[ATM] Schmidt Corrector Thickness

[bobmay at nethere.com (Bob May)]

I'm working on a 6" F1.95 corrector and had two failures so far with a
thickness of 4.3mm due to the glass breaking while under tension.
Frustrating to spend the money for the good BK7 and watch it just suddenly
decide that it wants to be in two pieces rather than one.  The second piece
just broke when I walked into the room for something else and I heard a
little tink and looked at the source which was the vacuum pan and the glass
was split almost in half.  I had only another hour or so of polishing to
finish it off!
Good luck and make sure that the vacuum is under 10" or you will probably
have the same problems that I had.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net