Quote:
Originally Posted by ausastronomer
The 10" BK7 mirrors in the GSO dobs are very good, mine is actually outstanding for a mass produced mirror. Base your decision on which scope to choose on factors other than the mirror substrate.
CS-John B
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BK7 bends its shape *3X* more than Pyrex for a given residual difference between mirror and air. Effect not so prominate on a lightweight 10" that is only a slight asphere..effect will be much more obvious on a larger slab of glass whose mass is goin up by the cube root of the aperture.
Mark