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Past, Present, and Future Orbits by Kazuo Kinoshita

Photos of 186P exposed on 1979 July 18 and 19
Copyright © 1977 by R. D. Eberst

These are copies of the two prediscovery photographs obtained of 186P at Siding Spring Observatory (New South Wales, Australia) during July of 1977. The left-hand image was exposed for one hour and 10 minutes beginning on July 18.58. The right-hand image was exposed for one hour and 20 minutes beginning on July 19.61. North is up, while east is to the left. (Special thanks to Russell Eberst for allowing me to use these images).


G. J. Garradd (Siding Spring Observatory, New South Wales, Australia) discovered this comet on images obtained on 2007 January 25.70, January 25.72, and January 25.73, using the 0.5-m Uppsala Schmidt and a CCD camera. The three images indicated a magnitude of 18.0-18.3. In late February, M. Meyer (Germany) announced that he had found three prediscovery images on Siding Spring Observatory Digital Sky Survey images from 1975 and 1996. He had been slightly adjusting the early orbits that were calculated when he found an image of the comet on a plate exposed on 1996 February 26.64. The magnitude was given as 17.8. The orbit improvement brought about by this position then enabled Meyer to locate the comet on images exposed on 1975 May 31.38 and June 3.39. The magnitude on these images was given as 15.5. In linking all of these positions, G. V. Williams (Central Bureau for Astronomical Telegrams) found that comet images reported on IAU Circular No. 3247 (1978 Jul. 25) by R. D. Eberst also belonged to this comet. The images were also exposed at Siding Spring Observatory, using the 1.2-m UK Schmidt, on 1977 July 18.58 and July 19.61. The magnitude was given as 18, while a tail extended about 3'.

Historical Highlights

  • B. G. Marsden (Central Bureau for Astronomical Telegrams) published the first orbit on January 29. Using 20 positions spanning the period of 2007 January 25 to 29, he calculated a parabolic orbit with a perihelion date of 2006 March 26.53. Marsden published a revised orbit on February 2. Using 25 positions spanning the period of January 25 to 31, he calculated an elliptical orbit with a perihelion date of 2008 March 17.83 and a period of 10.2 years. Following the finding of prediscovery images going back to 1975, Marsden determined the perihelion date as March 20.50 and the period as 10.64 years.
  • Additional Images

    Siding Spring Observatory photograph of 186P exposed on 1996 February 26
    Copyright © 1996 by the Anglo-Australian Observatory Board

    This is the image M. Meyer found of this comet from 1996 February 26. The photograph was obtained at Siding Spring Observtory using the 1.2-m UK Schmidt telescope. It was an 80-minute exposure using IIIaF film and an OG 590 filter. The comet appears as the short tail in the very center of the photograph.