From: Alan Friedman <alan@greatarrow.com>

Date: February 28, 2008 1:41:04 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: More New Images!

Hi all,

Thanks for the images - I've been enjoying them from travels in balmy Washington DC. The saturn shots show well the ring brightening that is observed around opposition - nice work!

On the issue of scopes, I find that for imaging, increasing aperture represents an advantage in almost all seeing conditions. With poor seeing (below 4 Pickering) it is likely that there won't be enough (if any) really sharp frames to make the time spent selecting and stacking worthwhile. At 5-6 pickering I find that there are very good frames and a good or very good image can be obtained. As the seeing improves, the number of very good frames will increase and there will also be a qualitative increase in sharpness in some of the very good frames. In these frames (representing the brief steady moments, perhaps 15-25% of the total frames) , the advantages of extra light and resolution afforded by moving up in aperture is tangible and will be clearly visible in the final image. No question it is better to be in Florida, but the same relative results will be seen anywhere - assuming of course that the equipment is of good quality, collimated and at thermal equilibrium with the ambient temps.

I'm at an age and location (no permanent observatory) where a 35 pound 10" scope represents a sweet spot. But it is very hard to argue with the best work being done with 14" Celestron SCTs.

For visual observing I think personal preference and observing style make for a much more open ended discussion on what is the best planetary scope. For imaging - choose as good as you can afford and as big as you can lift!

best wishes,

Alan