Re: [ATM] Stubborn Oblate Spheroid.. update

[Jim Burrows <burrjaw@earthlink.net>]

At 2005-09-22 00:08 -0400, Jason Hissong wrote:

>Here is the final ronchi diagram prior to figuring (another 45 mins of
>MOT, 1/3 diameter W strokes):
>...
>
>This is an F4.3 mirror so figuring should be an adventure!

Also testing.  Suiter has a long appendix on Ronchi testing, p. 289-297, 
the overall comment being that diffraction messes it up so much that it is 
nearly impossible to tell whether the mirror is passing or not (but Mel 
Bartels has a longitudinal variant of the Ronchi test which might be an 
improvement, but Suiter dismisses it, "Unfortunately, the test is almost 
never undertaken in this manner, probably because it so closely resembles 
the Foucault test that the user was trying to avoid in the first 
place.")  Foucault is a better choice, but not easy at f/4.3.  You might 
investigate Foucault variants, such as the Everest pin stick test and the 
Lateral Wire Test (LWT).

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

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