Re: [ATM] Chabot Recollection

[John Lynch <john_lynch2007@yahoo.com>]

It is my understanding that the 200" group (headed by
Hale) went to GE to investigate the use of fused
quartz, which was a new technology that had not yet
been mastered.  After numerous unsuccessful attempts,
and hundreds of thousands of dollars later, Hale went
to Corning for the Pyrex option, which was used as an
alternative to fused quartz because of its
availability and acceptable properties.  In the book
"The Perfect Machine," Ronald Florence indicates that
Pyrex had been around for awhile and was used for the
manufacture of custard cups.  

John Lynch

--- Stan Truitt <s.truitt@hawaiiantel.net> wrote:

> Aloha Group!
> 
> 
> >Interesting, homebrew in 1955. Not everyone
> aluminized at that time.
> >Did you use pyrex?
> Yes, it was a Corning blank with a tapered 
> periphery, and on the back side it had a raised 
> rim about 9mm wide and 3mm high. The area inside 
> the rim was not flat and had a raised word 
> "Corning" just inside the rim. The entire surface 
> had a fire polished look and was transparent, as 
> opposed to the merely translucent Pyrex blanks 
> seen today. It was especially entertaining, being 
> able to view the surface of the lap and the rouge 
> bubbling in the channels, while polishing.
> >
> >I get the idea that plate glass has been used
> >extensively in the past and not real sure how the
> practice of
> >using pyrex developed.
> I understand that Pyrex telescope mirror blanks 
> became readily available just after WWII.
> 
> 
> >Come to think of it, I think it was the Lick 
> >mirror that was made from wine bottles.
> No, the 120 inch Lick mirror was cast in Pyrex as 
> practice for the 200 inch pourings, and was 
> intended to be a test flat if needed for testing 
> the 200 inch.  One reason the 120 inch has such a 
> large focal ratio is that the face sheet web 
> thickness of the blank was too thin for a deep 
> sagitta.
> << The heart of the Shane telescope, the 120-inch 
> primary mirror, was originally a glass test blank 
> cast in Corning Labs for the Palomar Observatory 
> 200-inch reflector. Pyrex, the well known 
> "cooking glass," was in fact invented for these 
> telescope mirrors. CalTech generously sold the 
> 120-inch blank to Lick Observatory at a nominal 
> cost of $50,000.>>
> 
> The 100 inch Hooker blank was cast from bottle 
> glass material, not actual bottles, by St. Gobain 
> in France, in 1905.
> http://www.mtwilson.edu/his/art/g1a4.php
> 
> 
> Clear warm skies,
> 
> Stan Truitt     20° 51'  N,  156° 22'  W   511 M 
> MSL
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> ATM mailing list http://www.atmlist.net/
> 



 
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