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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
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
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)