Message posted by spotting wolf on August 25, 2004 at 7:58:45 PST:

I've been doing most of my photography with a refractor and 4x barlow. If you go reflector, you should get a 5 inch aperture. [The hole in the middle reduces sharpness.] For refractor, 3 inch aperture will do. The image under poor seeing conditions will be better with the smaller aperture refractor. [Tikaboo to Groom is 26 miles, so the seeing is always poor. In astronomy, you only deal with 3 miles of atmosphere, so most of the writings on the topic of poor seeing are just barely relevant. You only have 2 miles of atmosphere if you live in Rachel. ;-)]

My biggest complaint about reflector telescopes is the light fall off as you head towards the edges. The effect is very evident in panoramics. To fill the 35mm frame with a small reflector scope, you will need a teleconverter or barlow. [No big deal if you are shooting fom Tikaboo as you need the magnification.] The light pipe off a small reflector won't fill a 35mm frame. If you get a refractor, make sure it can accept a 2 inch visual back so that it can be used under prime focus.

There really are no bargains out there, though you can save a bit using astromart.com classifieds. One way to save money would be to get a achromat (versus apo) refractor, then use a bandwith limiting filter. These go under various names, but UV-IR filter or minus-violet filter should get you a few hits. A cheaper solution to the minus-violet filter is to shoot through a green filter on b&w film. Green is in the middle of the visible spectrum, so the filter attenuates the edges of the spectrum that cause blur in an achromat. The disadvantage to the green filter is more light loss, hence slower shutter speed.

In Reply to: Spotting Scopes? posted by Trevor on August 25, 2004 at 2:06:44 PST:

Replies: