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December 2007

December 6
Comet Holmes has become large and diffused.

    I went to the observatory today with Mr. Uchi, an announcer from NHK's Kochi broadcasting station. We went there to work out details on site for a radio program called "Midnight Radio Mail" to be broadcast in January. When I arrived at the observatory, there happened to be staff from Nishimura Optical Company including Mr. Kawauchi, head of the company's sales department. They were inspecting the dome in preparation for constructing a new observatory for Geisei. In Midnight Radio Mail we will talk about astronomy for 40 minutes from Geisei's dome in late January. I will tell the listeners interesting stories about Geisei that have never been told before. According to Mr. Kawauchi, the 70cm mirror for Geisei Observatory is now being ground and polished in Russia and the construction work for the new observatory will begin on site in February.
    Soon after the end of twilight, Comet Holmes became visible. To the naked eye it was as bright as a nearby 3rd magnitude star, but in the 20cm refractor at 40x the coma was completely invisible. It was not captured in photographs taken by the 60cm f/4 reflector, either. However, in 10x70 binoculars and to the naked eye the coma was easily visible. At the 18:30 observation the total magnitude was 3.2 and the coma was 50' in diameter, about a 1/6 of the 5.1-degree binocular field. DC was 4 and both transparency and seeing were 3/5. The comet has faded, but continues to expand. It may be visible to the naked eye until the end of the year.
    8P/Tuttle has brightened to 10th magnitude and is easily visible in the 20cm refractor. Due to the approaching low pressure system, clouds began to increase from 20:00 and I decided to go home.
Copyright (C) 2007 Tsutomu Seki.