February 2008

February 11
Comet Kojima, the last observation with the 60cm reflector at Geisei

    Mr. Shimomoto coined the word "last light" referring to the last observation by a particular telescope, as opposed to first light. "Last light" captured by Geisei's 60cm reflector was that of periodic Comet Kojima (70P/Kojima).
    I wonder how many thousands of photographs Geisei Observatory have taken since it began to operate in 1981. The last of these countless photographs is that of Comet Kojima presented here.
    There are a number of interesting episodes about Comet Kojima of 1971. I will soon reveal them in "The Stories of a Comet Hunter's Life". It is perhaps not widely known that the discovery of Comet Kojima became a trigger for the first Comet Conference. Three names (Tsutomu Seki, Hisanobu Kojima, and Ichiro Hasegawa) are given in Yamamoto Circular #1733 as the organizers of the first Comet Conference, which had been edited and published by Mr. Ichiro Hasegawa.
    The interesting thing is the association between Comet Kojima and Neujmin 2 (25D/Neujmin 2). The latter has been long lost. Though these two comets were determined to be separate comets, their orbits are so similar that you would be tempted to believe that Neujmin 2 turned itself into Comet Kojima.
    Recently Mr. Kojima has sent me images taken by a 25cm-telescope equipped with a CCD camera. It seems that his passion for comet discovery has returned to him and begun pursuing his old dream.
    On February 13, Goto Optical began working to dismantle and remove Geisei's 60cm reflector, which they had built. Beautiful stars will continue to shine over the empty observatory dome. The radio program "Midnight Letter" was produced by NHK, in which I reminisced about the 60cm reflector. It will be broadcast again on March 10.


February 8
Tenacious Comet Holmes

    17P/Holmes is quite a tenacious comet. From Geisei Observatory it is still easily visible. The coma is large and fluffy like cotton candy. On February 8 it took up a third of the 10x70 binoculars' 5.1-degree field, which means it is as large as 1.7 degrees in diameter. However, the diffused coma was invisible in the 20cm refractor at 40x and it seems the naked eye or binoculars to be more suitable for seeing it.
    It is very difficult to estimate the total magnitude of the comet when it takes on this sort of appearance. M33 in Triangulum, for example, is listed as a 7th-magnitude galaxy. Though it looked very faint through the 188cm reflector at Okayama Astrophysics Observatory, which I visited about 30 years ago, it was faintly visible to the naked eye at Geisei Observatory. It is hard to believe but true. Comet Holmes has an unusually diffused coma. If all the glow in the coma were concentrated at a point, it would be surprisingly brighter. This is a peculiarity of the total magnitude.
    While looking at this tenuous Comet Holmes, I remembered an episode about Earth's second satellite. About 40 years ago, a certain astronomer made a claim that a dynamical effect collected space dust at a position 90 degrees away from the Moon and formed a tenuous second moon. He even traveled to a very dark site in the Tetra Mountains of Czechoslovakia (present Slovakia) and reportedly confirmed it with a 35mm camera. When this story became known widely, Mr. Ike, who had an inquisitive mind about curious incidents, climbed Ishizuchiyama mountain (elevation 1982 meters) on one freezing wintry day and attempted to photograph this "moon" with a 35mm camera equipped with a short focal lens. Shortly after the discovery of Comet Ikeya-Seki, Mr. Ike traveled far and wide looking for a chance to witness Ikeya-Seki, even risking his life at times. He lived up to his reputation as an "astronomy adventurer Ike".
    Staring at faint and diffused Comet Holmes, I wondered if the "second moon" resembled this tenuous appearance of Comet Holmes. My thought drifted over to the fond memories of those old days.