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Thin Plate Glass Mirror Question...

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Posted by David Gede on January 6, 2002 17:36:05 UTC

Please be gentle, I am very new to this topic. I have been reading several threads in this newsgroup about mirror grinding. I never thought about it before but with all the encourgement found here, I might try it.

Over the last several weeks I have been reading all that I can get my hands on about the type of glass to use. Most recommend using pyrex. I would like to, but my goal is to work up to a 16" mirror, and the cost becomes a little too much.

In an earlier thread, I found a reference to a gentleman selling surplus army glass cut into rounds. The glass looks to be of good quality but is only 7/8" thick. The price is certainly right and he provides supplies and insturctions for grinding, polishing and figuring.

Now here is the question. I live in Maryland and deal with 90 degrees in the summer and routinely deal with 20 degrees in the winter. What effects can I expect with a very thin plate glass mirror, in a truss tube newtonian? Will I simply struggle on any night that the temperature is not perfect?

Just as a clarification, I am going to start with a 6" or 8" blank to make sure I can (and want to do my 16 myself).

Any help or direction would be greatly appreciated.
Dave Gede

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