail extending toward PA 180
. A CCD image by Nakamura on April 14 revealed a magnitude of 15.5 and a coma 0.50 across. Another image on April 19 revealed a magnitude of 15.4, a coma 0.250 across, and a tail extending toward PA 155
. Scotti acquired two CCD images on April 21. These revealed a coma diameter of 1600 and a fan-shaped tail that was 10 long and extended toward PA 122
to PA 228
. After having moved northward since its discovery one year earlier, the comet attained a declination of +55
on May 17 and then began a southward motion. S. Nakano (Sumoto, Hyogo, Japan) acquired CCD images on May 14 and 15, using his 20-cm reflector. He determined the magnitude as 15.3–15.5 on the first night and 15.6 on the second night. E. Meyer and H. Raab (Linz, Austria) obtained CCD images on the 16th, using a 29-cm reflector. They judged the magnitude as 15.1–15.4. On the 20th, Nakamura obtained a CCD image that revealed a magnitude of 15.9 and a coma diameter of 0.3’. Nakano determined CCD magnitudes of 16.0 on the 23rd, 15.6–15.9 on the 24th, and 15.6 on the 25th. Meyer and Raab determined the magnitude as 15.4–15.8 on May 31. Meyer and Raab provided the majority of magnitude determinations in June and July, as the comet’s elongation decreased. They gave the magnitude as 15.3–15.4 on June 9, 14.7–15.0 on June 28, and 15.3 on July 3. The observations of July 3 were also the last before the comet became lost in the Sun’s glare. After having moved southward since mid-May, the comet attained a declination of +53
on July 25 and then began a northward motion. The comet reached a minimum elongation of 41
on August 5. T. Kojima (Chiyoda, Gunma, Japan) acquired the next image of the comet on November 11, when it was about 32
above the north-northeast horizon. He was using a 25-cm reflector and determined the CCD magnitude as 15.1. T. Urata (Nihondaira Observatory, Oohira Station, Japan) obtained CCD images of the comet on November 23 and 25, using a 31-cm reflector, giving magnitudes of 15.6 and 15.8, respectively. During December, CCD magnitudes were given as 15.7 by Kojima on the 4th, 15 by Urata on the 11th, 15.5 by Y. Ikari (Ohtsu, Shiga, Japan) on the 12th, 15 by Urata on the 17th, and 15.6 by Kojima on the 31st. Ikari was using a 26-cm reflector. The comet attained its most northerly declination of +88
on December 9 and a maximum elongation of 112
on December 18. The comet was fading as 1994 began, as it moved away from both the Sun and Earth. Ikari was the first to detect the comet, when he acquired a couple of CCD images on January 2. He estimated the magnitude as 15. Kojima and Ikari provided magnitudes of 15.4 and 15.5, respectively, on the 4th. Meyer, Raab, and E. Obermair used the 29-cm reflector to determine magnitudes of 15.3–15.5 on the 5th and 15.1–15.2 on the 15th. 671

cometography: a catalog of comets

On January 20, Kojima gave the magnitude as 15.8. Kojima acquired two more CCD images on February 1, giving the magnitude as 16.0–16.3. Nakamura determined the magnitude as 16.0 on the 3rd. He added that the coma was 0.350 across, while the tail extended toward PA 25
. Photographs by Seki on March 2 revealed an estimated magnitude of 16. Kojima determined the magnitude as 15.6 on March 6. No further observations were reported as the comet entered evening twilight. The comet reached a minimum elongation of 26
on May 13. It was next spotted in the morning sky by Kojima on August 13, when he judged the magnitude as 16.1. Nakamura gave the magnitude as 17.3 on August 15, adding that the coma was 0.30 across, while the tail extended toward PA 33
. Nakamura provided magnitudes of 17.0 on September 8 and about 17.5 on September 13. He noted a coma diameter of 0.350 and a tail extending toward PA 20
on the first night and a coma 0.250 across on the second night. K. Ito (Sengamine, Hyogo, Japan) acquired two CCD images on October 1, using a 20-cm reflector. He estimated the magnitude as 17.0 and said the coma was 0.30 across. Astronomers at Klet Observatory (Czech Republic) obtained a series of CCD images with the 57-cm reflector during October 9–11, consistently noting a magnitude of 17.8. Nakamura gave the magnitude as 17.2 on both October 14 and 30. He said the coma was 0.350 across on both nights, while a tail was noted on the second night that extended 1.00 in PA 25
. The comet reached a maximum elongation of 160
on October 29. Nakamura obtained two more CCD images on November 23, which revealed a magnitude of 17.5, a coma diameter of 0.450 , and a tail extending 0.80 in PA 33
. S. M. Larson (Catalina Station, Mt. Bigelow, Arizona, USA) acquired five CCD images of the comet on December 1, using the 154-cm reflector, giving the magnitude as 17.8–18.1. Ito determined the magnitude as 17.4 and the coma diameter as 0.50 on December 4. Nakamura estimated the magnitude as 18.5 on December 29 and said the coma was 0.30 across. Two sets of observations were made in 1995 January. Scotti obtained CCD images on the 3rd, giving the magnitude as 18.4–18.5 and the nuclear magnitude as 21.3. Larson and C. W. Hergenrother (Kitt Peak National Observatory, Arizona, USA) acquired three CCD images while using the 229-cm reflector on the 29th. They determined the magnitude as 19.2. The comet was last detected during February 2.11–2.12, when Scotti acquired three CCD images using the 91-cm reflector. He judged the magnitude as 19.0–19.6 and the nuclear magnitude as 22.1. The position on the last image was α = 1h 00.7m, δ = +15
310 (2000). Hergenrother acquired a CCD image of the comet’s predicted position on 1996 January 21, using the 229-cm reflector. No trace of the comet was found, prompting him to estimate that it was fainter than magnitude 23.0. The first parabolic orbit was calculated by B. G. Marsden and was published on 1992 May 4. This used 13 positions from May 1–4. The result was a perihelion date of 1993 September 7.65. Marsden published a revision 672

cometography: a catalog of comets

on June 15, which used 23 positions from May 1 to June 2. This determined the perihelion date as September 6.32. A hyperbolic orbit was published by Nakano on 1993 March 8. This used 41 positions from 1992 May 1 to 1993 February 18 and included full planetary perturbations. The result was a perihelion date of September 5.55 and an eccentricity of 1.00001. The first elliptical orbit was calculated by Nakano and was published on May 6. This used 78 positions from 1992 May 1 to 1993 April 15. The result was a perihelion date of 1993 September 5.55 and a period of about 26 million years. Nakano published revisions on 1994 February 26 and 1994 September 19, which gave the period as about 30 million years and 25 million years, respectively. Two orbits have been published using positions spanning the entire period of visibility and including full planetary perturbations. Nakano (1995) used 214 positions, calculating a perihelion date of September 5.55 and a period of about 22 million years. Nakano also found the original and future orbits were elliptical with periods of about 14 million years and 80 thousand years, respectively. M. Królikowska (2014) used 248 positions, calculating a perihelion date of September 5.55 and a period of about 23 million years. This orbit is given below. Królikowska also found the original and future orbits were elliptical with periods of about seven million years and 78 thousand years, respectively. T ω Ω (2000.0) i q e 1993 Sep. 5.5478 (TT) 83.4010 203.3241 124.3187 3.007007 0.999963

absolute magnitude: H0 = 8.3, n = 3.7 (Meyer) full moon: Apr. 17, May 16, Jun. 15, Jul 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6, Mar. 8, Apr. 6, May 6, Jun. 4, Jul. 3, Aug. 2, Sep. 1, Sep. 30, Oct. 30, Nov. 29. Dec. 28, 1994 Jan. 27, Feb. 26, Mar. 27, Apr. 25, May 25, Jun. 23, Jul. 22, Aug. 21, Sep. 19, Oct. 19, Nov. 18, Dec. 18, 1995 Jan. 16, Feb. 15 sources: D. L. Rabinowitz and J. V. Scotti, IAUC, No. 5509 (1992 May 2); J. V. Scotti, T. Seki, and B. G. Marsden, IAUC, No. 5513 (1992 May 4); J. V. Scotti, T. Seki, and B. G. Marsden, MPC, Nos. 20073, 20121 (1992 May 16); J. V. Scotti and B. G. Marsden, MPC, Nos. 20195, 20310 (1992 Jun. 15); J. V. Scotti and S. Nakano, MPC, Nos. 21631–2, 21637, 21758 (1993 Mar. 8); A. Nakamura, ICQ, 15 (1993 Apr.), p. 75; J. V. Scotti, MPC, Nos. 21834, 21837 (1993 Apr. 6); J. V. Scotti and S. Nakano, MPC, Nos. 21982, 21989, 22029 (1993 May 6); J. V. Scotti, S. Nakano, E. Meyer, and H. Raab, MPC, Nos. 22115–6, 22121 (1993 Jun. 4); A. Nakamura, ICQ, 15 (1993 Jul.), p. 125; A. Nakamura, S. Nakano, E. Meyer, and H. Raab, MPC, No. 22279 (1993 Aug. 2); S. Nakano, ICQ, 15 (1993 Oct.), p. 162; T. Urata, MPC, No. 22713 (1993 Nov. 29); T. Urata, Y. Ikari, S. Nakano, E. Meyer, E. Obermair, H. Raab, and A. Nakamura, MPC, Nos. 22988, 23105 (1994 Feb. 26); 673

cometography: a catalog of comets

A. Nakamura, ICQ, 16 (1994 Apr.), p. 46; T. Seki, MPC, No. 23365 (1994 May 25); A. Nakamura and S. Nakano, MPC, Nos. 23882, 23955 (1994 Sep. 19); [Klet[, MPC, No. 24134 (1994 Nov. 18); S. M. Larson and J. V. Scotti, MPC, No. 24423 (1995 Jan. 16); T. Kojima, J. V. Scotti, S. M. Larson, and C. W. Hergenrother, MPC, No. 24598 (1995 Feb. 15); A. Nakamura and K. Ito, ICQ, 17 (1995 Apr.), p. 58; T. Kojima, MPC, No. 24934 (1995 Apr. 15); S. Nakano, Nakano Note, No. 1490 (1995 Jun. 4); T. Kojima, MPC, No. 25246 (1995 Jun. 13); C. W. Hergenrother, ICQ, 18 (1996 Jul.), p. 129; M. Królikowska, AAP, 567 (2014 Jul.), A126, 31pp; J. V. Scotti correspondence with G. W. Kronk (2016). C/1992 J2 Discovered: 1992 May 3.81 (Δ = 0.87 AU, r = 0.76 AU, Elong. = 47
) (Bradfield) Last seen: 1992 June 4.45 (Δ = 0.94 AU, r = 0.63 AU, Elong. = 37
) Closest to the Earth: 1992 May 18 (0.4939 AU) 1992 XIII=1992i Calculated path: CET (Disc), ERI (May 15), ORI (May 21), MON (May 27), GEM (May 31), CMi-GEM (Jun. 1) W. A. Bradfield (Dernancourt, South Australia, Australia) discovered this comet on 1992 May 3.81 while searching for comets. He estimated the magnitude as 10 and described the comet as diffuse, without a central condensation. The position was α = 0h 23.1m, δ = 15
410 (2000). The comet was confirmed the next night by A. C. Gilmore and P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) and by R. H. McNaught and D. I. Steel (Siding Spring Observatory, New South Wales, Australia). Gilmore and Kilmartin were using a 61-cm reflector and photographed the comet on May 4.74 and May 4.76. They noted a round, moderately condensed coma about 30 across, with a bright central condensation, but no tail. McNaught and Steel photographed the comet using the 51-cm Uppsala Southern Schmidt on May 4.79 and May 4.80. They reported the coma was 10 across, while a tail extended 30 toward the southwest. The comet attained its most southerly declination of 15.7
on May 5 and then began a northerly motion. It was also moving into twilight. G. J. Garradd (Tamworth, New South Wales, Australia), D. A. J. Seargent (The Entrance, New South Wales, Australia), and P. Camilleri (Cobram, Victoria, Australia) visually observed the comet on the 5th. Garradd was using his 25-cm reflector and gave the magnitude as 9.4. Seargent saw the comet with his 25  100 binoculars. He gave the magnitude as 9.3 and said the coma was 30 across. Camilleri was using 20  80 binoculars. He judged the magnitude as 9.5, noting a coma 20 across. All three observers described the coma as moderately condensed. McNaught obtained additional images of the comet on May 5, but no descriptive information was provided. Camilleri determined the magnitude as 9.4 on the 9th and said the coma was 20 across. Seargent also gave the magnitude as 9.4 on the 12th and said the coma was 30 across. The comet reached a minimum elongation of 26
on May 20. 674

cometography: a catalog of comets

With the comet rapidly moving into twilight, the only precise positions had made on May 4 and 5, while rough positions had been reported by Bradfield for May 3, T. B. Tregaskis (Mt. Eliza, Victoria, Australia) for May 6 and 10, and Camilleri for May 9. D. Herald (Australia) knew how important it was to direct observers to the right area of the sky when the comet exited twilight, so he took the available positions and determined an orbit, as well as ephemerides. In looking at Herald’s ephemeris, M. P. Candy (Perth Observatory, Bickley, Western Australia, Australia) checked the observatory’s survey photographs obtained using a camera with a 300-mm lens and noted a trailed image of the comet had been registered on May 11. The beginning and end of the trail were measured and sent to B. G. Marsden (Central Bureau for Astronomical Telegrams, Cambridge, Massachusetts, USA). Marsden was able to use these, along with the earlier precise positions, and produced a revised orbit and ephemeris that enabled the comet to be recovered after perihelion on May 29. Gilmore obtained the first images and said a 61-cm reflector revealed the comet as “large and diffuse, with no obvious central condensation.” A few hours later, G. Lowe (Perth Observatory) photographed the comet with the 33-cm astrograph and described it as “a faint blob about 2000 across.” Gilmore obtained two more photographs of the comet on May 30 and again noted large and diffuse images, with no obvious condensation. The last observations of this comet were obtained on June 2.45 and June 4.45, when Lowe operated the 33-cm astrograph to expose photographic plates. No physical description was provided. The position on the last date was α = 7h 25.8m, δ = +14
250 (2000). The comet reached a maximum elongation of 37
on June 4. The first parabolic orbit was calculated by Herald and was published on 1992 May 18. It used the available positions and gave the perihelion date as 1992 May 26.76. Marsden never published his initial orbit that enabled the comet to be located on May 29, but he did publish an orbit using 10 positions from May 4–29. The resulting perihelion date was May 25.79. Marsden published a revised orbit on July 14. It used 10 positions from May 4 to June 4 and determined the perihelion date as May 25.79. This orbit is given below. T 1992 May 25.7940 (TT)

