Archived posting to the Leica Users Group, 1997/03/13
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]> >The adapter would come from Celestron for about $100 bucks maybe. They > >usually end up in a T-mount. (about $15) Check with your local > > > Nah. Hal doesn't say what sort of Celestron he has, but if it's one of the > standard Schmidt-Cassegrains, it takes a simple Photo Adapter, which runs > > i<snip> I haven't read the Scientific American article, nor have I even viewed this comet. Yet. I do have some comet photo experience. Using your telescope as a prime lens makes it a 1000 to 2000mm lens. This means an angle of view in the neighborhood of one degree. The comet's tail may span 3 degrees now, and may 'grow' to three times that in the coming 40 days. Taking a picture through the Celestron would only show the head, which might be interesting, but won't show the tail(s) in all their beauty. If the Celestron has a clock drive, use it as a mount for the camera with a moderate telephoto lens (called piggybacking). Celestron offers a piggyback adapter which mounts to the 'scope and has a 1/4-20 male thread for your camera or lens. Align the telescope (polar alignment) and run the clock motor and the setup will track the comet pretty well for probably up to a two minute exposure (The comet does move slightly with relation to the background stars). Exposure? Use an EV of about -4 (f/2 @ 20 sec for ISO 400) to capture most of the tail's beauty. This assumes you are at a reasonably dark site as light polution will greatly reduce your ability to see and photograph all the details. I have found that at 20 seconds on a tripod with 200mm (a good focal length to try for comets) I get a bit of star trails (due to earth's rotation), but piggyback on a clock driven telescope will get rid of the trails. At least you can do decently with a tripod up to about 20 or 30 seconds with a 135 (on a Leica M!). BTW, I like to use EV as a concise way to express the metered light value of an object It allows one to juggle around the aperture, shutter speed and film speed. HTH, Paul.