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87P/Bus

Past, Present, and Future Orbits by Kazuo Kinoshita

Discovery

     S. J. Bus (California Institute of Technology, Pasadena, USA) discovered this comet on a plate exposed with the 122-cm UK Schmidt telescope by K. S. Russell (Siding Spring Observatory, New South Wales, Australia) on 1981 March 2.58. The plate was obtained as part of a survey of minor planets. Bus indicated a magnitude of 17.5 and described the comet as centrally condensed with a faint tail extending about 20" toward the northwest. A confirmation plate was obtained by Russell on March 3.59.

     Following the calculation of the first orbits, Bus located prediscovery images of this comet on additional Siding Spring plates. The first plate was obtained by Russell on February 9.65 and revealed the comet at magnitude 19.5-20. The second plate was obtained by M. Hartley on February 13.64 and revealed the comet's magnitude as 20.

Historical Highlights

  • B. G. Marsden first calculated a parabolic and an elliptic orbit on March 9, based on the available observations, and remarked that "it is probable that the comet is a short-periodic one." The latter orbit indicated a perihelion on 1981 June 29.94. After the detection of the prediscovery observations Marsden was able to confirm the suspected periodic nature. He calculated a perihelion date of 1981 June 19.97 and a period of 6.57 years. Calculations during the few years by S. Nakano and Marsden revealed the perihelion date as June 11.36-11.47 and the period as 6.52-6.53 years.
  • The comet was poorly observed during the remainder of this apparition. T. Seki (Kochi Observatory, Geisei Station, Japan) gave the magnitude as 18 on March 5, while Bus gave it as 16.5 on March 7. After attaining a magnitude of 16 on plates exposed at Siding Spring around mid-March, the magnitude was given as 18 by A. C. Gilmore and P. M. Kilmartin (Mt. John Observatory, New Zealand) on April 3 and 17.5 by astronomers at Palomar Observatory (California, USA) on April 25. The last four observations were obtained at Agassiz station (Massachusetts, USA) by C.-Y. Shao on May 23 and 24, and on June 6 and 27.
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