Re: [ATM] practical limits of 1 inch mirror

["Thomas Janstrom" <thomas@moiler.com>]

With extreme care you should be able to get up to about the 20" mark, but at
20:1 you will be pushing the envelope, not as much as some (there is talk of
doing a 36" out of 5/16" plate!!!! As a side note it might be possible to
just pull a mirror like that to the required curve, so long as you wanted a
mirror in the F10 range!), but none the less not an easy task.

If you were to stick with a ratio not higher than 15:1 then things are MUCH
easier, and a 15" scope has quite the light grasp! That said it comes back
to supporting the blank really well during grinding and polishing, and an
equally good support system when in use (might you not use your final mirror
cell to grind and polish the mirror in?).

Anyway, that's my $0.02.

Cheers, Thomas.
 

-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
David Weinshenker
Sent: Wednesday, 2 January 2008 7:07 AM
To: ATM List
Subject: [ATM] practical limits of 1 inch mirror

I note that Schott advertises "Borofloat" plate glass (fairly
similar in characteristics to Pyrex, but made by a "micro-float"
process) in large sheets - but only up to 1 inch thick.

Other than that, it looks like it would be excellent telescope-mirror
glass (and should certainly work quite nicely for mirrors at least
in the 6 to 10 inch range).

To what extent are larger diameter mirrors practical with 1 inch glass?

-dave w
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