Re: [ATM] Strange Chinese Telescope Design f/3.6, spherical mirror

["Bob May" <bobmay@nethere.com>]

Guy, test the scope as a unit rather than testing the primary.  You may
actually be looking at a different beastie than the typical Newt, having
some optics in the focuser may end up doing a subdiameter corrector.  The
idea of all spherical optics is a wonderful thing for the optical maker as
it allows him to build the stuff that is easy to build and put together.
If the scope is indeed having troubles with focusing, having a very soft
focus, the primary probably isn't parabolized like it should.
I do know that Jason did, for a time at the least, did spherical primaries
and no correction.  My next door neighbor bought one for her daughter
several years ago and I got to test it for shape and the Ronchi lines were
perfectly straight all the way out to the edge.
Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net

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