ω 299.7170

Ω (2000.0) 159.9981

i 158.5644

q 0.592305

e 1.0

absolute magnitude: H10 = 12.5, maximum at T15 days (Meyer) full moon: Apr. 17, May 16, Jun. 15 sources: W. A. Bradfield, A. C. Gilmore, P. M. Kilmartin, R. H. McNaught, and D. I. Steel, IAUC, No. 5514 (1992 May 4); R. H. McNaught, G. J. Garradd, and D. A. J. Seargent, IAUC, No. 5516 (1992 675

cometography: a catalog of comets

May 7); W. A. Bradfield, T. B. Tregaskis, P. Camilleri, and D. Herald, IAUC, No. 5524 (1992 May 18); D. Herald, M. P. Candy, B. G. Marsden, A. C. Gilmore, and G. Lowe, IAUC, No. 5530 (1992 May 30); A. C. Gilmore, P. M. Kilmartin, R. H. McNaught, M. P. Candy, and G. Lowe, MPC, No. 20195 (1992 Jun. 15); M. P. Candy, G. Lowe, and B. G. Marsden, MPC, Nos. 20372, 20481 (1992 Jul. 14); P. Camilleri, ICQ, 14 (1992 Oct.), p. 117; G. Lowe correspondence with G. W. Kronk (2011). 47P/Ashbrook– Recovered: 1991 April 24.05 (Δ = 3.71 AU, r = 4.70 AU, Elong. = 170
) Jackson Last seen: 1997 February 1.44 (Δ = 4.56 AU, r = 5.33 AU, Elong. = 138
) Closest to the Earth: 1993 October 5 (1.4012 AU) 1993 XIII=1992j Calculated path: VIR (Rec), LIB (Oct. 18), SCO (1992 Jan. 1), LUP (Jun. 25), SCO (Aug. 25), SGR (Nov. 13), CAP (1993 Jan. 25), AQR (Mar. 14), PSC (May 20), CET (Jun. 9), PSC (Jul. 4), ARI (1994 Feb. 9), TAU (Apr. 16), AUR (May 25), GEM (Aug. 8), LYN (Oct. 12), AUR (1995 Jan. 11), GEM (Mar. 19), CNC (Jun. 16), LEO (Aug. 27), VIR (1996 Nov. 16) G. Forti (1989) and S. Nakano (1990) provided predictions for the return of this comet. Forti used 298 positions from 1970–1988, while Nakano used 367 positions from 1948–1988. Both astronomers included full planetary perturbations and solved for nongravitational forces. Both predicted a perihelion date of 1993 July 14.05. This comet was recovered by A. C. Gilmore and P. M. Kilmartin (Mt. John University Observatory, Lake Tekapo, New Zealand) on 1992 May 4.58 and May 4.62. They were using a 61-cm reflector and acquired 40-minute exposures that revealed weak, stellar images of magnitude 18.9. The position on the first image was α = 16h 52.8m, δ = 37
460 (2000). More convincing images were obtained with the same telescope on May 29.57 and May 29.60, with exposure times of 40 and 42 minutes, respectively. The magnitude was given as 17.5. No further observations were made during the remainder of 1992. These positions confirmed a single-night detection on 1991 April 24.05 and April 24.09, that had been reported by M. Lindgren and G. Tancredi (La Palma Observatory, Canary Islands) using the 256-cm Nordic Optical Telescope. The position on the first image was α = 13h 29.8m, δ = 16
550 (2000). J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton (2000) analyzed the La Palma images as part of a program to study cometary nuclei. They said the “comet looks stellar,” giving the V magnitude as 21.5 and the R magnitude as 21.1. They determined that the radius of the nucleus was 3.0 kilometers. The comet moved northward after the observation at La Palma Observatory. It attained a declination of 15
on 1991 June 27 and then began a southerly motion. The comet reached a minimum elongation of 7
on November 8. It then attained its most southerly declination of 38
on 1992 May 30 and reached a maximum elongation of 164
on June 1. 676

cometography: a catalog of comets

The comet was lost in the Sun’s glare as 1993 began, passing 8
from the Sun on January 18. The first observations of the year came on May 10 and 11, when R. H. McNaught and D. I. Steel (Siding Spring Observatory, New South Wales, Australia) acquired two CCD images on each night, using the 102-cm reflector. No descriptive information was provided. The next observations came on June 25, when J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired two CCD images using the 91-cm reflector. He determined the magnitude as 14.0 and the nuclear magnitude as 17.9. Scotti said the coma was 2400 across and exhibited a broad tail that extended from PA 245
to PA 301
near the nucleus. The tail curved sharply, extending 16.90 in PA 241
with a width of 1.30 . Scotti also noted a “sharp tailward spike” that extended 0.670 in PA 250
. Visual observations began in July. R. J. Modic (Ohio, USA) said the comet was at the limit of visibility in his 20-cm reflector on the 17th. He judged the magnitude as 13.2 and described the coma as very slightly condensed and 1.0’ across. W. C. Morrison (Canada) and A. Hale (New Mexico, USA) independently saw the comet on the 21st. Morrison was using a 45-cm reflector. He gave the magnitude as 13.3 and said the coma was slightly condensed and 0.90 across. Hale was using his 41-cm reflector and determined the magnitude as 12.7. Hale still reported the magnitude as 12.7 on the 25th. Morrison gave the brightness as 12.6 on the 28th, adding that the coma was slightly condensed and 1.90 across. R. J. Bouma (Netherlands) used his 25-cm reflector to observe the comet on July 29. He determined the magnitude as 12.8 and said the coma was very slightly condensed and 0.80 across. Scotti acquired two sets of CCD images on the 22nd and 23rd. On the first night, Scotti estimated the magnitude as 15.5 and the nuclear magnitude as 20.7. He reported a coma 2700 across, noting a “tail curving through PA 258
at 0.80 , continuing through PA 249
at 4.90 and out to 8.70 at PA 245
.” On the second night, Scotti gave the magnitude as 13.4 and the nuclear magnitude as 18.9. He added that the coma was 3000 across. Scotti reported a “tail curving through PA 267
at 0.60 from the nucleus, continuing through PA 249
at 2.40 and out to 18.90 at PA 241
.” A “sharp tailward spike” extended about 1.340 in PA 245
. The full moon prevented observations during early August, but the comet was detected by T. Kobayashi (Oizumi, Gunma, Japan) on the 11th and 12th, using a 16-cm reflector and a CCD camera. No physical descriptions were provided. P. Pravec (Ondřejov Observatory, Czech Republic) acquired CCD images using an 18-cm reflector on the 12th and 13th. On the latter night, he determined the magnitude as 12.7 and said the coma was “well condensed” and 0.50 across. Pravec added that the “tail system” spanned PA 214–306
, with lengths of 0.90 in PA 214
, 1.20 in PA 228
, 2.30 in PA 240
, 4.80 in PA 249
, 2.80 in PA 254
, 2.10 in PA 275
, 0.90 in PA 293
, and 0.50 in PA 306
. Scotti also acquired images of the comet on the 13th. He gave the magnitude as 13.4 and the nuclear magnitude as 17.4. Scotti reported a fan-shaped tail that curved “from PA 274
at a distance of 677

cometography: a catalog of comets

0.570 from the nucleus, and continues as a narrow tail 22.00 in PA 243
.” There was also “a sharp tailward spike” that extended 2.00 in PA 248
. C. S. Morris (California, USA) visually spotted the comet on the 14th and 15th, using his 26-cm reflector. He determined the magnitude as 12.3 and 12.5, respectively, and noted a slightly condensed coma 1.20 across. For both nights, Morris said the coma was elongated toward the west. On the 17th, Bouma gave the magnitude as 12.7, describing the coma as very slightly condensed and 1.20 across. Bouma next saw the comet on the 19th. He determined the magnitude as 12.8 and said the coma was very slightly condensed and 1.00 across. On the 21st, Morris and Hale observed the comet and gave the magnitude as 12.5. Morris added that the coma was slightly condensed and 1.60 across. Modic observed the comet on the 22nd and 26th, giving the magnitude as 13.7–13.8 and the coma diameter as 0.5–0.70 . Nakamura visually observed the comet with the 60-cm reflector on August 27. He gave the magnitude as 13.1 and said the coma was moderately condensed and 0.90 across. Nakamura added that the tail extended about 40 in PA 250
. Although the comet was moving away from the Sun, it was still heading toward its closest approach to Earth in September. Bouma gave the magnitude of 12.6 on the 11th and said the coma was uncondensed and 1.20 across. A CCD image by Scotti on the 14th revealed a magnitude of 13.2, a coma diameter of 1.320 , and a tail extending 0.46
in PA 241
. Bouma determined the magnitude as 12.8 and 12.5 on the 17th and 18th, respectively, adding that the coma was slightly condensed and 1.0–1.20 across. Morris also saw the comet on the 18th, giving the magnitude as 12.3. He also described the coma as slightly condensed, but determined the diameter as 1.90 . A CCD image by Pravec revealed a magnitude of 13.7 and a coma diameter of 0.50 . He said the tail extended 0.2
in PA 240
. Morris judged the magnitude as 12.5 on both the 19th and 25th, but gave the coma diameter as 1.00 and 1.80 , respectively. Another observation by Morris on September 26 revealed a magnitude of 12.4 and a slightly condensed coma 1.40 across. The most prolific visual observers in October were Modic and Bouma. Modic saw the comet on seven nights spanning the 6th to the 25th. His magnitude estimates varied from 12.8 to 13.3, with the brightest occurring around mid-month. He also noted the comet appeared moderately condensed around mid-month and slightly condensed during the other nights, with a diameter of about 0.60 on the 6th and 0.80 on the 25th. Modic noted a stellar condensation of magnitude 14.5 on the 11th. Bouma saw the comet on six nights spanning the 9th to the 19th. He indicated that the magnitude generally brightened from 13.0 to 12.5 during this period. He described the coma as slightly condensed with a diameter of 0.8–1.20 . A CCD image by Pravec on the 19th revealed a magnitude of 12.7, a small well-condensed coma 1.40 across, and a tail extending more than 150 toward PA 232
. Scotti obtained CCD images on the 24th, which revealed a magnitude of 11.0 and 678

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a nuclear magnitude of 17.0. He said the coma was 1.150 across, while the tail extended about 11.40 in PA 234
. The comet reached a maximum elongation of 173
on October 13. The last visual observations of this apparition were made in November, with observers noting little or no condensation within the coma. Morrison and Modic saw the comet on the 9th, giving the magnitude as 13.3 and 13.7, respectively. The coma diameter was given as 1.00 by Morrison and 0.550 by Modic. Modic again determined the magnitude as 13.7 on the 10th, while the coma diameter was 0.700 . Bouma judged the magnitude as 13.0 on the 12th and the coma diameter as 1.00 . Morrison gave the magnitude as 13.5 on the 13th and the coma diameter as 0.60 . The final visual observation was made by Bouma on the 17th. He determined the magnitude as 13.2 and the coma diameter as 0.80 . Nakamura determined the CCD magnitude as 13.3 on November 18. He said the coma was 1.00 across. The comet was still followed via photography and CCD imaging in December, although few observers provided descriptions. E. Jung (Marl, Germany) detected the comet with his 20-cm reflector and determined CCD magnitudes of 14.2–14.3 on the 7th and 15.1 on the 11th. T. Kojima (Chiyoda, Gunma, Japan) acquired two CCD images using his 25-cm reflector on the 9th. He judged the magnitude as 14.2. Nakamura obtained CCD images on the 12th and 15th, giving magnitudes of 14.4 and 14.2, respectively. On the first night, he said the coma was 0.80 across, while the tail extended toward PA 230
. On the second night, he said the coma was 0.90 across. Astronomers at Kiso Observatory (Nagano, Japan) acquired CCD images on December 15, using the 105-cm Schmidt telescope. The nuclear magnitude was determined as 15.4–15.5. Observations decreased in 1994 January as the comet faded. Kojima gave the magnitude as 15.0 on both the 1st and 8th. Scotti and Nakamura both detected the comet on the 5th. Scotti determined the magnitude as 15.3–15.4 and the nuclear magnitude as 19.2, while Nakamura gave the magnitude as 15.3. Nakamura added that the coma was 0.50 across, while the tail extended toward PA 65
. Jung determined the magnitude as 14.6–14.8 on the 8th. Nakamura judged the magnitude as 15.7 on the 9th, noting a coma 0.350 across and a tail extending toward PA 65
. Jung determined the magnitude as 15.5–16.0 on the 14th and 15.1–15.9 on the 17th. On January 30, Kojima estimated the magnitude as 16.5. On February 2, Nakamura determined the magnitude as 15.8, noting a coma 0.60 across and a tail extending toward PA 65
. Kojima gave the magnitude as 16.1 on the 7th. On the 10th, Scotti determined the magnitude as 16.3 and the nuclear magnitude as 20.2. He reported that the coma was 4800 across, while the tail extended 11.40 in PA 238
. Scotti also noted a “sunward spike” that extended 5700 in PA 61
. Kojima estimated the magnitude as 16.5 on February 14. The comet was moving into twilight in March and Nakamura reported the only observations. On the 2nd, he determined the magnitude as 16.3 679

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and the coma diameter as 0.350 . On the 30th, he determined the magnitude as 17.9 and the coma diameter as 0.250 . The comet reached a minimum elongation of 9
on June 8. Only a few observations were reported during the remainder of 1994. Nakamura acquired three CCD images on October 14, giving the magnitude as 19.9 and the coma diameter as 0.20 . Another image on November 8 revealed a magnitude of 19.6 and a coma diameter of 0.20 . S. M. Larson (Catalina Station, Mt. Bigelow, Arizona, USA) acquired three CCD images on December 1, using the 154-cm reflector, and determined the magnitude as 19.7–19.8. Nakamura obtained two images on December 5 and gave the magnitude as 19.4. He added that the coma was 0.20 across, while the tail extended toward PA 295
. Additional images by Nakamura on the 27th revealed a magnitude of 18.9 and a coma diameter of 0.250 . Larson and his colleague, C. W. Hergenrother, acquired four CCD images on December 31, giving the magnitude as 19.5–20.2. Only two sets of observations were reported in 1995. The comet was well placed for observations early in the year, as it reached a maximum elongation of 164
on January 9. Larson (Kitt Peak National Observatory, Arizona, USA) acquired three CCD images on January 28, using the 229-cm reflector. He determined the magnitude as 20.1–20.2. The comet attained its most northerly declination of +38
on January 17. Larson and Hergenrother (Catalina Station) acquired two CCD images on April 2 using the 154-cm reflector. The determined the magnitude as 20.8–21.2. The comet spent most the latter part of the year in twilight, as it passed just 8
from the Sun on August 1. After having moved southward since mid-January, the comet attained a declination of +20
on November 28 and then began a northward motion. The only set of observations made in 1996 came from Larson and Hergenrother (Kitt Peak National Observatory). They obtained three CCD images using the 229-cm reflector and gave the magnitude as 21.3–21.7. The comet reached a maximum elongation of 170
on February 13 and a minimum elongation of 4
on August 30. After having moved northward since last November, the comet attained a declination of +23
on March 18 and then moved southward until reaching a declination of +5
on 1997 January 5. The comet was last detected during 1997 February 1.42–1.44, when Hergenrother and W. Brown (Fred Lawrence Whipple Observatory, Mt. Hopkins, Arizona, USA) acquired three CCD images using the 122-cm reflector. They determined the magnitude as 21.5–22.0. The position on the last image was α = 11h 45.8m, δ = +5
480 (2000). The comet passed aphelion on April 11. Multiple apparition orbits have been calculated by K. Muraoka (1997), Nakano (1998, 2006), P. Rocher (2000, 2001, 2002, 2010), and K. Kinoshita (2003, 2008, 2013). All of these calculations included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of July 14.05 and a period of 7.49 years. The nongravitational terms for 680

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everyone except Rocher (2010) were within the following ranges: A1 = 0.01 to +0.12 and A2 = 0.0046 to 0.0035. Rocher (2010) included the relativity effect of the Sun and determined the nongravitational terms of A1 = +0.16 and A2 = 0.0230. The orbit of Nakano (2006) is given below. T ω Ω (2000.0) i q e 1993 Jul. 14.0531 (TT) 348.6894 2.6655 12.5009 2.316287 0.394905

absolute magnitude: H0 = 5, n = 7.2 (Meyer) full moon: Mar. 30, Apr. 28, May 28, Jun. 27, Jul. 26, Aug. 25, Sep. 23, Oct. 23, Nov. 21, Dec. 21, 1992 Jan. 19, Feb. 18, Mar. 18, Apr. 17, May 16, Jun. 15, Jul 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6, Mar. 8, Apr. 6, May 6, Jun. 4, Jul. 3, Aug. 2, Sep. 1, Sep. 30, Oct. 30, Nov. 29. Dec. 28, 1994 Jan. 27, Feb. 26, Mar. 27, Apr. 25, May 25, Jun. 23, Jul. 22, Aug. 21, Sep. 19, Oct. 19, Nov. 18, Dec. 18, 1995 Jan. 16, Feb. 15, Mar. 17, Apr. 15, May 14, Jun. 13, Jul. 12, Aug. 10, Sep. 9, Oct. 8, Nov. 7, Dec. 7, 1996 Jan. 5, Feb. 4, Mar. 5, Apr. 4, May 3, Jun. 1, Jul. 1, Jul. 30, Aug. 28, Sep. 27, Oct. 26, Nov. 25, Dec. 24, 1997 Jan. 23, Feb. 22 sources: G. Forti, AAP, 215 (1989), pp. 382, 384; S. Nakano, Nakano Note, No. 538 (1990 May 2); S. Nakano, MPC, No. 16380 (1990 Jun. 8); A. C. Gilmore, P. M. Kilmartin, M. Lindgren, and G. Tancredi, IAUC, No. 5546 (1992 Jun. 16); R. H. McNaught and D. I. Steel, MPC, No. 22116 (1993 Jun. 4); J. V. Scotti, MPC, Nos. 22279, 22286 (1993 Aug. 2); J. V. Scotti, MPC, No. 22440 (1993 Sep. 1); J. V. Scotti, MPC, No. 22521 (1993 Sep. 30); J. V. Scotti, P. Pravec, and C. S. Morris, ICQ, 15 (1993 Oct.), pp. 143–4, 169; T. Kobayashi and P. Pravec, MPC, No. 22611 (1993 Oct. 30); R. J. Modic, A. Hale, P. Pravec, and J. V. Scotti, ICQ, 16 (1994 Jan.), pp. 4, 23; E. Jung, A. Nakamura, and J. V. Scotti, MPC, Nos. 22985–6 (1994 Feb. 26); [Kiso] and A. Nakamura, MPC, No. 23153 (1994 Mar. 27); W. C. Morrison, R. J. Bouma, A. Nakamura, C. S. Morris, and J. V. Scotti, ICQ, 16 (1994 Apr,), pp. 34, 68; E. Jung and A. Nakamura, MPC, No. 23260 (1994 Apr. 25); A. Nakamura, MPC, No. 24253 (1994 Dec. 18); A. Nakamura, ICQ, 17 (1995 Jan.), p. 38; S. M. Larson and A. Nakamura, MPC, No. 24428 (1995 Jan. 16); T. Kojima, S. M. Larson, and C. W. Hergenrother, MPC, No. 24604 (1995 Feb. 15); T. Kojima, MPC, No. 24783 (1995 Mar. 17); A. Nakamura, ICQ, 17 (1995 Apr.), p. 77; T. Kojima, MPC, No. 24935 (1995 Apr. 15); S. M. Larson and C. W. Hergenrother, MPC, No. 25098 (1995 May 14); S. M. Larson and C. W. Hergenrother, MPC, No. 26610 (1996 Mar. 5); K. Muraoka correspondence with G. W. Kronk (1997); C. W. Hergenrother and W. Brown, MPC, No. 29174 (1997 Mar. 24); S. Nakano, Nakano Note, No. 664 (1998 Apr. 26); P. Rocher correspondence with G. W. Kronk (2000, 2001, 2002, 2010); J. Licandro, G. Tancredi, M. Lindgren, H. Rickman, and R. G. Hutton, Icarus, 147 (2000 Sep.), pp. 165, 175; K. Kinoshita correspondence with G. W. Kronk (2003, 2008, 2013); S. Nakano, Nakano Note, No. 1308 (2006 Apr. 7); P. M. Kilmartin correspondence with G. W. Kronk (2011). 681

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107P/Wilson– Recovered: 1992 June 11.42 (Δ = 0.68 AU, r = 1.36 AU, Elong. = 105
) Harrington Last seen: 1993 January 26.3 (Δ = 1.14 AU, r = 2.07 AU, Elong. = 154
) Closest to the Earth: 1992 July 20 (0.4692 AU) Calculated path: AQR (Rec), PSC (Jun. 19), ARI (Jul. 19), TAU (Aug. 4), GEM (Sep. 4), CNC (Oct. 21), GEM (Dec. 6) Although this comet was recovered as minor planet 4015, this was the apparition that led to the discovery that it was identical to periodic comet Wilson–Harrington, which had been lost since 1949. This “minor planet” was recovered on a single image obtained with the 208-cm reflector at McDonald Observatory (Fort Davis, Texas) on 1992 June 11.42. The position was α = 22h 29.3m, δ = 7
340 (2000). It was casually followed during the next few weeks. CCD images were acquired by R. E. McCrosky and C.-Y. Shao (Oak Ridge Observatory, Massachusetts, USA) on June 29, July 26, and August 2 while using the 155-cm reflector. S. J. Bus (Lowell Observatory, Anderson Mesa Station, Arizona, USA) used the 183-cm reflector to acquired CCD images on August 3 and 4, giving the CCD magnitude as 17.1. M. W. Buie and H. Picken (Lowell Observatory) obtained two CCD images on August 8 using the 107-cm reflector. B. G. Marsden made an announcement on an International Astronomical Union Circular issued on August 13 that E. L. G. Bowell and B. A. Skiff (Lowell Observatory) had found images of this object on plates exposed during the Palomar Sky Survey in 1949 and that a faint, slightly fan-shaped tail was then present. Marsden then noted that the 1949 object was actually periodic comet Wilson-Harrington, thus establishing that the lost comet had been rediscovered. It was also stated that Bowell had examined the CCD images that had been acquired by Buie and Picken on August 8. He determined the B magnitude as 18.4 and the R magnitude as 17.7. He said no coma was present. Bowell wrote, “Taken together, the observations suggest that the object is a largely inactive comet that undergoes occasional outburst.” During the remainder of August and all of September, the comet was only observed at two observatories. McCrosky and Shao obtained CCD images at Oak Ridge Observatory on August 24, September 25, and September 30, but provided no physical descriptions. T. Seki (Geisei, Kochi, Japan) acquired an image on August 29, using his 60-cm reflector, and estimated the magnitude as 18.5. The comet reached a minimum elongation of 72
on August 28, at which time it also attained its most northerly declination of +28
. Following the announcement that this “minor planet” was actually periodic comet Wilson–Harrington, Bowell pointed out that “if cometary activity occurs at an orbital longitude similar to that in 1949, it is to be expected around the beginning of Oct. 1992.” This led to an increase in observations starting in October. D. G. Schleicher (Lowell Observatory) acquired CCD spectrographs of the comet on October 4, 6, and 7, using the 183-cm reflector. A total of 682

cometography: a catalog of comets

11 exposures were obtained, with each exposure being 20 minutes in length. The magnitude was given as 17.8. A. Nakamura (Kuma Kogen Astronomical Observatory, Ehime, Japan) obtained three CCD images with a 60-cm reflector on October 25 and determined the magnitude as 18.2. J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired three CCD images on November 30, using the 91-cm reflector, and determined the magnitude as 18.1. McCrosky and Shao were the most prolific astronomers during the last three months of the year, acquiring 12 images from October 23 to December 24. None of these images revealed a trace of coma or tail. After having moved southward since late August, the comet attained a declination of +20
on November 30 and then began a northward motion. The comet reached a maximum elongation of 179
on 1993 January 6. The final astrometric position was obtained by astronomers at McDonald Observatory on January 20.23, using the 208-cm reflector. The position was α = 6h 50.1m, δ = +21
100 (2000). No physical description was provided. The comet was last detected on January 26.3, when S. M. Larson (Catalina Station, Mt. Bigelow, Arizona, USA) acquired CCD images with the 154-cm reflector to aid in determining “the rotational characteristics of the comet as well as to search for any detectable coma.” No position or physical characteristics were provided. A. B. Chamberlin, L.-A. McFadden, R. Schulz, Schleicher, and Bus (1996) examined the images obtained with the 183-cm reflector at Lowell Observatory in August and October. They were specifically looking for cyanogen, “which is the most easily observed volatile species in comets.” No trace was found. Multiple apparition orbits have been calculated by B. G. Marsden (1992), S. Nakano (1998, 2002, 2006, 2011, 2015), G. V. Williams (1999), and K. Kinoshita (2003). All of these calculations included full planetary perturbations. The result was a perihelion date of 1992 August 21.74 and a period of 4.29 years. The orbit of Nakano (2015) is given below. T ω Ω (2000.0) i q e 1992 Aug. 21.7396 (TT) 90.8707 271.0641 2.7860 0.996390 0.622794

absolute magnitude: H = 16.5, G = 0.15, asteroidal (Meyer) full moon: May 16, Jun. 15, Jul 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6 sources: E. L. G. Bowell, B. A. Skiff, and B. G. Marsden, IAUC, No. 5585 (1992 Aug. 13); E. L. G. Bowell, M. W. Buie, and H. Picken, IAUC, No. 5586 (1992 Aug. 13); R. E. McCrosky and C.-Y. Shao, MPC, No. 20595 (1992 Aug. 13); T. Seki, H. Picken, R. E. McCrosky, C.-Y. Shao, and B. G. Marsden, MPC, Nos. 20685, 20743, 20752, 20783 (1992 Sep. 12); R. E. McCrosky and C.-Y. Shao, MPC, No. 21063 (1992 Nov. 10); J. V. Scotti, R. E. McCrosky, and C.-Y. Shao, MPC, Nos. 21221, 21226 (1992 Dec. 9); R. E. McCrosky and C.-Y. Shao, MPC, No. 21395 (1993 Feb. 6); S. M. Larson, Bulletin of the American 683

