Re: [ATM] Help with 50" scope

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

Andy, I hate to sound trite but I will.
Grinding and polishing out a piece of glass is pretty much the
same process no matter the size of it.  Just because it is that
big doesn't mean that itbecomes impossible to do, just taht you
need some tools to move the glass about.
The initial roughting or, as I ccall it - digging the hole -
would best be done with a diamond cutter on a swing arm.  After
you get the hole dug, a decent sized grinding tool, maybe of
about 20", would then be cast on the mirror and the mirror rough
ground for a while to smooth out the curve followed by the fine
grinding.  Finally, polishing the mirror would probably be best
done with a lap of about that same size.  Needless to say, the
first thing is make a turntable that is capable of handling the
blank and turning it at speeds up to about 1/2 rpm (maybe even
1rpm?) or so.  I'd also consider the possibility of powering the
tool spindle to increase the working speed.
I'd also plan on this taking years to do to finnish the primary
unless the guy is rich enough to pay for a full time worker to
tend to the process.  I'd also suggest that he have a building
that is tall enough inside so that the mirror can be tested
without having to lift it off of the grinding table.  This will
preclude any spills of the glass that would be rather nasty.  For
an F3 primayy this would be about 25' for the ROC and about
another 7' or so for the other stuff.  Tilting the grinding table
by 45 degrees can bring tthat height down to 20' wich will not be
hard to find.
Bive me enough inducements and I'd like to try the project but
that would be a permenant move to that area.
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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