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Comet C/2002 O4

Michael Jäger photograph of Hoenig on July 28
Copyright 2002 by Michael Jäger (Austria)

This photograph was obtained by Michael Jäger on 2002 July 28.86. It is a composite of two 6-minute exposures obtained with a 200/300 Schmidt camera and Kodak Ektachrome 100 film.


Sebastian Hoenig (Dossenhiem, Germany) was out observing deep sky objects with his 0.25-m Schmidt-Cassegrain telescope when he found this comet on July 22.003. He estimated the magnitude as 12 and gave the coma diameter as 2 arcmin. Hoenig had no sky charts with him at the time and the telescope was not perfectly aligned to the celestial north pole. Subsequently, his only option was to take a reading from his telescope's goto system. About 20 minutes later, Hoenig confirmed the object was moving northward. Hoenig then packed up his equipment and headed home. After grabbing a few hours of sleep, he woke up, did a few errands, and then checked the position with his available materials at home. No galaxies or clusters were in the area. He then performed a check on the web site of the Central Bureau for Astronomical Telegrams (CBAT). It revealed no known comets or other objects were within 5° of his position. He reported it to CBAT and noted the position might be off by one or two degrees. Attempts by Hoenig and others to find the comet during the next few days proved unsuccessful. At the request of A. Nakamura, K. Kadota (Ageo, Saitama, Japan) began searching for the object and managed to obtain an image of the comet with a 0.18-m reflector and a CCD camera on July 27.65. He gave the magnitude as 12.1 and described the comet as diffuse, with a coma 1.5 arcmin across and a tail extending 1.8 arcmin toward PA 213°.

Historical Highlights

  • The first orbit was published on the "comet" internet mailing list on July 28. Maciej Reszelski (Szamotuly, Poland) took 26 positions from July 27-28, and determined a perihelion date of 2002 October 1.78. As more positions were measured, the perihelion date turned out to be closer to October 2.01.
  • At the end of July, observers were visually estimating the total magnitude as about 9.5, with a coma 5 arcmin across. The comet quickly brightened to magnitude 9.0 by August 3 and magnitude 8.0 on August 10. This was a more rapid brightening than predicted and although it may be real, there is a possibility it is a result of observers switching from telescopes to binoculars after the first couple of days of August.
  • cometography.com