Re: [ATM] Spherometers and sphericity

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

Any furrow that you may dig with a piece of grit will go away
with the next wet, providing that the grit is the same size as
you have ben using on the mirror at that time.  If the grit is
larger, you need to clean up the stand and do the test again.
I'd advise against the pencil testt on finer grits due to the
grits that may be in the lead of the pencil - they don't size the
lead so that we can do that test!
I'll do the Sharpie test all the way down to the five micron
level as the ink is quite thin on a Sharpie pen )black color,
permenent ink_  so it will easily wear away.  I'll note as others
have is that the Sharpie test really isn't all that great for
this purpose as it indicates more where the grit is grinding.
Bob May
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