Re: [ATM] Corrector plate thickness

[Dominic-Luc Webb <dlwebb@canit.se>]

On Sat, 17 Nov 2007, Joe Johnson wrote:

> Hi,  I'm going to make a Schmidt-cassegrain and have a question
> for anyone with experience.  Newport Glass sells corrector plates but
> they seem to be on the thin side: 3/8" thick for a 12.25" diameter
> disk.  Is this thick enough to hold the secondary without flexing?

Many things can be said about the secondary, but to start with, my
math tells me this is a bit over 9.5 mm thick, which sounds like a
bit more than you need for success. The equations for the corrector
curve includes parameters for not only refractive index and diameter,
but also thickness. I have not looked at this particular Schmidt
variant, but would guess that like with other designs, it is
desirable to have the secondary as a separate piece of glass that
may or may not be hanging from the corrector.

Dominic

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