This discussion of collimation has been fascinating! I've owned my 10" Odyssey Dobsonian for almost 20 years, and I have never collimated it, unless I did so when I first got it (which I definitely cannot remember). Indeed, I'm sure I wouldn't know how to begin - even after reading all of these wonderful posts. If my scope is "off," I'm too much of a rank amateur to know the difference. I use my scope to look at planets, the moon, an occasional comet, and various Messier objects and easy double stars. Mostly, I use it to dazzle my family or some school, church or scout group. Since my limited knowledge is slightly greater than theirs (or my misinformation is beyond their detection) they think I'm a great astronomer - as often as not they call me an "astrologer." So, I read Chuck Hards' posting: "But if you are mainly observing deep-sky objects at low to medium powers with wide-field eyepieces, collimation can be off by a surprising amount with no noticeable effects on the imagery," and I figure I can probably go another 20 years without worrying about collimation. But then, in that same entry he said: "A fast system (say, f/4) of long effective focal length (i.e., large aperture), used for imaging at high power or planetary viewing or very close double star splitting, should be collimated very precisely," and I wonder if any of that applies to me, and if I should think about collimation. Unfortunately, I don't even know the f/ value of my scope. (It's a red tube about 4 ft. long with a 10" diameter mirror. Does that help?) I do look at planets (especially Jupiter, Saturn, Venus and Mars), but usually not with my high-power lense. I haven't noticed any difficulty in getting a crisp image by fine-tuning the focuser, so I don't know if my views would improve with collimation or not. Any advice from any of you REAL experts to an admitted rank amateur like me? To give you an idea of my lack of sophistication, when I first got my scope, I couldn't even figure out how to focus it. Patrick Wiggins took the time to patiently explain how to extend the focussing tube. Duh! Patrick, you're the greatest! Raeburn G. Kennard 12082 Joey Park Place Draper, UT 84120 (801) 321-4867 rkennard@kmclaw.com