Re: [ATM] at what stage do I start foucault testing?

["Bob May" <bobmay@nethere.com>]

The foucault tester is not used until you have a polished surface
that you can take readings from.  The grain of a ground surface
won't provide any useful info at all with a Foucault tester.
If you want a detailed ROC of the mirror, you can wet the surface
at any time and use a flashlight (no lasers!) to get the
flashlight test done.  This will give the ROC of the mirror to
about 1/2" or so which is much more than close enough for
grinding purposes, especially on a Newtonian mirror.
I'll also note that after you have the mirror polished, you can
then start working on the Parabolization of the mirror unless
you're doing something under F1 for a focal length.
Bob May
bobmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net
Replace the obvious words with the proper character.

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