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Old 02-05-2007, 08:43 AM
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rmcpb (Rob)
Compulsive Tinkerer

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Join Date: Jan 2005
Location: Blue Mountains, NSW
Posts: 1,766
All these off axis scopes use part of a MUCH larger parabolic mirror as their primary. You throw away lots of expensive glass to avoid the central obstruction. The general concensus is that while these are interesting projects as soon as you get over about 6" and into shorter focal lengths you are much better off witht he complete mirror and a relatively small central obstruction.
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