Copyright © 1999 by Akimasa Nakamura (Kuma Kogen Astronomical Observatory, Japan)
The CCD image was taken on 1999 July 8.68, using a 0.60-m f/6 Ritchey-Chretien telescope.
During the last half of November of 1990 Carolyn S. Shoemaker (Palomar Observatory, California, USA) discovered images of an asteroidal object on plates taken on October 25, November 13, and 15. The magnitude was estimated as 17 on October 25 and 17.7 on November 13. The plates were obtained by Eugene M Shoemaker, David H. Levy, and herself.
Prediscovery images were then located on plates exposed at Palomar Observatory by H. E. Holt, H. R. Holt, C. M. Olmstead, and J. A. Brown on September 17 and 20. The magnitude was determined as 17.6.
Gareth V. Williams took the available positions and computed an elliptical orbit with a perihelion date of 1990 September 25 and an orbital period of 9.27 years. He said the orbit indicated this was a Jupiter-crossing object. The object was given the minor planet designation of 1990 UL3.
Brian Skiff (Lowell Observatory, Arizona, USA) announced that CCD images obtained with a 1.1-m reflector on December 7 revealed a straight tail extending 29 arc seconds toward PA 67°. Before this announcement, S. Larson and Levy (University of Arizona) obtained CCD images of the comet with the Catalina 1.5-telescope on December 19 and detected a tail extending 28 arc seconds toward PA 58°. Thus, the "minor planet" proved to be a comet.
During the discovery apparition the comet was only followed until 1991 January 15, when astronomers at the Anderson Mesa station of Lowell Observatory detected it. They determined the nuclear magnitude as 18.2.
After acquiring all available positions, S. Nakano determined a revised orbit which indicated the comet would next reach perihelion in February of 2000. Searches actually began in 1998, and on May 19 and 20 C. W. Hergenrother recovered the comet with the 1.2-m reflector at Mt. Hopkins. His precise positions indicated Nakano's prediction required a correction of only -0.5 day. Hergenrother said the comet appeared stellar in appearance and had a magnitude of 21.0.
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