From: "Bob May" 
To: "atmlist" 
Reply-To: "Bob May" 


No, wrong.  The mask images can be captured just as easily as the full
image but, here is the reason, the image of the mask on the mirror is
basically uninteresting. What you will see is a big blank mask with a few
holes in it and one pair of the holes may match in brightness.  Seeing the
whole mirror surface gives the viewer a good idea of how the mirror is
shaped.  After that, knowing from test results in text of what the ROC of
each zone is will tell the viewer how close the image is to the proper
parabolic surface. Ronchi tests are a qualititave test of how smooth the
surface shape is but the quantitive test of how accurately that mirror is
to a parabolic surface is a lot harder to determine than with the Foucault
test. Bob May
http://nav.to/bobmay
bobmay{at}nethere.com
NEW! http://bobmay.astronomy.net

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