Re: [ATM] Chabot Recollection

[Stan Truitt <s.truitt@hawaiiantel.net>]

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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