Reports from Geisei Observatory <June 13, 2008>
Photographs of Geisei's 70cm reflector and C/2008 J1(Boattini)
Mr. Shimomoto, a staff member of Geisei Observatory, has
been testing the CCD capabilities of Geisei's new 70cm telescope, while
I have been testing emulsion-based photography with the new telescope.
The photograph below is that of recently discovered C/2008
J1 (Boattini). The computer system slews the telescope with the sidereal
time and performs Metcalf guiding at the same time by following the comet's
motion . This makes photography easy. During a rather long 10-minute exposure,
the telescope was guided all automatically.
The f-ratio of the 70cm reflector has been problematic, but
f/5.8 is now achieved by the use of a reducer lens and adjustment of the
position of the camera. However, f/5.8 is still too slow for comet observing.
C/2008 J1 has a solid nucleus and a fast optical system will
capture the coma much more extensively. This comet will soon become possible
to observe visually. It may be around 11th magnitude at the moment. The
magnitudes announced by Geisei are of the nucleus.
C/2008 J1 (Boattini)
10-minute exposure from 00:20, June 13, 2008 JST
70cm f/6 reflector TMY 400 film
Copyright (C) 2008 Geisei Observatory