Quote:
Originally Posted by koputai
Just say someone had a spare 8" f6 newt, and a spare secondary from an 8" SCT...
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I guess the real question is can you do anything else with a spare f/6 Newtonian primary.
For a Schmidt the figure is wrong - it needs to be spherical, so it would have to be refigured.
In its present parabolic form, it's too slow to be any use as a Cassegrain or Gregorian, it really needs to be f/4 or less.
As for other designs... from memory I think there is in theory a viable design involving a moderately concave (yes, concave !) secondary that will result in a fast optical system - about f/3 in this case - but the focal plane is in the middle of the scope. If you had say a 16" or 20" primary mirror, it could work with a small CCD head stuck in there, but for an 8" the head is going to be a huge obstruction in the lightpath - and hence not really viable in this case.
This design is an old one - no-one ever built it to my knowledge because the focal plane was inaccessible - there's no way it could be used visually, and it was too challenging for photographic plates.
I've forgotten the name of this, will scratch around - maybe Satchmo knows.