Copyright © 1999 by Akimasa Nakamura (Kuma Kogen Astronomical Observatory, Japan)
The CCD image was taken on 1999 January 13.45, using a 0.60-m f/6 Ritchey-Chretien telescope. Three images were added to better reveal the comet. Subsequently every star appears three times.
Discovery
C. W. Hergenrother discovered this comet on CCD images obtained by T. B. Spahr with the 0.41-m f/3 Schmidt telescope in the course of the Catalina Sky Survey on 1998 November 21.10. An additional image obtained on November 21.12 showed the comet moving northeastward. He estimated the magnitude as 17.3 and said the comet was moderately condensed with a broad tail extending 30-60 arcsec toward PA 80°. Additional images were obtained on November 22.
Historical Highlights
The first orbit released for this comet was a parabolic one computed by Brian G. Marsden (Central Bureau for Astronomical Telegrams) and published on IAU Circular 7057 (1998 November 23). Based on positions gathered during the period of 1998 November 21 to 23, he determined the perihelion date as 1998 November 26.13 and the perihelion distance as 1.56 AU. The low inclination prompted Marsden to suggest the comet was "probably of short period." On December 18 the Central Bureau issued MPEC 1998-Y15. It indicated that further observations had confirmed Marsden's suggestion that the comet was moving in a short-period orbit. Based on 37 positions obtained during the period of November 16 to December 17, Marsden determined a perihelion date of 1998 December 6.06, a perihelion distance of 1.42 AU, and an orbital period of 6.78 years.
Initial observations soon after discovery indicated the comet was around magnitude 17.5. With the comet passing perihelion in early December it began fading as its distance from Earth also increased. By mid-December the brightness had declined to magnitude 18 and it reached 19 by mid-February of 1999. It was last detected on April 15.14 by observers at the Catalina Station (Tucson), at which time the magnitude was given as fainter than 20.
Following the final observations of this comet, Patrick Rocher refined the orbit of this comet. Rocher used 76 positions obtained between 1998 November 21 and 1999 April 15 and determined the perihelion date as 1998 December 5.946, the perihelion distance as 1.420 AU, and the orbital period as 6.906 years. He estimated the period's uncertainty as ±0.1436 day.
Additional Images
Copyright © 1998 by Catalina Sky Survey, University of Arizona
These images were taken by T. B. Spahr on 1998 November 21. He used a 0.41-m Schmidt telescope. These were the images Hergenrother first discovered the comet on. Note that in the first frame, the comet was partially covered by the vertical line cutting through the image.
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