I'd agree with Mike that larger scopes are viable for planetary viewing. The best views of Jupiter I have ever had are through larger scopes. Lyle Urich's 18" at TIMPA one spectacular night at up to 1200x, and a much larger scope on Kitt Peak, both scopes used full aperture. In my experience the larger scopes do provide the more detail as the physics of diffraction would dictate. But I have also seen times where a smaller aperture is just less subject to atmospheric seeing effects. This was more than clearly demonstrated on night at Yavapai point during GCSP, when when dawn came there were three scopes that hadn't been put away during the night, a 41", a 28" (Dennis Young's) and my 8". But when morning came everyone was looking through my 8" as Jupiter and Saturn had risen before dawn and the difference in the image was remarkable in the less than steady air, even given approximately the same magnification. The seeing effects were there in the 8", but the image just seemed to wander and the eye could easily correct. While in the larger scope the image seemed to blur and come back. I have listened to the adaptive optics people at Steward and the theory of wavefronts and cells of seeing, but nothing makes more of an impression than that morning walking between the scopes and directly comparing the view. But then the best view of Mars I had this opposition was through my own 18", again at full aperture. Now if only I had a decent secondary in it! (Working on that) Andrew Mike Spooner wrote: > > I've been busy testing out an 18" personal mirror for my big Dob the past > few weeks and thought I'd pass some observations along... -- Andrew Cooper Tucson, AZ mailto:acooper@xxxxxxxxx http://whitethorn.house.home.att.net --- This message is from the AZ-Observing mailing list. If you wish to be removed from this list, send E-mail to: AZ-Observing-request@xxxxxxxxxxxxx, with the subject: unsubscribe. The list's archive is at: //www.freelists.org/archives/az-observing This is a discussion list. Please send personal inquiries directly to the message author. In other words, do not use "reply" for personal messages. Thanks.