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Past, Present, and Future Orbits by Kazuo Kinoshita


     Kesao Takamizawa (Japan) discovered this comet on 1984 July 30.53 in Capricornus. He estimated the magnitude as 10 and said the comet was 2 arc minutes across. The comet was confirmed by K. Saito (Tokyo Observatory, Dodaira Station, Japan) on July 31.68 and C. S. Morris and A. Hale (Whitaker Peak, California, USA) on August 1.41. Saito estimated the magnitude as 10, while Morris and Hale determined it as 9.5 and 9.3, respectively. Morris added that a faint tail extended 4-5 arc minutes toward the west.
     T. Seki (Geisei, Japan) found a prediscovery image on a photographic plate exposed on July 26.68. He estimated the magnitude of the trailed image as 17.
     P. Wild (Zimmerwald, Switzerland) found prediscovery images on plates exposed on July 6.03 and 8.04. Wild said the July 8 had been noticed at the time because of its "bright asymmetric coma and fanshaped tail," but it was rejected as a plate defect when a similar image could not be found on the July 6 plate. An image was found on the July 6 plate after the first orbit had been computed. The image consisted of a "distinct nucleus" of magnitude 17 situated within a "very tenuous coma." The comet's total magnitude was estimated as 16 on the 6th and 13 on the 8th.

Historical Highlights

  • The first orbit was published on August 3. Brian G. Marsden (Central Bureau for Astronomical Telegrams) computed a parabolic orbit using 8 positions obtained during the period of July 31 to August 2. It indicated a perihelion date of 1984 May 5 and a perihelion distance of 1.56 AU. He added, "It is quite probable that the comet is a short-period one." On August 7, International Astronomical Union Circular number 3970 said S. Nakano (Tokyo, Japan) and Marsden had independently confirmed the comet moved in a short-period orbit. Perihelion was expected between May 23 and 26 at a distance of about 1.57 AU. The calculations indicated the orbital period was between 6.49 and 7.23 years. After the prediscovery images were announced, Marsden published a new orbit on August 20, which indicated a perihelion date of 1984 May 24 and an orbital period of 7.26 years.
  • The comet faded after its discovery, having already passed both it perihelion and closest distance from Earth. By the end of August it was near magnitude 10.5 and it was near magnitude 12 by the end of September. The comet was last seen on November 25.
  • The comet was next recovered on 1991 February 17.49 by James V. Scotti (University of Arizona, USA) with the Spacewatch telescope. The total magnitude was then determined as between 19.6 and 19.9. Scotti said there was a tail extending about 30 arc seconds toward PA 285-290 degrees. His precise positions indicated the prediction required a correction of -0.5 day. Although the comet was expected to reach magnitude 16 during July and August, observations by amateur astronomers during August revealed the comet had reached magnitude 14. The comet was kept under observation until September 13.
  • The comet next returned to perihelion on 1998 November 7.97. This was not a favorable apparition, with only 13 observations being made during the period of 1998 March 2 to June 19. The brightest reported magnitude was 18.7.
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