Cruising on e-bay, I ran into some old Mamiya Sekor 300mm and 500 mm lenses for large format RB67 Mamiya cameras.
Some of these lenses ( mostly the non-APO ones) were reasonably priced ($ 300-400 range), the APO ones were about 1$K-1.5$
my questions are:
1) are these lenses any good as short focal length rich field telescopes?
2) How do the above prices compare with Modern APO triplets prices of similar optical parameters ?
3) has anybody ever used such old telephoto lenses as a scope ?
4) Would such lenses have excessive CA as compared to similar APO triplets available for similar prices ?
What is your opinion/experience with such lenses (for visual or AP use)