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Astronomical Society, 25 (1993 Jun.), p. 1057; A. Nakamura and [McDonald], MPC, Nos. 22292, 22358 (1993 Aug. 2); A. B. Chamberlin, L.-A. McFadden, R. Schulz, D. G. Schleicher, and S. J. Bus, Icarus, 119 (1996 Jan.), pp. 173–81; S. Nakano, Nakano Note, No. 672 (1998 Apr. 29); G. V. Williams, CCO, 13th ed. (1999), pp. 78–9; S. Nakano, Nakano Note, No. 848 (2002 May 7); K. Kinoshita correspondence with G. W. Kronk (2003); S. Nakano, Nakano Note, No. 1326 (2006 Apr. 12); S. Nakano, Nakano Note, No. 2134 (2011 Oct. 29); S. Nakano, Nakano Note, No. 2860 (2015 Apr. 2). C/1992 N1 Discovered: 1992 July 2.46 (Δ = 1.54 AU, r = 0.83 AU, Elong. = 30
) (Machholz) Last seen: 1992 July 30.81 (Δ = 1.63 AU, r = 0.90 AU, Elong. = 30
) Closest to the Earth: 1992 June 15 (1.5201 AU) 1992 XVII=1992k Calculated path: PER (Disc), AUR (Jul. 3), TAU (Jul. 13), GEM (Jul. 20), ORI (Jul. 22), GEM (Jul. 25) D. E. Machholz (Colfax, California, USA) discovered this comet on 1992 July 2.46. He was using 27  120 binoculars and estimated the magnitude as 9. The comet was described as a diffuse coma, 30 across, with condensation. The position was α = 4h 43.7m, δ = +36
520 (2000). Machholz had spent 61 hours searching for comets since his discovery of C/1992 F1. A. Hale (Las Cruces, New Mexico, USA) was the first to confirm the comet, when he located it with his 41-cm reflector on July 3.45 in poor seeing. He estimated the magnitude as 9.2 and said the comet was diffuse, with condensation. Machholz saw the comet with his 15-cm reflector on July 3.47. He again estimated the magnitude as 9. At the time of discovery, the comet was already a couple of weeks passed its closest distance from Earth, while perihelion was still over eight days away. In addition, the elongation from the Sun was 30
and decreasing, which made it very difficult for observatories to follow the comet. Subsequently, only four observatories managed to acquire images and precise positions in the course of only five days. The first came on July 5, when E. F. Helin, K. J. Lawrence, L. Lee, and D. Moraru (Palomar Observatory, California, USA) exposed two films using the 46-cm Schmidt telescope. They estimated the magnitude as 9. Two images were acquired by E. Meyer, E. Obermair, and H. Raab (Linz, Austria) on the 9th, using the 29-cm reflector, but no physical descriptions were provided. Also on the 9th, T. Seki (Geisei, Kochi, Japan) photographed the comet using his 60-cm reflector, estimating the magnitude as 10 and describing the comet as diffuse, with a condensation. S. Ueda (Kushiro, Hokkaido, Japan) and Seki independently photographed the comet on the 10th. They both estimated the magnitude as 10. Seki measured the last position on July 10.79, giving it as α = 5h 21.1m, δ = +30
480 (2000). A few visual observers continued to follow the comet in July. Machholz gave the magnitude as 9.0 on the 5th, using an 11-cm reflector. He indicated

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the comet as slightly condensed and 2.00 across. C. S. Morris (near Mt. Wilson, California, USA) and Machholz independently saw the comet on the 6th. Morris was using his 26-cm reflector, noting the magnitude as 9.2 and describing the coma as well condensed and 1.80 across. Using a 15-cm reflector, Machholz determined the magnitude as 9.1. He reported a slightly condensed coma 2.00 across. Machholz judged the magnitude as 8.7 on the 7th and said the comet’s appearance was unchanged from the previous night. Hale and Machholz independently saw the comet on the 8th. Hale gave the magnitude as 9.2. Machholz saw the comet with a 27  120 monocular. He determined the magnitude as 9.0, noting a moderately condensed coma 30 across. No observations were reported for nearly three weeks, despite attempts by several visual observers. The comet reached a minimum elongation of 28
on July 16. D. A. J. Seargent (The Entrance, New South Wales, Australia) made an “uncertain observation” with his 25  100 binoculars on the 28th, estimating the magnitude as 10. Using the same instrument, he made an observation on the 29th that was “very marginal, apparent confirmation of previous observation.” He again estimated the magnitude as 10. The comet was last detected on July 30.81, when Seargent again saw the comet using 25  100 binoculars. He noted, “marginal under prevailing conditions; may have been slightly enhanced by Swan-band filter.” Seargent determined the magnitude as 9.8. Machholz and Hale looked for the comet from July 31 to August 25, but no trace was found. The first orbit was calculated by S. Nakano and was published on 1992 July 11. This used five precise positions from July 5–10 and determined the perihelion date as 1992 July 11.06. The only additional orbit was calculated by Nakano and was published on 1993 January 9. This used eight positions from July 5–10. The result was a perihelion date of 1992 July 10.82. This orbit is given below. T 1992 Jul. 10.8186 (TT)

ω 162.6392

Ω (2000.0) 235.1287

i 57.6407

q 0.819198

e 1.0

absolute magnitude: H10 = 8.8 (Meyer) full moon: Jun. 15, Jul 14, Aug. 13 sources: A. Hale, ICQ, 14 (1992 Jul.), p. 79; D. E. Machholz and A. Hale, IAUC, No. 5553 (1992 Jul. 3); E. F. Helin, K. J. Lawrence, L. Lee, D. Moraru, and C. S. Morris, IAUC, No. 5557 (1992 Jul. 6); D. E. Machholz, IAUC, No. 5560 (1992 Jul. 8); S. Nakano and T. Seki, IAUC, No. 5562 (1992 Jul. 11); E. F. Helin, K. J. Lawrence, L. Lee, D. Moraru, T. Seki, and S. Ueda, MPC, No. 20546 (1992 Aug. 13); D. E. Machholz, D. A. J. Seargent, and A. Hale, ICQ, 14 (1992 Oct.), pp. 104, 117; E. Meyer, E. Obermair, and H. Raab, MPC, No. 20862 (1992 Oct. 11); S. Nakano, Nakano Note, No. 581 (1993 Jan. 9); D. E. Machholz correspondence with G. W. Kronk (2011).

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84P/Giclas Recovered: 1992 June 30.78 (Δ = 1.97 AU, r = 1.96 AU, Elong. = 75
) Last seen: 1993 March 20.45 (Δ = 2.41 AU, r = 2.43 AU, Elong. = 80
) 1992 XXV=1992l Closest to the Earth: 1992 November 11 (0.9584 AU) Calculated path: PSC (Rec), CET (Jul. 12), TAU (Aug. 20) Two predictions were provided for the return of this comet. S. Nakano (1988, 1989) took 81 positions from 1978–1986 and included perturbations by all nine planets. He predicted that the comet would next arrive at perihelion on 1992 September 13.09. S. W. Milbourn (1991) took 89 positions from 1978–1986 and included full planetary perturbations. He determined the next perihelion date as September 13.10. This comet was recovered by T. Seki (Geisei, Kochi, Japan) on 1992 June 30.78, when he photographed the comet’s predicted position using the 60-cm reflector. He described the comet as very diffuse, with a central condensation, and estimated the magnitude as 18. The position was α = 1h 41.2m, δ = +3
370 (2000). Seki obtained confirming photographs during July 7.76–7.77 and July 9.78. He continued to describe the comet as very diffuse, estimating the magnitude as 18 on the first date and 18.5 on the second date. The only observers during the next two months were R. E. McCrosky and C.-Y. Shao (Oak Ridge Observatory, Massachusetts, USA). They used the 155-cm reflector and a CCD camera to acquire six images from July 28 to August 24, but no physical descriptions were provided. A few physical descriptions were provided in September. A. Nakamura (Kuma Kogen Astronomical Observatory, Ehime, Japan) obtained a CCD image on September 25, using a 60-cm reflector, and estimated the magnitude as 15.9. He noted that the coma was 0.20 across, while a tail extended toward PA 260
. J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired three CCD images on September 28, using the 91-cm reflector, and determined the nuclear magnitude as 19.7. After having moved northward since its recovery, the comet attained a declination of +10
on September 17 and then began a southward motion. The first visual observation was made by R. J. Bouma (Netherlands) on October 1. He used a 45-cm reflector and judged the magnitude as 14.1. Bouma added that the coma appeared completely uncondensed and 0.80 across. T. Kojima (Chiyoda, Gunma, Japan) obtained two CCD images on October 30, using his 25-cm reflector. He gave the magnitude as 15.5. After having moved southward since mid-September, the comet attained a declination of +9
on October 31 and then began a northward motion. Although the comet was moving away from the Sun, it was closest to Earth around the middle of November and seemed to show some brightening. Nakamura estimated the magnitude as 15.7 on the 2nd, adding that the coma was 0.250 across. In the course of the Palomar Planet-Crossing Asteroid Survey, E. F. Helin (Palomar Observatory, California, USA) and her team accidentally found this comet on film 686

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exposed with the 46-cm Schmidt telescope on the 19th. They gave the magnitude as 15.0. Two CCD images by Kojima on the 23rd revealed a magnitude of 15.5. Nakamura obtained images on the 24th and 30th, giving the magnitude as 15.2 and 15.5, respectively. He also judged the coma diameter as 0.35–0.40 . Nakamura also visually observed the comet using the 60-cm reflector. He determined the magnitude as 14.9 and said the coma was 0.50 across. The comet reached a maximum elongation of 169
on November 25. On December 1, Scotti obtained three CCD images, giving the magnitude as 15.0 and the nuclear magnitude as 19.0. He said the coma was 3500 across, while the tail extended more than 2.50 , curving from PA 297
to PA 267
. CCD images were obtained by Nakamura on the 17th and 25th, providing magnitudes of 15.5 and 14.1, respectively. On the first night, he said the coma was 0.30 across, while the tail extended toward PA 350
. On the second night, the coma appeared 0.50 across, while the tail extended toward PA 55
. Kojima estimated the magnitude as 16 on the 22nd. On the 29th, H. Mikuz (Ljubljana, Slovenia) obtained an image using his 20-cm reflector and gave the magnitude as 14.3. He noted a strong condensation and said the coma was 1.50 across. Nakamura made visual observations on three nights. He judged the magnitude as 14.8 on both the 2nd and 17th, and 13.7 on the 25th. The coma was 0.50 across on the first two nights, and 0.60 across with a moderate condensation on the last night. Only a few observations were reported during the first two months of 1993. Scotti obtained three CCD images on January 1, giving the magnitude as 15.3 and the nuclear magnitude as 19.1. He reported a “complex coma and tail structure.” The coma was asymmetric toward PA 99
. A sharp tail curved from PA 76
to PA 65
at 1.030 from the nuclear condensation. There was also a “fainter, residual structure” extending 1.730 in PA 60
and a fainter tail-like structure extending 1.400 in PA 256
. Mikuz determined the magnitude as 16.0 on the 18th and reported a slightly condensed coma 0.50 across. Nakamura gave the magnitude as 16.2 on the 21st, while the coma was 0.350 across. On January 25, Scotti acquired CCD images which revealed a magnitude of 16.5–16.6 and a nuclear magnitude of 20.6. He said the coma was 2900 across. Scotti noted two tails, one extending 1.2200 in PA 76
and the other extending 1.730 in PA 257
. Nakamura next saw the comet on February 14. He gave the magnitude as 17.0 and said the coma was 0.20 across. The comet was last detected during March 20.44–20.45, when Nakamura acquired two CCD images using a 60-cm reflector. He determined the magnitude as 17.6 and said the coma was 0.20 across. The position on the last image was α = 5h 14.6m, δ = +21
500 (2000). Multiple apparition orbits have been calculated by P. Rocher (1995, 2000, 2006, 2007), B. G. Marsden (1996), Nakano (1996, 2003, 2010), and K. Kinoshita (2000, 2001, 2006, 2013). All of these calculations included full planetary perturbations, while only those published from 1996 onward solved for nongravitational effects. The result was a perihelion date of 687

cometography: a catalog of comets

September 13.09 and a period of 6.96 years. Nakano (1996) used positions from 1931–1993 and determined nongravitational terms of A1 = +0.02 and A2 = +0.0042. Kinoshita (2000, 2001) used positions from 1931–2000 and determined nongravitational terms within the following ranges: A1 = 0.29 to 0.27, A2 = 0.0009, and A3 = +0.11 to +0.12. Nakano (2003) used positions from 1931–2000 and determined nongravitational terms of A1 = +0.02 and A2 = 0.0005. For the calculations published from 2006 onward, the nongravitational terms were within the following ranges: A1 = 0.26 to 0.01 and A2 = 0.0023 to 0.0021. The orbit of Nakano (2010) is given below. T ω Ω (2000.0) i q e 1992 Sep. 13.0923 (TT) 276.4852 112.5263 7.2833 1.846786 0.493214

absolute magnitude: H10 = 11.5 (Meyer) full moon: Jun. 15, Jul 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6, Mar. 8, Apr. 6 sources: S. Nakano, Nakano Note, No. 526 (1988 Nov. 1); S. Nakano, MPC, No. 14594 (1989 May 20); S. W. Milbourn, HBAA for 1992 (1991), p. 73; T. Seki, IAUC, No. 5561 (1992 Jul. 10); T. Seki, R. E. McCrosky, and C.-Y. Shao, MPC, Nos. 20546–7 (1992 Aug. 13); R. E. McCrosky, and C.-Y. Shao, MPC, No. 20672 (1992 Sep. 12); T. Kojima and E. F. Helin, MPC, Nos. 21159, 21165 (1992 Dec. 9); A. Nakamura, IAUC, No. 5680 (1992 Dec. 21); H. Mikuz, ICQ, 15 (1993 Jan.), p. 32; T. Kojima and J. V. Scotti, MPC, Nos. 21305–6, 21316 (1993 Feb. 6); J. V. Scotti, MPC, Nos. 21632, 21637 (1993 Mar. 8); A. Nakamura, ICQ, 15 (1993 Apr.), p. 78; A. Nakamura, ICQ, 15 (1993 Jul.), p. 127; A. Nakamura, MPC, Nos. 22279–80 (1993 Aug. 2); R. J. Bouma, ICQ, 16 (1994 Apr.), p. 69; P. Rocher correspondence with G. W. Kronk (1995, 2000, 2006, 2007); B. G. Marsden, CCO, 11th ed. (1996), pp. 66–7; S. Nakano, Nakano Note, No. 639 (1996 Apr. 15); K. Kinoshita correspondence with G. W. Kronk (2000, 2001, 2006, 2013); S. Nakano, Nakano Note, No. 937 (2003 Apr. 20); S. Nakano, Nakano Note, No. 1911 (2010 Apr. 9). 14P/Wolf Recovered: 1992 July 10.75 (Δ = 2.25 AU, r = 2.45 AU, Elong. = 89
) Last seen: 1993 January 25.13 (Δ = 2.62 AU, r = 2.64 AU, Elong. = 80
) 1992 Closest to the Earth: 1992 October 10 (1.4513 AU) XXII=1992m Calculated path: AND (Rec), PSC (Jul. 19), CET (Nov. 12) A prediction for the return of this comet was calculated by S. Nakano (1989). He took 50 positions from 1950–1984 and included full planetary perturbations. Nakano then integrated the comet’s motion to this apparition and predicted a perihelion date of 1992 August 28.13. This comet was recovered by T. Seki (Geisei, Kochi, Japan) on 1992 July 10.75, when he photographed the predicted position using the 60-cm reflector. He described the comet as “nearly stellar with a faint coma” 688

cometography: a catalog of comets

and estimated the magnitude as 19.5–20. The position was α = 0h 48.3m, δ = +22
160 (2000). Seki obtained another photograph on July 25.72, but the seeing was bad and there was only a hint of a smudge of magnitude 20 at the position of the comet. Additional photographs were made by Seki on July 26.69 and July 26.72, which officially confirmed the recovery. The magnitude was again estimated as 20. Very few observations were obtained during the remainder of 1992. D. D. Balam (Dominion Astrophysical Observatory, Saanich, British Columbia, Canada) acquired three CCD images on July 27, using the 183-cm reflector, but provided no physical description. The comet attained its most northerly declination of +23
on August 1. J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired three CCD images on September 25, using the 91-cm reflector, giving the magnitude as 17.7 and the nuclear magnitude as 20.7. He reported a coma 1200 in diameter and a tail extending 0.730 in PA 258
. Balam again acquired CCD images of the comet on September 27, but provided no physical description. The comet reached a maximum elongation of 178
on October 14. A. Nakamura (Kuma Kogen Astronomical Observatory, Ehime, Japan) obtained two CCD images on November 2, using the 60-cm reflector, and estimated the magnitude as 17.5. He added that the coma was 0.150 across. Three more CCD images by Scotti on December 2 revealed a magnitude of 18.9–19.2. The comet attained its most southerly declination of 2
on December 29. The comet was last detected during 1993 January 25.12–25.13, when Scotti acquired three CCD images using the 91-cm reflector. He determined the magnitude as 20.4–20.7. The position on the last date was α = 1h 51.7m, δ = 1
080 (2000). Multiple apparition orbits have been calculated by Nakano (1997, 2006, 2014), K. Kinoshita (1998, 2000, 2003, 2008), and P. Rocher (1999, 2000, 2001, 2004). All of these calculations included full planetary perturbations. The result was a perihelion date of August 28.13 and a period of 8.25 years. The orbit of Nakano (2014) is given below. T ω Ω (2000.0) i q e 1992 Aug. 28.1336 (TT) 162.2859 204.1452 27.4777 2.427700 0.405601

absolute magnitude: H0 = 9.5, n = 8 (Meyer) full moon: Jun. 15, Jul 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6 sources: S. Nakano, Nakano Note, No. 532 (1989 May 5); S. Nakano, MPC, No. 14594 (1989 May 20); T. Seki, IAUC, No. 5567 (1992 Jul. 27); T. Seki, MPC, No. 20546 (1992 Aug. 13); D. D. Balam, MPC, No. 20672 (1992 Sep. 12); J. V. Scotti, MPC, Nos. 20862, 20865 (1992 Oct. 11); D. D. Balam, MPC, No. 20963 (1992 Nov. 10); J. V. Scotti, MPC, No. 21306 (1993 Feb. 6); A. Nakamura, ICQ, 15 (1993 Apr.), p. 77; A. Nakamura, MPC, No. 22280 (1993 Aug. 2); S. Nakano, Nakano Note, No. 660 (1997 May 4); K. Kinoshita 689

cometography: a catalog of comets

correspondence with G. W. Kronk (1998, 2000, 2003, 2008); P. Rocher correspondence with G. W. Kronk (1999, 2000, 2001, 2004); S. Nakano, Nakano Note, No. 1309 (2006 Apr. 7); S. Nakano, Nakano Note, No. 2736 (2014 Jun. 25). 106P/1992 O1 Recovered: 1992 July 28.74 (Δ = 1.69 AU, r = 1.60 AU, Elong. = 67
) (Schuster) Last seen: 1992 December 18.97 (Δ = 1.04 AU, r = 1.87 AU, Elong. = 136
) Closest to the Earth: 1992 December 10 (1.0310 AU) 1992 Calculated path: TAU (Rec), ORI (Sep. 8), TAU (Sep. 10), GEM (Sep. 12), LYN XXIV=1992n (Oct. 26), UMa (Dec. 9) This comet was missed at its 1985 apparition. S. Nakano (1979) had taken 32 positions from the discovery apparition of 1977–1978 and had included perturbations by all nine planets. He then integrated the motion to 1985 and predicted the comet would next pass perihelion on 1985 June 2.34. The comet was not expected to exceed magnitude 18 and was lost in twilight for several months when at its brightest. In preparation for the comet’s return in 1992, Nakano (1987, 1989) redetermined the orbit from the discovery apparition by using 36 positions and including full planetary perturbations. He then integrated the comet’s motion to 1992 and predicted it would next pass perihelion on September 6.39. The comet was recovered during 1992 July 28.74–28.76 and July 29.77–29.78, when T. Seki (Geisei, Kochi, Japan) obtained photographs using his 60-cm reflector. He estimated the magnitude as 18 on both nights. Seki described the comet as “small and diffuse without nucleus” and noted a faint tail extending toward PA 245
. The position on the first image was α = 3h 55.6m, δ = +10
560 (2000). The next observations were two CCD images obtained by R. E. McCrosky and C.-Y. Shao (Oak Ridge Observatory, Massachusetts, USA) on August 25. No physical descriptions were provided. Even though there were plenty of astrometric positions provided during the remainder of 1992, only a few observers reported descriptions. A. Nakamura (Kuma Kogen Astronomical Observatory, Ehime, Japan) obtained two CCD images on September 25, using the 60-cm reflector, and gave the magnitude as 16.1. J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired two CCD images on October 22, using the 91-cm reflector, giving the magnitude as 18.2. Nakamura obtained pairs of CCD images on October 25, November 24, and November 30, providing magnitudes of 16.6, 17.2, and 17.3, respectively. Scotti acquired three CCD images on December 1, giving the magnitude as 17.1 and the nuclear magnitude as 21.0. He reported a coma diameter of 1900 and said the tail extended more than 100 in PA 278
. The comet was last detected during December 18.96–18.97, when V. S. Casulli (Colleverde di Guidonia, Italy) acquired two CCD images using a 690

cometography: a catalog of comets

31-cm reflector. He estimated the magnitude as 16.0. The position on the last date was α = 8h 51.4m, δ = +49
210 (2000). Multiple apparition orbits have been calculated by Nakano (1992, 1996, 2004, 2011, 2014), P. Rocher (1994, 2000, 2007), B. G. Marsden (2001), and K. Kinoshita (2001, 2007, 2014). All of these calculations included full planetary perturbations, while only those published from 2001 onward solved for nongravitational effects. The result was a perihelion date of September 6.42 and a period of 7.26 years. The nongravitational terms were within the following ranges: A1 = +0.01 to +0.15 and A2 = +0.0061 to +0.0086. The orbit of Nakano (2011) is given below. T ω Ω (2000.0) i q e 1992 Sep. 6.4168 (TT) 355.7312 50.6018 20.1338 1.539235 0.589521

absolute magnitude: H0 = 13, n = 6 (Meyer) full moon: Jul. 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8 sources: S. Nakano, Nakano Note, No. 370 (1979 Nov. 29); S. Nakano, Nakano Note, No. 508 (1987 Aug. 20); S. Nakano, MPC, No. 14594 (1989 May 20); T. Seki, IAUC, No. 5570 (1992 Jul. 30); T. Seki and S. Nakano, MPC, Nos. 20547, 20602 (1992 Aug. 13); R. E. McCrosky and C.-Y. Shao, MPC, No. 20672 (1992 Sep. 12); J. V. Scotti, MPC, No. 20963 (1992 Nov. 10); J. V. Scotti, MPC, Nos. 21159, 21165 (1992 Dec. 9); V. S. Casulli, MPC, No. 21306 (1993 Feb. 6); A. Nakamura, MPC, No. 22280 (1993 Aug. 2); P. Rocher correspondence with G. W. Kronk (1994, 2000, 2007); S. Nakano, Nakano Note, No. 644 (1996 Apr. 11); B. G. Marsden, CCO, 14th ed. (2001), pp. 92–3; K. Kinoshita correspondence with G. W. Kronk (2001, 2007, 2014); S. Nakano, Nakano Note, No. 1043 (2004 Apr. 6); S. Nakano, Nakano Note, No. 2149 (2011 Nov. 2); S. Nakano, Nakano Note, No. 2758 (2014 Aug. 25). 33P/Daniel Recovered: 1992 July 29.79 (Δ = 2.29 AU, r = 1.68 AU, Elong. = 42
) Last seen: 1993 May 28.16 (Δ = 2.62 AU, r = 2.87 AU, Elong. = 94
) 1992 Closest to the Earth: 1993 February 2 (1.3917 AU) XXIII=1992o Calculated path: TAU (Rec), ORI (Aug. 2), GEM (Aug. 6), CNC (Sep. 15), LEO (Oct. 13), LMi (Nov. 10), LEO (Nov. 24), UMa (Dec. 26), COM (1993 Jan. 3), CVn (Jan. 26), UMa (Feb. 14), LEO (May 18) S. Nakano (1988, 1989, 1991) published a prediction for this comet’s return, which used 18 positions from 1964–1986, full planetary perturbations, and solved for nongravitational effects. He gave the perihelion date as 1992 September 1.67. The comet was recovered by T. Seki (Geisei, Kochi, Japan) on a photograph obtained with his 60-cm reflector on 1992 July 29.79. He estimated the magnitude as 19 and noted the comet appeared diffuse and condensed. The position was α = 5h 38.6m, δ = +21
140 (2000). Seki confirmed the recovery on photographs obtained with the same telescope on August 8.79 691

