On 9/21/11, erikhansen@thebluezone.net <erikhansen@thebluezone.net> wrote:
It should be an interesting project, I would be glad to help you test it out. I was generally referring to traditional mountings of refractors. Your concept seems more catered for longer focal length, IE folding optical path reduces length. I have seen some folded refractors at RTMC in the past, I find them impressive.
The optical path in a Gerrish is folded in front of the objectve, not behind. The optical tube itself is straight-through, totally conventional, and can be removed and installed on any other mount. The tube is inclined at the latitude of the observer, and you need room below the objective for the flat mirror, so a 6" f/10 could actually put the eyepiece around 5 feet off the ground. That's why I said the f/5 might be better, since we would lose 30 inches in tube length. I have an elliptical, 9" minor-axis flat that I plan to use. So in practice it would accommodate up to about 8.5" aperture.