jlg@lanl.ARPA (01/12/85)
For amateur viewing of comets, a rich field reflector (or better yet - a
Schmidt camera) should be used. Comet tails tend to cover a fairly large
part of the sky and be very dim. To photograph them well, you need low
magnifiaction and large light gathering ability. Professional Cometary
research observatories use Schmidt cameras with VERY low f-numbers (1-1.4).
I sent a more detailed statement to the original poster of this question
to the net. Maybe he will summarize further responses later.
------------------------------------------------------------------------------
If the Earth were a grain of sand, we'd all be REALLY tiny! (*8
James Gilesjlg@lanl.ARPA (01/12/85)
Sorry - I tried to send this by mail, but the mailer sent it back. I have something to add about the telescope selection criterions given in your summary. If you are mainly planning to use it to sight cometary objects, you should consider looking for the lowest f-number telescope you can find. Comet tails are VERY faint objects and are spread out over large areas. To photograph them well, you need lots of light gathering capability at low magnification. The telescope at the Joint Observatory for Cometary Research in New Mexico (joint project between NASA and New Mexico State University) is a 15 inch Schmidt camera with a focal length of (I think) 18 inches - that's f-1.2! When there were no comets we used to photograph quasars for other research. An exposure of less than 15 minutes was sufficient to see most quasars, as compared to several hours to several consecutive nights on other, more conventional scopes. In addition, comet Kahoutek (which was such a bust for most amateur observers) was VERY visible in the Schmidt camera. We had photographs of 20 degrees of tail visible on most nights. (Now you can see the need for low magnification, most amateur telescopes have a field of view at their lowest magnification of only one or two degrees. The Schmidt camera had a field of view of 8 by 10 degrees - so even with it we had to do two seperate exposures to get the whole visable tail.) For amateur cometary viewing, a rich field reflector scope is probably your best bet. ------------------------------------------------------------------------------ KEEP WATCHING! James Giles