Re: [ATM] ritchey cretians

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

Your goals are not that of some little size!  a four foot mirror
isn't something to just whip together in a few weeks but rather a
real project of some size.  Nothing you are going to do is going
to be the same as with a smaller mirror except the sound of the
mirrors being ground.  You're going to be wanting machines to
grind and polish the blank just as a start and then machines to
lift and position the glass on the testing stand.  Don't even
think of doing any of that work by hand as you'll drop the glass
at the first opportunity and that will mean a fair bit of money
out the window.  Even hogging out the glass in the beginning will
be a fairly major project!  Diamond tooling is the wya to go
there as you'll be spending that much on grit without any
trouble, even if you get sandblasting grit for the first few
grits.
As to speed, sit down and see what you really need for a primary
and go from there.  There is generally no need to go to something
really fast as the performance of a really fast system won't be
that good and the surfaces will definitely need hand work after
you're mostly done to perfect the shapes needed.
Good luck with the project!  Up at Mt. Laguna the large scope is
a 48" Cassegrain camera and when I was last up there, their
project was looking at galaxies for novas and supernovas in order
to gain a better understanding of them.
Bob May
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