To: amul49{at}eth.net, atm{at}shore.net
From: mdholm{at}telerama.com
Reply-To: mdholm{at}telerama.com


Aditya Munshi wrote:

>Is testing with an intermediate mask equivalent to testing with a mask
>of 7-8 zones, what I mean to say is that because I'm not an expert at
>Foucault testing ; testing with a 8 zone mask will no doubt have
>doubtful readings.

Yes, that is exactly why I made the intermediate mask feature in
CouderMask. It is difficult to use a mask with narrow zones.  Two masks
with nice width zones, offset to different radii is the way to go. 
Recently I even used three masks on an 8 inch mirror because of edge
trouble.  I had the normal 4 zone main mask, the 4 zone intermediate mask
and a special mask with two 1/2 width zones right at the edge.  Those
narrow ones were hard to read, but the results were very useful guiding me
to bring up a bad edge.

Mark Holm
mdholm{at}telerama.com

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