Quote:
Originally Posted by mswhin63
I suspect the lens in mine was used to compensate for short tube to give better spec.
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Sort-of yes - the corrector lens (a 2x barlow usually) allows the physical tube length to be around half the optical focal length.
My understanding is that the design achieves two things:-
1. Shorter tube length, hence more compact as well as less material used (= less cost)
2. Allows the use of a spherical mirror - cheaper to produce?