Re: [ATM] Simple Foucault tester for astigmatism

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

Another approach to measuring astigmatism with a foucault tester
is to rotate the tester itself.

See the following webpage:

http://webpages.charter.net/dware1/foucault/Foucault.html

You need to use more care than usual in aligning the tester with
the mirror's optical axis so that readings of the central zone
don't vary as the tester is rotated.  Measurements with a dial
indicator show that the on-axis tester movement with rotation is
less than .001", well within the repeatability of the
measurements.

Don Ware
http://webpages.charter.net/dware1/

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