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Past, Present, and Future Orbits by Kazuo Kinoshita


     Jacqueline Ciffreo (Caussols) discovered this comet on 1985 November 8.10 on plates exposed with the 0.9-m Schmidt. She described it as diffuse and estimated the magnitude as 10. She obtained a further image on November 8.11. M. Koishikawa (Sendai Observatory, Ayashi Station) confirmed the discovery on November 8.81 when the comet was located at the edge of a photographic plate obtained using a 300mm lens.

Historical Highlights

  • Observations within the week following the discovery revealed the comet's magnitude was slightly brighter than 12, with a coma about 2.5 arc minutes across and a tail two arc minutes long.
  • Brian G. Marsden (Central Bureau for Astronomical Telegrams) officially announced the comet's discovery on November 12 and gave a parabolic orbit based on two days' observations. This indicated a perihelion date of 1985 October 8, a perihelion distance of 2.05 AU, and an inclination of 20 degrees. By November 18 enough observations had become available to enable Marsden's colleague Daniel W. E. Green to compute an elliptical orbit which indicated a perihelion date of 1985 October 28.0, a perihelion distance of 1.72 AU, and an orbital period of 7.81 years. Later revisions indicated a perihelion date of October 30 and an orbital period of 7.22 years.
  • The comet was next expected to return to perihelion in early 1993. J. V. Scotti (Lunar and Planetary Laboratory, Arizona, USA) was using the Spacewatch telescope at Kitt Peak when he recovered the comet on 1992 September 24. He then noted the coma was 15 arc seconds across, while the tail extended 0.36 arc minute toward the west. From observations on that night, as well as on the 25th, he noted a total magnitude of 18.0 and a nuclear magnitude of 20.6. His precise positions indicated the predicted perihelion date needed a correction of +0.6 day, making it 1993 January 23.06. Following the announcement T. Seki (Geisei, Japan) found images on plates exposed on August 26, September 4 and 5. The comet was followed until 1993 February 26, when Scotti photographed it. He then determined the magnitude as 16.5.
  • The comet was next expected at perihelion on 2000 April 18. It was recovered on 1999 November 10 by astronomers at Mount John Observatory in New Zealand. Although the comet was predicted to reach magnitude 17 during April of 2000, no observations were made during the period of 1999 December through 2000 November. Of the 15 positions submitted by astronomers during this apparition, only three included estimates of the comet's brightness. The brightest reported magnitude was about 19.5. The comet was last seen on 2000 December 22.
  • cometography.com