Jump to top page

Reports from Geisei Observatory <August 21, 2006>

A story of the mysterious comet Tuttle-Giacobini-Kresak

    I have written in an earlier report that Dr. Kresak of Czechoslovakia (presently Slovak Republic)visually re-discovered this long-lost comet in 1951 while searching for a new comet. The story here is about very unusual and amazing developments and Geisei's comet telescope also played a prominent role in it.

    The mirror of Geisei's comet telescope was made by pouring melted glass into a mold, which is commonly believed to be worse than blue plate glass. The equatorial mounting to support this telescope also turned out to be a lemon built by N company with a periodic error of as much as 40". I was just able to overcome the deficiencies of this telescope only with my skill and experience. In spite of a trying and hopeless situation like this, I was full of passion and enthusiasm for observing with the newly installed comet telescope.

    Strange, new developments all started in 1973. For the 1973 return of Comet Tuttle-Giacobini-Kresak the prediction of the positions had been published in BAA Handbook by Milbourne and others. It was predicted that the comet would pass perihelion on May 29 and reach a maximum magnitude of 14 from May to June. In mid June, however, we were surprised by a telegram from Smithsonian to report that the comet had brightened to 4th magnitude displaying a substantial tail. This made Dr. Marsden even wonder if this was a completely new comet with a similar orbit and requested Japanese observers and others to verify it. Unfortunately, we were in the middle of the rainy season and nobody in Japan was able to observe this comet. This "new comet" turned out to be Tuttle-Giacobini-Kresak in outburst and it became 10 magnitudes brighter than BAA's prediction. Dr. Kresak, a theorist and one of the re-discoverers of this comet, expressed his view that the comet might have lost most of its energy by this outburst. Because of this, Dr. Marsden published his prediction for the comet's 1978 return in BAA Handbook that it would reach incredibly faint 20.4 magnitude. Furthermore, the comet would have to be observed in the worst possible conditions; low altitudes in the predawn sky. This would certainly discourage observers from searching for it.

    Against such odds there was one telescope searching for the approaching comet under freezing pre-dawn December skies hoping for the comet's outburst. It is, of course, Geisei's newly installed comet telescope. "The comet must have regained some brightness", I believed and turned the telescope to low eastern skies in the approaching twilight

    Looking into the finderscope, I was stunned. Venus at its maximum brightness was glaring at the center of the field. Though I thought it would be impossible to photograph the comet, I made short exposures one after another, thinking just in case... It was several days later that I found the comet was captured on one of the plates. I was able to determine its position away from Venus and my earlier measurements became useful. This was probably the first achievement by the comet telescope. At the same time I came to believe strongly that efforts, though not promising, could pay off.

    I have found only one photographic plate with the comet on it. Across the field it is hazy due to a ghost image of Venus. I wondered what Dr. Kresak and the Japanese astronomer Mr. H thought of the comet's recovery by Geisei. They had expressed a pessimistic view about finding the comet.
1978UT        RA (2000.0)   Dec           m1         
Dec.11.84583  14 39 34.21  -11 38 18.8   14.9     372

16-minute exposure from 05:10, December 12, 1978 J.S.T.
40cm f/5 reflector, 103a-O photographic plate

Copyright (C) 2006 Tsutomu Seki.