cometography: a catalog of comets

and August 9.79. The appearance was unchanged, except that the magnitude was estimated as 18. The next observations of this comet were not made until September 29, when J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) acquired three CCD images using the 91-cm reflector. He noted an asymmetric coma measuring 13400 by 9300 , with a magnitude of 16.3 and a nuclear magnitude of 20.1. Only a few physical descriptions were provided during the remainder of the year. A. Nakamura (Kuma Kogen Astronomical Observatory, Ehime, Japan) acquired three CCD images of the comet on October 25, using the 60-cm reflector. He gave the magnitude as 16.0. Nakamura gave the magnitude as 16.4 on November 30. Scotti obtained three images on December 2, giving the magnitude as 16.6–16.7 and the nuclear magnitude as 20.7. He noted an asymmetric coma measuring 2600 by 3500 and a tail that extended 0.840 in PA 282
. After having moved northward since its recovery, the comet attained a declination of +26.3
on October 6. It then moved southward until attaining a declination of +26.0
on November 10. The only observers to follow the comet during 1993 were Nakamura and Scotti. Nakamura gave the magnitude as 16.9 on January 21. On January 24, Scotti gave the magnitude as 17.2–17.3 and the nuclear magnitude as 20.6. He noted an asymmetric, fan-shaped coma extending 0.50 to 0.90 between PA 138
and PA 290
. Nakamura gave the magnitude as 16.8 on February 19. The comet attained its most northerly declination of +38
on March 10. Scotti gave the nuclear magnitude as 22.3 on March 30. On April 22, Scotti gave the magnitude as 19.7 and the nuclear magnitude as 22.3. The comet reached a maximum elongation of 146
on March 2. The comet was last detected on May 28.16, when Scotti obtained two CCD images using the 91-cm reflector. The image was described as diffuse and uncondensed, with a diameter of 1600 and a magnitude of 20.7. The position on the last date was α = 11h 23.1m, δ = +26
150 (2000). Multiple apparition orbits have been calculated by Nakano (1997, 2001, 2005), B. G. Marsden (2001), and K. Kinoshita (2003, 2009). These calculations included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of September 1.67 and a period of 7.06 years. Although Kinoshita (2009) gave the nongravitational terms as A1 = +0.12 and A2 = +0.0504, the other calculations revealed nongravitational terms within the following ranges: A1 = +0.24 to +0.31 and A2 = +0.0723 to +0.0745. Marsden’s orbit is given below. T ω Ω (2000.0) i q e 1992 Sep. 1.6718 (TT) 11.0064 69.0545 20.1360 1.649447 0.551965

absolute magnitude: H0 = 13.2, n = 4.2 (Meyer) full moon: Jul. 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6, Mar. 8, Apr. 6, May 6, Jun. 4 692

cometography: a catalog of comets

sources: S. Nakano, Nakano Note, No. 525 (1988 Nov. 1); S. Nakano, MPC, No. 14594 (1989 May 20); S. Nakano, HBAA for 1992 (1991), p. 73; T. Seki, IAUC, No. 5581 (1992 Aug. 10); T. Seki, MPC, No. 20672 (1992 Sep. 12); J. V. Scotti, MPC, Nos. 20863, 20865 (1992 Oct. 11); J. V. Scotti, MPC, Nos. 21306, 21316 (1993 Feb. 6); J. V. Scotti, MPC, Nos. 21632, 21637 (1993 Mar. 8); J. V. Scotti, MPC, No. 21982 (1993 May 6); J. V. Scotti, MPC, No. 22116 (1993 Jun. 4); A. Nakamura and J. V. Scotti, MPC, Nos. 22280, 22286 (1993 Aug. 2); S. Nakano, Nakano Note, No. 656 (1997 May 3); B. G. Marsden, CCO, 14th ed. (2001), pp. 78–9; S. Nakano, Nakano Note, No. 770 (2001 Mar. 3); S. Nakano, Nakano Note, No. 1204 (2005 Jul. 4); K. Kinoshita correspondence with G. W. Kronk (2003, 2009). 154P/1992 Q1 Discovered: 1992 August 28.41 (Δ = 2.28 AU, r = 1.83 AU, Elong. = 52
) (Brewington) Last seen: 1993 March 30.19 (Δ = 3.76 AU, r = 3.26 AU, Elong. = 112
) Closest to the Earth: 1993 January 3 (1.8021 AU) 1992 XIV=1992p Calculated path: AUR (Disc), LYN (Sep. 3), LMi (Oct. 31), LEO (Nov. 1), LMi (Dec. 12), LYN (Jan. 10), CNC (Feb. 17) H. J. Brewington (Cloudcroft, New Mexico, USA) discovered this comet using his 41-cm reflector and a Swan-band filter on 1992 August 28.41. He had began sweeping for comets at 2:30 a.m. (local time) and found the comet at 3:50 a.m. Brewington had spent a total of 99 hours searching for comets since his discovery of C/1991 Y1. The comet’s magnitude was estimated as 10 and it was described as “very small and diffuse.” Brewington gave the position as α = 7h 15m, δ = +36.5
(2000). The first confirmations were made by A. Sugie (Dynic Astronomical Observatory, Shiga, Japan) and T. Kojima (Chiyoda, Gunma, Japan). Sugie acquired three images during August 28.74–28.76 using his 25-cm Schmidt telescope. He estimated the magnitude as 13 and noted the comet was “very faint and diffuse.” Kojima acquired an image on August 28.76 using his 25-cm reflector and estimated the magnitude as 13.5. Kojima said the comet’s appearance on the image was “weak” and it was only detected following Sugie’s identification. A few observations were made during the remainder of August. T. Seki (Geisei, Kochi, Japan) acquired three images of the comet on the 29th using his 60-cm reflector. He estimated the magnitude as 14 and said a tail extended 50 in PA 300
. Seki reported that a visual observation revealed a magnitude of 11.3 and a coma 3.50 across. Three CCD images were obtained by P. Pravec (Ondřejov Observatory, Czech Republic) on the 31st while using an 18-cm reflector. He said the comet appeared “prolonged in PA 300
.” C. S. Morris (Pine Mountain Club, California, USA) visually observed the comet with his 26-cm reflector on the 30th. He estimated the magnitude as 11.5 and noted the coma was slightly condensed and 2.20 across. The comet was seen by A. Hale (Alamogordo, New Mexico, USA) and R. J. Bouma (Netherlands) on the 31st. Hale observed with his 41-cm 693

cometography: a catalog of comets

reflector and estimated the magnitude as 11.5. Bouma was using his 25-cm reflector. He determined the magnitude as 12.1 and said the coma was uncondensed and 1.70 across. The comet was well observed by visual observers in September, with the majority noting only slight condensation within the coma. Hale and A. Nakamura (Kuma, Ehime, Japan) saw it on the 1st. Hale determined the magnitude as 10.8. Nakamura was using his 20-cm reflector and judged the magnitude as 10.4, adding that the coma was 2.80 across. H. Mikuz (Ljubljana, Slovenia) and R. J. Modic (Ohio, USA) were the most prolific observers during the remainder of the month. Mikuz visually spotted the comet on five nights spanning the 3rd to the 8th using his 20-cm reflector. He indicated that the comet faded from magnitude 10.9 to 11.2, while the coma varied from about 2.5–40 . Mikuz switched to a CCD camera on the 26th, which was attached to a 19-cm flat-field camera. He determined the magnitude as 13.2. Mikuz added that the coma was 3.50 across, while a tail extended about 50 in PA 300
. Modic saw the comet on five nights spanning the 4th to the 28th, using a 36-cm reflector. He indicated that the magnitude faded from 11.4 to 12.8, while the coma varied from 1.1–2.00 . Modic reported a stellar central condensation on the 4th, estimating its magnitude as 13.5. On the 5th, he reported an “almost stellar” central condensation of magnitude 13.9. Modic’s observation on the 24th revealed that the coma was elongated 0.7–0.80 in about PA 300
. With the comet fading, the final visual observations were made in October. Observers continued to describe the coma as slightly condensed. Hale and Nakamura saw the comet on the 1st, giving the magnitude as 12.8 and 12.3, respectively. Nakamura said the coma was 2.20 across. Modic saw the comet on five nights spanning the 2nd to the 8th. He indicated that the magnitude faded from 13.1 to 14.0, while the coma diameter varied from 0.8–1.00 . Modic switched to his 40-cm reflector on the 28th. He judged the magnitude as 14.1 and said the coma was 1.00 across. Nakamura (Kuma Kogen Astronomical Observatory, Ehime, Japan) visually observed the comet with the 60-cm reflector on the 6th. He said the magnitude was 13.4, while the coma diameter was 1.20 . Mikuz acquired a CCD image on the 9th, which revealed a magnitude of 14.4. He said the coma appeared moderately condensed and about 2.50 across, while a tail extended about 50 toward PA 295
. Few observations were reported in November and December, and even fewer physical descriptions. W. Hasubick (Germany) photographed the comet on November 23, using a 140-mm lens. He estimated the magnitude as 13.5 and said the coma was 3.40 wide, and exhibited a tail to the southwest. From the precise positions that were reported on this date, B. G. Marsden was able to confirm that this was periodic comet Swift–Tuttle, giving the perihelion date as 1992 December 12.39 and the period as 135.29 years. 703

cometography: a catalog of comets

The refinement of the orbit enabled two prediscovery images to be located. The first was found on a photographic plate exposed by R. Haver (Cima Ekar Observatory, Italy) with the 40-cm Schmidt telescope during 1992 January 3.08–3.09. Haver said the comet’s appearance was “very weak” and stellar in appearance. He estimated the magnitude as 17.5. The second was found by L. Kohoutek (Calar Alto Observatory, Almería, Spain) using the 80-cm Schmidt telescope on 1992 January 7.09. He estimated the magnitude as 18 and said the comet was “Close to plate limit.” The comet reached a maximum elongation of 148
on January 26 and a minimum elongation of 31
on July 11. The comet was well observed during the remainder of September, with observers reporting only slight condensation. G. Comello (Netherlands) and R. J. Bouma (Groningen, Netherlands) saw the comet on the 28th, 29th, and 30th. Comello was using his 20-cm reflector, giving the magnitude as 9.2 on the first two nights and 9.1 on the last night. The coma was 3–40 across. Bouma was using his 25-cm reflector. He said the magnitude was 9.1 on the first night and 9.0 on the last two nights. In addition, he said the coma was 3.5–3.70 across. Nearly 800 observations were reported to the International Comet Quarterly for October. Observers generally noted that the coma was very slightly condensed at the beginning of the month and was moderately condensed at month’s end. The first person to visually detect the tail was J. Jahn (Germany). He was using his 20-cm reflector on the 10th and stated that the tail extended about 0.20
in PA 270
. Among the most prolific observers were E. P. Bus (Netherlands) and M. Möller (Germany). Bus saw the comet on 16 nights, spanning the 3rd to the 31st. His 11-cm reflector revealed that the comet brightened from 8.7 to 5.8, while the coma diameter generally increased from about 60 to 100 . Bus first detected the tail on the 12th, describing it as 0.1
long in PA 360
. By the 29th, he said the tail extended 0.2
in PA 30
. Möller produced a fine series of observations with his 15-cm reflector from the 1st to the 29th, which indicated a magnitude increase from 9.4 to 6.0 and a coma diameter increase from 40 to 90 . He first detected the gas tail on the 17th, noting that it extended 0.3
in PA 20
. By the 29th, he said it was extending 0.5
in PA 30
. Möller first detected the dust tail on the 20th, noting that it was fan-shaped and extended 0.2
in PA 25
to PA 60
. Möller described the coma as elliptical on the 3rd and elongated on the 4th. Observers with larger telescopes reported a stellar nucleus on several occasions during the month, with J. E. Bortle (Stormville, New York, USA) giving the magnitude as 13.5 on the 6th, as seen in his 32-cm reflector. Structure was also observed within the coma beginning around the middle of the month. As an example, Bortle noted on the 17th, “a vague, dense knot of bright material occupies the coma’s center – but when viewed with 167, one sees a 13th-mag stellar nucleus at the apex of a fanlike mass or diffuse jet sector (the sector is centered at p.a. 220
and is roughly 35
–45
wide in p.a. and extends 1.10 from the nucleus in a 704

cometography: a catalog of comets

sunward direction).” The first naked-eye observation was made by S. Garro (France) on the 31st. He gave the magnitude as 5.9. The comet attained its most northerly declination of +59
on October 2 and reached a maximum elongation of 67
on October 20. The comet was most observed in November, with about 1300 observations being reported to the International Comet Quarterly. In general, most observers reported that the coma was moderately condensed at the beginning of the month and strongly condensed at the end. Two of most prolific observers were Möller and Morris. Möller indicated that the magnitude generally brightened from 5.5 on the 3rd to 4.7 on the 30th, while the coma diameter decreased from 100 to 60 . Although a variety of instruments were used, Möller provided a wonderful series observations of the tail on 13 nights using 10  50 binoculars. The tail length varied from 0.5
to 1.5
during the first half of the month and 1.2
to 2.2
during the second half, while the PA rotated from 35
on the 3rd, to 65
on the 24th, and then 55
on the 30th. Morris said the comet generally brightened from 5.9 to 4.9 from the 1st to the 28th. Using 10  50 binoculars, he said the tail extended 4
in PA 46
on the 14th and 3.75
in PA 30
on the 28th. Numerous observers were reporting naked-eye observations during the last ten days of the month. H. Mikuz (Ljubljana, Slovenia) acquired several CCD images on November 23. These were 10-minute exposures and revealed a straight ion tail extending 6.7
in PA 44
and a fan-shaped dust tail extending about 2
toward PA 10
to PA 40
. Mikuz added that the ion tail contained clouds and knots of material along its length. Although the comet was still well observed in December, with about 500 reported observations, the comet’s elongation from the Sun was decreasing, causing it to drop deeper into evening twilight. Subsequently, the number of observations steadily declined as the month progressed. Most observers reported a moderate to strongly condensed coma. Bortle used 10  50 binoculars on the 3rd to estimate the comet’s magnitude at 5.2 and its coma diameter as 50 . On the 7th, he gave a magnitude estimate of 5.4. Bouma judged the magnitude as 5.0 on the 12th, noting that the tail extended 2.5
in PA 45
. The magnitude was estimated as 5.0 by Hale on the 15th, when a tail of 1.8
was noted in PA 58
. Also on the 15th, Bortle determined a magnitude of 5.3 and said the tail extended 1.0
in PA 53
. Hale again saw the comet on the 17th, giving a magnitude estimate of 5.0 and tracing the tail for 2.0
in PA 50
. He noted that the comet was then “just barely visible to the naked eye.” On the 20th, Bortle used his 10  50 binoculars to estimate the magnitude at 5.2 and the coma diameter at 3.50 . Switching to 20  120 binoculars, this observer traced the tail for 1.1
in PA 57
. Few observations were made after December 26, as the comet was moving into twilight. The last observation that was made before the comet was lost in the Sun’s glare came from T. Kato (Kyoto, Kyoto, Japan) on 1993 January 1, when he estimated the magnitude as 6.3 using 7  50 binoculars. 705

