ReflectingTelescope_017.jpg
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Summary
| Description | Largest disk of optical glass created in the United States as of 1928. The mold for this disk was specifically designed for this purpose and was at the same time a carefully insulated annealing furnace provided with electrical heating elements for controlling the temperatures during cooling. The glass was poured at 2400 degrees Fahrenheit. Eight months were required for cooling and annealing. The disk weighed about 4,000 pounds, was 11 inches thick, and made from borosilicate crown glass. It was intended for use at the Perkins Observatory of Delaware, Ohio. | |||
| Source | National Institute of Standards and Technology | |||
| Author | National Institute of Standards and Technology | |||
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Permission
( Reusing this file ) |
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Licensing
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This image is in the
public domain
in the United States because it is a
work of the United States Federal Government
, specifically an employee of the
National Institute of Standards and Technology
, under the terms of
Title 17, Chapter 1, Section 105 of the
US Code
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