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Past, Present, and Future Orbits by Kazuo Kinoshita

A. Nakamura image of 106P exposed on 1999 October 17
Copyright © 1999 by Akimasa Nakamura (Kuma Kogen Astronomical Observatory, Japan)

The CCD image was taken on 1999 October 17.57 UT, using a 0.60-m f/6 Ritchey-Chretien telescope.


This comet was discovered by H.-E. Schuster (European Southern Observatory) on 1975 October 9.16. It was initially simply reported as a "moving object," but Schuster remarked that "Although the object may be a minor planet, it seems to show some fuzziness to the northeast." The magnitude was given as 17. Schuster and R. M. West said a 40-minute exposure with a 100-cm Schmidt telescope on October 14 showed a tail about 20 arc seconds long, thus confirming this object was a comet.

L. D. Schmadel (Astronomisches Rechen-Institut) submitted accurate positions of 8 minor planets found on European Southern Observatory plates obtained in early September. Brian G. Marsden found that one of these objects, photographed on September 5.20, 6.13, and 7.28, was identical to Schuster's comet. He also pointed out that Schuster was the discoverer of this minor planet. The magnitude was given as 17.5. J. Schubart (Astronomisches Rechen-Institut) announced on October 21 that the September 6 image was somewhat diffuse.

Historical Highlights

  • Following the discovery of the prediscovery images, Marsden computed the first orbit, which revealed Schuster's comet was moving in a short-period orbit. The perihelion date was given as 1978 January 6.7, the perihelion distance was 1.63 AU, and the orbital period was 7.46 years. He added that the comet apparently made a moderately close approach to Jupiter in 1958. Ultimately, the perihelion date was given as January 6.82, the perihelion distance was 1.628 AU, and the orbital period was 7.47 years.
  • A long exposure was obtained with the European Southern Observatory 360-cm telescope on October 16. This showed a fan-shaped tail about one arc minute long extending toward the north-northeast.
  • The total magnitude was estimated as about 16 from late October into early December. Other observers occasionally noted the tail and reported lengths ranging from 15 arc seconds to one arc minute. West reported the comet appeared very diffuse on a image obtained with the 100-cm telescope on 1978 January 8.
  • This comet was recovered by T. Seki (Geisei, Japan) on 1992 July 28.74. He described the comet as "small and diffuse." The magnitude was estimated as 18 and there was no nucleus. A precise position indicated the prediction needed a correction in the perihelion date of +0.04 day. Seki also noted that his July 29 photographs showed a faint tail extending toward PA 245 degrees.
  • The comet was next expected to pass perihelion on 1999 December 16. It was recovered on 1999 September 1.54 by R. H. McNaught (Siding Spring, Australia), while using the 1.0-m f/8 reflector and a CCD camera. The comet brightened to nearly magnitude 12 during the last half of November of 1999, before it began fading. Interestingly, Seiichi Yoshida has analyzed this apparition and found a sudden drop of about a magnitude at the end of November. The Webmaster also notes that the comet became more diffuse after this event.
  • Additional Images

    R. Ligustri image of 106P exposed on 2000 January 23
    Copyright © 2000 by Rolando Ligustri (Italy)

    The CCD image was taken on 2000 January 23, using a 0.20-m f/6.3 Meade Cassegrain. It is a combination of three 120-second exposures. North is up and east is to the left.