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It should be noted that during the months of November and December, the comet displayed remarkable structure within the inner regions of the coma, closely resembling the features reported during its previous return in 1862. Structures described as “envelopes” or “hoods,” together with “fountain” and “jet” features, were reported by most observers who examined the inner coma region using telescopes of 25-cm aperture or greater and were well shown in CCD images obtained by D. Cardoen and D. Zambenedetti (Puimichel Observatory, France) with the 106-cm reflector on six nights from November 29 to December 20. Similar features were also observed visually by Bortle from late October until mid-December using 32-cm and 50-cm reflectors. Bortle writes that “P/Swift–Tuttle has been the ONLY comet for which jet structure was clearly evident since comet Bennett in 1970, in my opinion.” D. McDavid and D. C. Boice (Limber Observatory, Texas, USA) obtained several CCD images with the 40-cm reflector during November 25–30. After measuring the “position angles of elliptical regions of the inner coma,” they determined rotation periods of 63.0, 66.9, 69.7, 68.1, and 68.6 hours, giving an average period of 67.3 +/ 2.6 hours. The comet reached a minimum elongation of 12
on 1993 January 17. It remained lost in twilight until February 17, when G. W. Wolf (New Zealand) and A. F. A. L. Jones (Nelson, New Zealand) independently spotted the comet in the morning sky. Wolf was using a 21-cm reflector and saw the comet when it was about 4
above the south-southeastern horizon. He gave the magnitude as 8.8–8.9 and noted a slightly condensed coma 2.2–2.40 across. Jones located the comet with his 32-cm reflector when it was about 13
above the horizon and in weak twilight. He determined the magnitude as 9.1 and noted a completely diffuse coma that was 10 across. The comet could now only be followed by observers in the Southern Hemisphere, but it was also fading, so that only 33 additional visual observations were reported during the next month and a half. The two most prolific observers were Jones and P. Camilleri (Cobram, Victoria, Australia). Jones saw the comet on 11 nights spanning February 18 to April 1, mostly using his 32-cm reflector. He indicated that the magnitude faded from 9.4 to 11.2, while the coma showed little or no condensation and had a diameter of 1–30 . Camilleri saw the comet on six nights spanning February 23 to April 1, initially using 20  80 binoculars, but switching to his 20-cm reflector in late March. He indicated the magnitude faded from 9.5 to 11.1, while the comet was completely diffuse and 2–50 across. The observations by Jones and Camilleri on April 1 were the last visual observations of this apparition. During this same period, A. C. Gilmore (Mt. John University Observatory, Lake Tekapo, New Zealand) acquired images of the comet using a 60-cm reflector. Although these were primarily for astrometric purposes, he did give the nuclear magnitude as 16.3 on March 22. A photograph was obtained by astronomers at Perth Observatory (Bickley, Western Australia, Australia) on April 19 and two CCD images 706

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were obtained at Siding Spring Observatory (New South Wales, Australia) on May 11. No descriptive information was provided. The comet attained its most southerly declination of 71
on May 15. During the period of 1993 June 30 and 1994 April 1, the comet was exclusively followed by astronomers at Siding Spring Observatory; however, no physical descriptions were reported. During this same period the comet reached a maximum elongation of 93
on 1993 June 3, a minimum elongation of 54
on 1993 October 22, and a maximum elongation of 109
on 1994 April 4. After moving northward since 1993 May, the comet attained a declination of 56
on 1993 September 1 and then moved southward until reaching a declination of 70
on 1994 February 3. During the remainder of 1994, CCD images were obtained at La Silla Observatory (Chile) and Siding Spring Observatory. The images acquired at La Silla were obtained on April 9 and April 14, using the 220-cm reflector. The nuclear magnitude was determined as 19.6 on both nights. Astronomers at Siding Spring Observatory obtained two CCD images on May 2, but provided no physical descriptions. After having moved northward since early February, the comet attained a declination of 46
on August 16 and then began a southerly motion. The comet reached a minimum elongation of 51
on September 26. As 1995 began, the comet was moving southward; however, after attaining a declination of 55
on January 29, it began a northward motion. The comet reached a maximum elongation of 119
on March 20. Astronomers at Siding Spring Observatory obtained their final CCD images of the comet on March 29. The final astrometric positions of this comet were obtained during 1995 April 1.20–1.29, April 2.21–2.23, and April 5.23–5.24, when astronomers at the La Silla Observatory acquired CCD images with the 220-cm reflector. They noted the nuclear magnitude faded from 21.3 to 21.5 during this period. The position on the last image was α = 9h 23.3m, δ = 50
310 (2000). The final observation of this comet was obtained by K. J. Meech, O. R. Hainaut, and J. M. Bauer (Mauna Kea, Hawaii, USA) on 1997 December 30.55, when they acquired CCD images using the 996-cm Keck II reflector and the Low Resolution Imaging Spectrometer. The magnitude was determined as 23.3 and there was no trace of coma. The inferred nucleus radius was 13.73 kilometers. The comet’s predicted position was α = 10h 01.8m, δ = 39
460 (2000). H. Böhnhardt and K. Birkle (1994) published the results of an analysis of CCD images that had been obtained from 1992 October 28 to November 27. The images were acquired with the 123-cm reflector and a variety of filters at Calar Alto Observatory (Almería, Spain). They detected “dust and gas jets from three sources on the nucleus, a dust fan close to the Sun direction, brightness excess areas which partly coincided with the [cyanogen] gas jets in the coma, and dust and ion tail streamers partly superimposed on other 707

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coma features.” They also determined the rotation period of the nucleus as 2.795 days. Using CCD photometry when the comet was located 5.3 AU from the Sun following perihelion, D. P. O’Ceallaigh, A. Fitzsimmons, and I. P. Williams (1995) deduced a mean effective radius of the nucleus as 11.8 kilometers, assuming an albedo of 14%, and an upper mass estimate of 7  1018 g. Only 3% of the nucleus surface area was found to be active. A similar value for the nucleus diameter was obtained as the result of a study by H. Böhnhardt, K. Birkle, and M. Osterloh (1996) of CCD images obtained during April 1994 with the 220-cm reflector at La Silla Observatory. The comet then appeared as a stellar nucleus devoid of coma. From photometric studies by these authors, “assuming an albedo of 0.04 as per 1P/Halley,” a radius of 11 kilometers was estimated “for two rotation phase angles differing by about 75
.” The authors concluded “that the nucleus is either of rather spherical shape or that the viewing geometry was almost pole-on during our observations.” Multiple apparition orbits have been calculated by Marsden, G. V. Williams, G. W. Kronk, and G. Waddington (1993), P. Rocher (1995, 2000, 2003), K. Kinoshita (1998), and S. Nakano (1999). All of these included full planetary perturbations, while a few also attempted solving for nongravitational effects. The result was a perihelion date of December 12.32–12.33 and a period of 134.64–135.01 years. All three of Rocher’s orbits have solved for nongravitational effects within the following ranges: A1 = +1.39 to +1.43 and A2 = 0.3346 to 0.1891. Nakano determined nongravitational terms of A1 = +0.32 and A2 = 0.0006. The orbit of Marsden, Williams, Kronk, and Waddington is given below. From orbital computations of Waddington and Marsden, Kronk confirmed the suspicion that the comet of 68 was an earlier return of 109P, the perihelion date occurring on 68 August 27 or 28. He also identified the comet of 188 with 109P, having a perihelion date within the range 188 July 5 to August 2, with July 15 being the most likely. The returns between 188 and 1737 were found to have been unfavorable, explaining the lack of observations at intervening apparitions. T ω Ω (2000.0) i q e 1992 Dec. 12.3241 (TT) 153.0014 139.4444 113.4265 0.958220 0.963589

absolute magnitude: H0 = 4.08, n = 7.78 (A. H. Scholten, 2001) full moon: Dec. 21, 1992 Jan. 19, Feb. 18, Mar. 18, Apr. 17, May 16, Jun. 15, Jul 14, Aug. 13, Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6, Mar. 8, Apr. 6, May 6, Jun. 4, Jul. 3, Aug. 2, Sep. 1, Sep. 30, Oct. 30, Nov. 29. Dec. 28, 1994 Jan. 27, Feb. 26, Mar. 27, Apr. 25, May 25, Jun. 23, Jul. 22, Aug. 21, Sep. 19, Oct. 19, Nov. 18, Dec. 18, 1995 Jan. 16, Feb. 15, Mar. 17, Apr. 15

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sources: G. V. Schiaparelli, MNRAS, 27 (1867 Feb.), p. 134; F. Hayn, AN, 123 (1889 Nov. 2), p. 112; W. T. Lynn, The Observatory, 25 (1902 Aug.), pp. 304–5; B. G. Marsden, AJ, 78 (1973 Sep.), pp. 654–8; H. Kosai, T. Kiuchi, J. B. Tatum, J. V. Scotti, and B. G. Marsden, IAUC, No. 5620 (1992 Sep. 27); D. E. Machholz, C. S. Morris, and A. Hale, IAUC, No. 5621 (1992 Sep. 27); A. Hale, ICQ, 14 (1992 Oct.), pp. 104, 123; T. Seki and J. V. Scotti, MPC, No. 20864 (1992 Oct. 11); B. G. Marsden, CCO, 8th ed. (1993), pp. 37, 70; H. Mikuz, G. Comello, E. P. Bus, M. Möller, J. Jahn, C. S. Morris, J. E. Bortle, and H. Mikuz, ICQ, 15 (1993 Jan.), pp. 5–9, 37–53; J. E. Bortle, S. Garro, A. Hale, T. Kato, G. W. Wolf, and A. F. A. L. Jones, ICQ, 15 (1993 Apr.), pp. 65–7, 88; A. C. Gilmore and [Siding Spring], MPC, No. 22116 (1993 Jun. 4); [Siding Spring], MPC, No. 22280 (1993 Aug. 2); [Siding Spring], MPC, No. 22440 (1993 Sep. 1); B. G. Marsden, G. V. Williams, G. W. Kronk, G. Waddington, Icarus, 105 (1993 Oct.), pp. 420–6; P. Camilleri, ICQ, 15 (1993 Oct.), p. 179; [Siding Spring], MPC, No. 22988 (1994 Feb. 26); R. J. Bouma, ICQ, 16 (1994 Apr.), pp. 73–4; [Perth] and [Siding Spring], MPC, No. 23365 (1994 May 25); [Siding Spring], MPC, No. 23553 (1994 Jun. 23); E. P. Bus, D. Cardoen, and D. Zambenedetti, ICQ, 16 (1994 Oct.), pp. 138–40; P. Rocher correspondence with G. W. Kronk (1995, 2000, 2003); D. P. O’Ceallaigh, A. Fitzsimmons, and I. P. Williams, AAP, 297 (1995 May) pp. L17–L20; [Siding Spring], MPC, No. 25099 (1995 May 14); H. Böhnhardt and K. Birkle, AAP Supplement, 107 (1994 Oct. 1), pp. 101–120; D. McDavid and D. C. Boice, Bulletin of the American Astronomical Society, 27 (1995 Dec.), p. 1338; H. Böhnhardt, K. Birkle, and M. Osterloh, EM&P, 73 (1996 Apr.), pp. 51–8; K. Kinoshita correspondence with G. W. Kronk (1998); S. Nakano, Nakano Note, No. 723 (1999 Nov. 18); K. J. Meech correspondence with G. W. Kronk (2000); A. H. Scholten, Dutch Comet Section Publication, No. 6 (2001 Feb.), p. 13; [European Southern Observatory], MPC, No. 48372 (2003 May 1); K. J. Meech, O. R. Hainaut, and B. G. Marsden, Icarus, 170 (2004 Aug.), pp. 463–76; G. W. Kronk, Meteor Showers. New York: Springer (2014), pp. 195–6. 40P/Väisälä 1 Recovered: 1992 September 26.47 (Δ = 2.99 AU, r = 2.71 AU, Elong. = 65
) Last seen: 1993 September 5.45 (Δ = 2.59 AU, r = 2.20 AU, Elong. = 57
) 1993 VIII=1992u Closest to the Earth: 1993 March 2 (0.9177 AU) Calculated path: CNC (Rec), LEO (Nov. 25), COM (1993 Jun. 17), VIR (Jun. 21) Predictions for the return of this comet were published by G. Forti (1989) and S. Nakano (1990). Forti used 45 positions from 1959–1982, included perturbations by all nine planets, and solved for nongravitational effects. He determined the likely perihelion date as 1993 April 29.16. Nakano used 101 positions from 1939–1982, included full planetary perturbations, and solved for nongravitational effects. He gave the likely perihelion date as April 29.18.

