Re[4]: [ATM] A two way null test for convex hyperboloids

[Richard <cnc@cncservo.co.uk>]

Hi Mauritz,

Wednesday, April 6, 2005, 10:34:32 AM, you wrote:

MA> Yes, it does depend on the index of refraction.
MA> The choice of a quartz subtrate was arbitrary, but perhaps a bit stupid.
MA> Here is the prescription for a BK7 substrate instead,

MA> The sensitivity to testing wavelength is not too big, this example would give an
MA> ok null also for Na light 589 nm with a
MA> source/knifeddge distance of 673.4 mm.

Well, I'm using a different program to you, but I still don't
get a good null. With BK7 and 632.8nm I see 1/4 wave pv on the
wavefront. It improves to 0.066 nm pv with Na lightwhich still
isn't that good as null tests go. If I choose to optimise for
the wavefront error I can get a much better null, but now the
source and image are 100mm or more apart.

What pv error are you seeing in the nulls you have posted?

-- 

Best regards,
 Richard



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