Reports from Geisei Observatory<August 2, 2000>

• Disintegration of C/1999 S4(LINEAR)
Rain has been falling for days. On August 1 I rushed to the observatory as soon as I found a little blue sky in the south in the evening praying for a one-in-one-million chance. What has happened to LINEAR after perihelion passage on July 26? I turned the 60cm telescope to the correct predicted position of the comet in the low clouds in the west and waited patiently for breaks. At 20:20, when the twilight was just about to end, the stars popped into view suddenly in the 20cm refractor mounted on the 60cm telescope and LINEAR was shining at the center of the one-degree eyepiece field. It was a huge, hazy, diffused coma and I was able to discern a 30'-long tail. However, it was extremely faint and the nucleus lost its intense brightness as seen previously. It looked like just the remnants of the comet. It was difficult to estimate the brightness but overall it was relatively bright 7th magnitude. The diameter of the coma-like object was about 10'. At 20:35 using another brief breaks in the clouds though drizzling, I took a photo of the comet with a 3-minute exposure by the 60cm reflector. I was worried if the big reflector with a large focal ratio could capture the diffuse comet, although it was detected visually.

For the photograph below TM400 film was processed by D-19 (high-contrast developer). Can you see the image of the comet?

In 1965 Comet Ikeya-Seki disintegrated after perihelion passage on October 21 like LINEAR. The coma was bloated like a balloon without any nucleus. I remember a report that it was visible in the 15cm finderscope but not captured by the 91cm f/5 telescope at Dodaira Observatory. I also remember that the last image (by a 35mm camera) of Comet Ikeya-Seki taken in the south in January 1966 resembles this disintegrated comet LINEAR. The very photograph is contained in the now out-of-print "The Special Photographic Collection of Comet Ikeya-Seki" by Seibundo-Shinkosha Publishers.

I hope to try one more time using Konica 3200, if there is any chance. There are only a few more days left for this opportunity, but heavy rains continue to fall today.

C/1999 S4(LINEAR)
3-minute exposure on August 1, 2000
Film: TM400 developed by D-19 (high-contrast developer)
60cm reflector at Geisei Observatory