I have a friend with a homemade mirror and scope like Bill's 14.5 inch scope (see earlier thread). Mirror is better than 1/4 wave. The star test (See R. Suiter's book) proves it. ~50X/inch of aperture is the rule of thumb I use to determine the max power you can use on a scope. Perhaps 300X is about the best you can do on most nights under average seeing conditions. BUT there are nights when the air is steady and very high power viewing is possible. I have seen Saturn and Mars at nearly 600X and it's amazing! I did not read it about this in a book somewhere. I saw it for myself. Larger scopes can handle increasingly higher magnifications without a loss in detail. Don't believe me folks? Again, go to any star party and look through well made big scopes that are using 600x or more to view the planets or moon. You will be BLOWN away by what you can see! Also, the big observatories such as Keck, Palomar, Wilson, and elsewhere go much much higher than 300X without the use of adaptive optics. Also read the historical observing reports from astronomers in the 19th century. They frequently used magnifications well above 300X.
