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December 2008

December 28
    Many of you may not be aware of existence of two Ikeya-Seki comets. The second Ikeya-Seki (C/1968 Y1) was discovered on the morning of December 28, 1968. The time difference between the first sighting of the comet by Mr. Ikeya and the second sighting by me was only 5 minutes. This difference testifies that how seriously the two observers were searching the sky and that once they detected any change both would turn their telescopes immediately to the spot where the change was taking place. I think both of us were observing under extremely harsh conditions physically and mentally.
    This comet was discovered in the early morning of a day when we were struck by a very strong cold wave. The comet was low in the southeastern sky and I remember it was at 10th magnitude. Mr. Ikeya was using a 15cm reflector at the shore of the lake of Hamanako in Shizuoka prefecture, while I was observing with 20x12cm Nikon binoculars in Kochi city.
    This comet is unforgettable in that it showed me a future direction for my comet search. Until the discovery of this comet, I had been looking for a new comet using a comet seeker alone. However, this discovery became a turning point in my observing and I began photographic observation as well as astrometric measurement using a reflector.
    In those days, the precise astrometric measurement of comets and minor planets was a very difficult task for amateurs who were not adequately equipped. I think it was in 1969 when I made the first positional measurements of a comet and reported the results to the Smithsonian. This stunned Dr. Marsden and asked the late Mr. Koichiro Tomita at Tokyo Astronomical Observatory: "How on earth is Seki making positional measurements?" In those days, comet observers were highly valued because even professional observers making positional measurements were very few and could be counted on five fingers. In these circumstances astrometric observation by amateurs was simply unthinkable.
    Among those few professional astronomers and observatories engaged in comet observation were Dr. Elizabeth Roemer of the U.S. Naval Observatory at Flagstaff, Dr. George A. Van Biesbroeck at Yerkes, Skalnate Pleso in Slovakia, Tokyo Astronomical Observatory, and Kwasan Observatory in Japan.
    For amateurs observers, making positional measurements was not easy. First of all, they were unable to get hold of accurate stellar catalogues. Comparators to measure positions on photographic plates or film were not widely available either and the only one purchasable in those days was a photographic plate measuring instrument made by Shimadzu Corporation. However, the price was 500,000 yen at the value of the 1950s, prohibitively expensive for an amateur like me who was "sponging off" my parents at that time.
    In a difficult situation like this, I came up with an idea and put it to practice. It was a rather bizarre method and have kept it to myself until now. It was also the important starting point for developing the present observation method of comets at Geisei Observatory.

(to be continued)

Copyright (C) 2008 Tsutomu Seki.