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Reports from Geisei Observatory <September 12, 2007>

The elusive photograph of the comet C/1992 N1(Machholz)

    I have finally found the elusive negative of Comet Machholz C/1992 N1! It is an extremely faint image. I had vainly searched every corner of the storage for more than a week, and found it, of all places, in a drawer of my desk I sit at almost everyday.

    I realized why Mr. Machholz had been looking for this photograph. There are only few observations of this comet. The comet was discovered in the predawn northern sky near Gemini on July 2nd 1992. It was visible for only about one week and lost forever after my observation on July 10.

    I watched this comet with the 20cm refractor at 40x, which was mounted on the 60cm reflector. The coma was about 3' in diameter with a faint central condensation. The tail was trailing faintly to the north for about 2' in length. It was 9.5 magnitude. It was discovered under very difficult conditions in terms of its position and there was no other independent discoverer.

    In those days Mr. Machholz was using 27x12 cm binoculars for comet search. It was designed for astronomical observation with a 3.5-degree-wide field. Geisei's Nikon binoculars are 20x12 cm and I believe the 12 cm binoculars need a magnification of 25 power to see comets clearly.

    There were only 9 observations of this comet including 4 made at Geisei. Observations at Geisei those days were made using a very limited number of comparison stars in the SAO resulting in an unsatisfactory level of accuracy. I have remeasured the two images I had found, this time, using the GSC and a more precise measuring system.

    These are the last observations of Comet Machholz before it disappeared soon after.
C/1992 N1 (Machholz)                                   
1992UT          R.A. (2000.0) Decl.         m1         
July10.78403  05 21 04.94  +30 48 05.6     12.5     372
    10.78715  05 21 05.73  +30 47 57.0     12.5     372
    *The magnitudes given above are photographic magnitudes by the 60cm reflector using TP6415 film.

    This image on the negative is very faint, but I would ask Mr. Shimomoto to apply image processing to make it more visible and will have it sent to Mr. Machholz via Mr. Kato. The processed image will be presented in the Memorable Comets section later.

C/1992 N1 (Machholz) captured on TP6415 film

    The area marked by a red square in the above photograph was scanned and is reproduced below. Comet Machholz is indicated by two red lines.
The stars marked by blue circles were used for measuring the comet's position.

C/1992 N1 (Machholz)

Copyright (C) 2007 Tsutomu Seki.