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The comet was recovered during 1992 September 26.47–26.50 and September 27.47–27.49, when J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA) obtained CCD images using the 91-cm reflector. He described the comet as stellar on each night, with a magnitude of 21.7 on the 26th and 21.6 on the 27th. The position on the first image was α = 8h 00.6m, δ = +14
170 (2000). The only other observations reported in 1992 were from December, but most of these were purely for astrometric purposes. The only descriptions were provided by Scotti, when three CCD images on the 2nd revealed a magnitude of 18.0 and a nuclear magnitude of 20.6. He added that the tail extended 0.670 in PA 286
. After having moved southward since its recovery, the comet attained a declination of +10
on December 16 and then began a northward motion. The comet showed signs of brightening in 1993 January, as it continued approaching both the Sun and the Earth. Both N. Kawasato (Uenohara, Yamanashi, Japan) and T. Seki (Geisei, Kochi, Japan) detected the comet on the 2nd. Kawasato was using a 30-cm reflector and a CCD camera, while Seki took photographs with his 60-cm reflector. Both astronomers estimated the magnitude as 17. Seki added that the tail extended 20 in PA 300
. A. Nakamura (Kuma Kogen Astronomical Observatory, Ehime, Japan) acquired two CCD images on the 21st, using a 60-cm reflector. He determined the magnitude as 15.2 and said the tail extended 0.30 in PA 295
. A few minutes later, Nakamura visually spotted the comet using the same telescope. He then judged the magnitude as 15.0 and the coma diameter as 0.30 . Scotti obtained three CCD images on the 24th, giving the magnitude as 14.9 and the nuclear magnitude as 18.1. He added that the coma was 2700 across, while the tail extended 5.030 in PA 283
. On January 29, T. Kojima (Chiyoda, Gunma, Japan) photographed the comet with his 25-cm reflector. He estimated the magnitude as 15.5. Three observers reported visual observations of the comet in February. The comet also reached a maximum elongation of 176
on the 12th. Nakamura determined the magnitude as 13.2 on both the 14th and 19th, noting a moderately condensed coma. He said the coma’s diameter was 0.40 on the first night and 0.70 on the second night. A. Hale (Las Cruces, New Mexico, USA) saw the comet with his 41-cm reflector on the 21st and 22nd. He said the comet’s appearance was the same on both nights, with a magnitude of 13.1 and a coma that was moderately condensed and about 10 across. The magnitude was given as 13.0 by Nakamura on the 25th. He added that the coma was moderately condensed and 0.80 across. R. J. Modic (Ohio, USA) observed the comet with his 40-cm reflector on the 27th. He judged the magnitude as 13.5 and noted a slightly condensed coma 0.30 across. A few more observers were able to follow the comet in March. Hale and Nakamura each saw the comet on three nights and indicated that it was moderately condensed. Hale gave the magnitude as 13.1 on the 3rd, 12.9 on the 17th, and 13.2 on the 25th. Also on the 17th, he wrote, “there seems to be 710

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a weak [condensation] slightly off-center toward the W side of the coma.” Nakamura judged the magnitude as 13.1 on the 13th, 13.1 on the 21st, and 13.4 on the 22nd. He gave coma diameters of 0.6–0.70 during this period. C. S. Morris (Pine Mountain Club, California, USA) saw the comet with his 26-cm reflector on the 13th and determined the magnitude as 12.5. He reported a slightly condensed coma 0.80 across. R. J. Bouma (Netherlands) gave the magnitude as 13.9, as seen in his 25-cm reflector. He noted a very slightly condensed coma 0.50 across. H. Mikuz (Ljubljana, Slovenia) acquired a CCD image of the comet on the 18th using his 20-cm reflector and reported a fanlike tail extending about 2.50 in PA 135–170
. Three CCD images were obtained by Scotti on March 30. He determined the magnitude as 14.0 and the nuclear magnitude as 18.1. Scotti added that the coma was 3800 in diameter and exhibited a tail extending 2.270 toward PA 136
. The comet showed signs of fading in April. Nakamura made three visual observations with the 60-cm reflector, giving the magnitude as 13.8 on the 14th, 13.8 on the 19th, and 14.0 on the 25th. He indicated a coma diameter of 0.6–0.80 . Nakamura also acquired CCD images on these dates, noting a tail extending toward PA 130–135
. Hale judged the magnitude as 13.4 on the 12th and 13.3 on the 24th. For the 12th, he wrote, “the comet is more vague and diffuse than during previous observations.” For the 24th, Hale wrote, “comet larger and more diffuse than during previous observations.” Morris determined the magnitude as 13.2 and noted a slightly condensed coma 1.40 across. Bouma gave the magnitude as 14.0 on the 19th and 14.1 on the 20th. He reported that the coma showed little condensation and was 0.60 across on both nights. Mikuz acquired three CCD images during the month, noting a strongly condensed coma 0.50 across on each night. He described the tail as fanlike on the 8th and said it extended 2.50 toward PA 125
. On the 17th, Mikuz reported a fanlike tail extending 2.50 in PA 130
. On the 26th, he said the tail extended 3.50 in PA 130
. The comet attained its most northerly declination of +25
on April 8. The comet was moving away from both the Sun and Earth as May began. The final visual observation was obtained by Modic on the 11th while using his 40-cm reflector. He judged the magnitude as 14.1 and said the coma was slightly condensed and 0.50 across. Nakamura obtained CCD images on the 15th and 20th, giving the magnitude as 14.8 and 14.5, respectively. For the first night, he said the coma was 0.60 across, while the tail extended 2.50 in PA 135
. On the second night, he said the coma was 0.450 across, while the tail extended toward PA 135
. A CCD image by Mikuz on the 17th revealed a magnitude of 14.2, a strongly condensed coma 0.50 across, and a fan-like tail extending 3.50 in about PA 145
. Scotti acquired two CCD images on the 28th. He determined the magnitude as 15.1 and the nuclear magnitude as 19.6. Scotti added that the coma was 2800 across and the tail extended 2.340 in PA 121
. Only a few observations were made in June and July. Nakano (Sumoto, Hyogo, Japan) acquired two CCD images on both the 4th and 11th, giving 711

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the magnitude as 14.5–14.6 and 13.9–14.3, respectively. A CCD image by Mikuz on June 19 revealed a magnitude of 15.0. He added that the comet had a “star-like appearance,” with a coma 0.50 across. Scotti acquired two CCD images on July 22, giving the magnitude as 16.5 and the nuclear magnitude as 21.5. He said the coma was 0.520 across, while the tail extended about 20 in PA 113
. Scotti added that a “faint sunward spike” was visible that extended 1.20 toward PA 286
. Two additional CCD images were obtained by Scotti on July 24. These revealed the magnitude as 16.3 and the nuclear magnitude as 21.3. Scotti noted a coma 0.350 across and a tail extending about 20 in PA 113
. He again noted the faint sunward spike, writing that it extended 1.280 in PA 288
. The comet was last detected on 1993 September 5.45, when Nakamura obtained two CCD images with the 60-cm reflector. He judged the magnitude as 18.0 and said the coma was 0.20 across. The position on the last image was α = 14h 38.7m, δ = 5
330 (2000). Multiple apparition orbits have been calculated by P. Rocher (1995, 2004, 2014), G. V. Williams (1999), Nakano (2001, 2011), and K. Kinoshita (2003, 2004, 2014). These included full planetary perturbations and solved for nongravitational effects. The result was a perihelion date of April 29.17 and a period of 10.78 years. The nongravitational terms were within the following ranges: A1 = +0.02 to +0.12 and A2 = 0.0110 to 0.0099. The orbit of Kinoshita (2014) is given below. T ω Ω (2000.0) i q e 1993 Apr. 29.1721 (TT) 47.3844 135.0772 11.5961 1.783016 0.634716

absolute magnitude: H0 = 9.5, n = 6, weighted towards visual observations (Meyer) full moon: Sep. 12, Oct. 11, Nov. 10, Dec. 9, 1993 Jan. 8, Feb. 6, Mar. 8, Apr. 6, May 6, Jun. 4, Jul. 3, Aug. 2, Sep. 1, Sep. 30 sources: G. Forti, AAP, 215 (1989), pp. 382, 384; S. Nakano, Nakano Note, No. 536 (1990 May 2); S. Nakano, MPC, No. 16379 (1990 Jun. 8); J. V. Scotti, IAUC, No. 5623 (1992 Sep. 28); J. V. Scotti, MPC, Nos. 20864–5 (1992 Oct. 11); A. Nakamura, IAUC, No. 5699 (1993 Jan. 28); J. V. Scotti and T. Seki, MPC, Nos. 21311, 21316 (1993 Feb. 6); N. Kawasato and J. V. Scotti, MPC, Nos. 21632–3, 21637 (1993 Mar. 8); A. Hale, A. Nakamura, and H. Mikuz, ICQ, 15 (1993 Apr.), pp. 67, 100; J. V. Scotti, MPC, No. 21984 (1993 May 6); C. S. Morris, A. Nakamura, and H. Mikuz, IAUC, No. 5788 (1993 May 13); T. Kojima, MPC, No. 22116 (1993 Jun. 4); A. Nakamura, R. J. Modic, and H. Mikuz, ICQ, 15 (1993 Jul.), pp. 135–6; A. Nakamura, J. V. Scotti, and S. Nakano, MPC, Nos. 22280–1, 22286 (1993 Aug. 2); J. V. Scotti, MPC, No. 22440 (1993 Sep. 1); A. Nakamura, MPC, No. 22521 (1993 Sep. 30); C. S. Morris, S. Nakano, and J. V. Scotti, ICQ, 15 (1993 Oct.), pp. 144, 180; A. Nakamura and A. Hale, ICQ, 16 (1994 Jan.), pp. 5, 26; R. J. Bouma, ICQ, 16 (1994 Apr.), p. 76; P. Rocher correspondence with 712

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G. W. Kronk (1995, 2014); G. V. Williams, CCO, 13th ed. (1999), pp. 64–5; S. Nakano, Nakano Note, No. 780 (2001 Apr. 26); K. Kinoshita correspondence with G. W. Kronk (2003, 2004, 2014); S. Nakano, Nakano Note, No. 2158 (2011 Nov. 4). 82P/Gehrels 3 Recovered: 1991 November 8.91 (Δ = 3.10 AU, r = 3.98 AU, Elong. = 148
) Last seen: 1995 July 4.03 (Δ = 3.74 AU, r = 4.09 AU, Elong. = 103
) 1993 XIV=1992v Closest to the Earth: 1994 February 16 (2.5170 AU) Calculated path: PSC (Rec), ARI (1992 Mar. 12), TAU (May 31), ORI (1993 Apr. 28), TAU (May 2), GEM (May 7), CNC (Jul. 29), LEO (Sep. 29), VIR (1994 Aug. 31) Two predictions were published for the return of this comet. S. Nakano (1986) used 40 positions from 1975–1986, while Nakano (1990) used 48 positions from 1975–1987. Both calculations included full planetary perturbations. After integrating the comet’s motion to this apparition, Nakano (1986) predicted the perihelion date as 1993 July 25.43, while Nakano (1990) determined it as July 25.42. This comet was recovered by J. V. Scotti (Steward Observatory, Kitt Peak, Arizona, USA). Using the 91-cm reflector, he acquired two CCD images during 1992 September 26.45–26.46 and three CCD images during September 28.45–28.47. He described the comet as stellar, noting a magnitude of 22.0 on the first image and 21.6 on the last. The position on the first image was α = 5h 25.2m, δ = +23
080 (2000). No further observations were reported during the remainder of 1992. Scotti’s positions confirmed a single-night detection by astronomers at Pic du Midi Observatory (France). They acquired two CCD images on 1991 November 8.91 and November 8.93, using the 201-cm reflector and an R filter. The comet appeared stellar with an R magnitude of 19.5–20.1. After having moved southward since the 1991 November recovery, the comet attained a declination of +6
on 1991 December 9 and then began a northerly motion. It reached a minimum elongation of 0.3
on 1992 May 5 and a maximum elongation of 180
on 1992 December 9. The comet attained its most northerly declination of +23.1
on 1992 October 4. Only two sets of observations were reported in 1993, with both coming from Scotti. On January 22, he gave the magnitude as 20.1 and the nuclear magnitude as 21.7. In addition, he said the coma was 1000 across. The next observations came on December 9, when Scotti acquired three CCD images, revealing a magnitude of 19.3 and a nuclear magnitude of 21.6. He said the coma was 1000 across, while the tail extended