Re: ATM [Hist.][Long] Schmidt corrector plates in old televisions/Slumping Schmidt correctors

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

Actually the process that Meade and Celestron is probably a bit better as it
doesn't need to make the glass warm enough to change it's shape.
What they do is to draw the vacuum just like Schmidt developed into a
precision mold and it takes minutes to polish in the curve on a polishting
machine while the glass is bent.  Then again, the amount of material that
needs to be removed for those scopes isn't all that much.
Anytime you heat glass and get it to slump, you have to deal with the
problems of stress that remains in the glass from the movement and thus, you
have to spend some time annealing the glass afterwords.
Bob May
http://nav.to/bobmay
bobmay@nethere.com