Re: [ATM] testing convex surfaces by reflection - a thought experiment

[Jim Burrows <burrjaw@earthlink.net>]

At 2008-01-26 12:16 -0800, David Weinshenker wrote:

>It may be argued that using this method to test a convex surface
>requires the availability of a pair of "known good" telescope lenses,
>just as the basic autocollimation test requires a "known good" flat
>mirror... although the test could easily be conducted in monochromatic
>light - at which point the lenses do not need to be achromatic, though
>they should be free of spherical aberration.

This sounds somewhat like the refractive null tester used (not 
enough) by Perkin Elmer on the Hubble primary.  Much easier for the 
ATM to test convex mirrors is the Hindle test - it's easy to make 
very precise spherical mirrors, much easier than flats (gotta make 3 
o'them).  The Hindle test can be run non-null, so you don't need to 
have a precise ROC of the sphere.

         -- Jim Burrows
         -- http://home.earthlink.net/~burrjaw
         -- mailto:burrjaw@earthlink.net
         -- Seattle N47.4723 W122.3662 (WGS84)

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