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1/12 wave surface only amounts to 1/6 at the wavefront. That doesn`t sound that good to me. Also being a true Ritchey-Chrétien 2 mirror scope I always thought that they too suffer from coma unless there is some sort of corrective lense in the optic train? Correct me if I am wrong. A f/9 newtonian would have very little coma too, but it would be long!
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