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.