Re: [ATM] Controlling focal length

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

Don't worry about the focal length of the two mirrors being the
same at this point.  They are much closer than you can eaisly
measure  The important thing is to keep the two mirrors swapping
on the tool to keep their ROCs the same.  When they are both
preforming the same with the Sharpie test then you know that they
are basically the same.  When you get to the 12 or so micron
statge, that is when you really want to start swapping the
mirrors during a wet.  When you polish, you want to spend no more
than 10 or 15 minutes at a time with either mirror to insure that
the pittch lap isn't changing curvature.  Do all of that and you
won't be able to measure the diffeerence in the ROC of the two
mirrors.   Been there and done that with a set of 8" mirrors and
I could put either mirror on the test stand and do a Foucualt
test and get the same ROC with the other mirror.
Bob May
bobmay at nethere.com
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http: slash /bobmay dot astronomy.net
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Thank you for your understanding!

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