[ATM] Rating mirrors,understanding seeing

[jeff newsom <triolian@earthlink.net>]

After looking at the pages of several different optical companies(Royce,Obsidian, Pegasus and so forth to name a few) and the writings of Mel Bartel, Bob May and others, and articles on optics and texts on optics(Texerau, Kriege Berry) , I'm still trying to get  a handle on what magnifications , on average, one  should expect from say, a 12" , f/7 or so on any given night. Mel seems to be able to push his mirrors consistently to magnifications well beyond anything else I've seen(1000x)(Where the hell do you use that thing Mel? In a vacuum?  ;) ). Most "companies "seem to suggest that 350 to 400x is more the norm as a top end , with magnifications routinely in the 180,275 range, which is where I seem to be with my most recent 12" , f/7.3 mirror.
   Now , I understand that "seeing" conditions vary greatly and are a key component in how far one can push magnification.  Last night, I was able to split the double -double , Epsilon -Lyrae. But this lasted only a moment here , a moment there, with a bit of fuzziness(in the star images) present thoughout. Still , at times, there was a definite break between the individual components of each double. Now, conditions were obviously not ideal, with some flickering of stars even near the zenith. I was using a Siebert 9mm ultra giving me a magnifaction of 245X. My star test reveals a good figure, but with perhaps a fuzzy edge inside of focus. The mirror has 1/4" off masked already. Will poor seeing create the fuzzy edge inside of focus? Will a "great" mirror split the double -double  readily in all but the most marginal of seeing conditions??
   I guess what I'm really after here is where do most of you folks end up magnification-wise, on average, understanding of course aperture and focal ratio considerations, local climate , etc......... Thanks---Jeff Newsom
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