Quote:
Originally Posted by toyos
There's an obvious difference in image quality between a scope with 0% obstruction to one with 18% obstruction.
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Theres a subtle difference but its not enough to make one want to shell out for a non portable 10" apo refractor at 10 times the cost of a premium reflector. As a rough rule of thumb the equivelent contrast transfer function will be equalled by a quality reflector of diameter larger than the refracter by the diameter of its secondary.
I can vouch for this rule. Years ago ,we had a stock standard AstroOptics 10" F6 Newt beside a 7" F9 Astrophysics starfire on Jupiter. The view in the 10" Newt simply blew the 7" away as there was little color differentiation in the refractor and at magnifications enough to resolve small features the view had broken down in the 7" and was still lusterous in the 10". It was a poignant moment when I looked around and saw the 7" was layng idle after so much fuss had been made as it was set up. It was a $12K rig and that would have been 15 years ago.