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Conical Vs Thin Mirror Blanks

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Posted by William Woturski on November 21, 2000 03:08:19 UTC

I am planning to build a 24". I have
some questions that perhaps someone can answer. Back in 1983' in "Sky and
Telescope" I read an article on a 24" scope built with a Pyrex Conical
Mirror. I have not been able to find any further information on
whether
these make good mirrors or do they suffer from thermal equilibrium
problems due to this mirror's 3" thick center which tapers to 1/2" at
the edge. Are thinner Pyrex (~2") mirrors better because they
equilibrate faster? Are slumped mirrors better than flat and how do
you
mount the slumped one in a cell. Does one use a standard multi-point
Dobsonian cell? In my 98' Newport Catalog they do sell conical as well
as the standard flat and they will slump the thin ones for you as well.

Also is anyone planning a large buy of for fine annealed blanks in the 16-30 inch
range and glass tools from 8" to 30".

I would appreciate any information you can give me. Thank you?
Bill

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