6-inch telescope mirror blank; Corning Pyrex borosilicate glass For Sale
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6-inch telescope mirror blank; Corning Pyrex borosilicate glass:
$39.95
6-inch Pyrex glass blank; partially worked
For your consideration is this 6-inch glass blank made of Corning Pyrex (code 7740) borosilicate glass. As you may know, Pyrex is no longer made, but is still desirable due to its low thermal expansion coefficient (3.25 x 10-6 per C), which is superior to that of plate glass.
This blank probably started life as an 8-inch United lens molded blank, but has been worked on all surfaces. The perimeter has been machine-ground to a diameter of 6.035\". One face is fine-ground flat, the other face has been fine-ground to a steep concave sphere of 16.62\" radius. The central sag can be seen in the 4th picture. So if you want to make a short-focus, very-fast optic, you\'re already there!
The chamfer is modest and free of chips; the flat -side chamfer has one small stoned cavity approx 1/8-inch wide. Edge thickness is 0.98\". Weight is 1 lbs, 14.8 ounces.
The item will be well packaged for safe shipment. Estimated shipping weight is 3-4 lbs. Local pick-up is allowed.
Thanks for looking.
