Message posted by lone wolf on February 12, 2003 at 11:42:40 PST:
Dawes limit relates resolution to aperture, so intuitively you would think bigger is better. However, at 26 miles of distance, the atmosphere is the limiting factor, not the telescope aperture. In fact, in "poor seeing" conditions, smaller aperture is often better. ["poor seeing" is a common astronomical term, so you can do a google on it to get more information.] Unless you need more light, larger aperture is not needed. Note that for astronomy, there is only about 3 miles of atmosphere between you and the target. Now magnification and aperture are not the same thing. It's been my experience that you really can't use more than the equivalent of 4000mm to photograph the base, and in fact half that is sufficient if your film has fine grain. Remember that as you double the magnification, you get 1/4 the light which requires a slower shutter speed, which in turn makes the set up more sensitive to shake. The key is the ability to focus and to maintain focus. You need a magnifier on the viewfinder to focus. I use a 6x and I really don't think that is enough. I was given a 10x microscope objective that I'm going to try to hack as a focus aid. Lastly, you need to carry all this crap on your back, plus water, tent, sleeping bag, pad, scanners, food, etc. Then you hike up a 100% grade of loose shale with 50lbs on your back. You need to evaluate everything you carry before heading up the hill. Case in point, I picked up a cheap mp3 recorder to save scanner audio because I didn't feel like lugging a casette recorder up the hill. Like the song goes, everything counts in small amounts.
In Reply to: Tikaboo Qtn posted by Adamk on February 12, 2003 at 11:19:31 PST:
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