Re: [ATM] Calculate Astigmatism

["Donald \"Don\" Ware" <mimas@charter.net>]

----- Original Message ----- 
From: "Stephen C. Koehler" <koehler@securecomputing.com>
To: "Michael Peck" <mpeck1@ix.netcom.com>
Cc: <atm@atmlist.net>
Sent: Wednesday, March 24, 2004 12:07 PM
Subject: Re: [ATM] Calculate Astigmatism

>>>>
Couldn't you use the measurement of the center zone on each data
set as a baseline, or at least make the assumption that your innermost zone
is not much affected by astigmatism?  This would eliminate the need to
maintain the test rig distance over a mirror rotation.
<<<<<

This assumes that the astigmatism is symmetric about one diameter of the
mirror.  I have yet to see an astigmatic mirror that exhibited such a
symmetry.

It is relatively simple to build a foucault tester that rotates, allowing
testing along multiple axes without the need to move the mirror.  The tester
to mirror distance can then easily be kept constant within the tolerences
being discussed.  See my web site for details of such a tester.

Regards,

Don Ware
Hollis, NH
http://webpages.charter.net/dware1/




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