Re: [ATM] what to do next Part 2

[Jim Burrows <burrjaw@earthlink.net>]

At 2004-07-06 17:01 -0400, David  Williams wrote:

>I've got a foucault tester and need to know how to use it.  Like do I 
>really need a Couder mask?

Yes, you need some sort of mask to make a quantitative test.  An 
alternative to the Couder mask is the Ritchey mask, actually a set of masks 
with just two matching narrow holes per mask.  It takes longer to do a test 
sequence with Ritchey, so it might be better as opinion 1½ (the real second 
opinion is a star test) for the final "Am I really close enough to the 
parabola?".

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

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