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Image: ReflectingTelescope 017

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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.
Title: ReflectingTelescope 017
Credit: National Institute of Standards and Technology
Author: National Institute of Standards and Technology
Permission: 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.
Usage Terms: Public domain
License: Public domain
Attribution Required?: No

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