Airy Transit Circle eyepiece, Greenwich Observatory, London, UK. A transit circle is used to observe the transit of stars across a fixed line. This on

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Airy Transit Circle eyepiece, Greenwich Observatory, London, UK. A transit circle is used to observe the transit of stars across a fixed line. This one, famous for its use in setting Greenwich Mean Time (GMT), was proposed by the British astronomer George Biddell Airy (1801-1892). Construction was by the engineering firm Ransomes and May of Ipswich. The first observations were taken on 4 January 1851, and the instrument was in regular use until 1954. It is now on display in the observatory which was turned into a museum. Steps and bannisters are seen either side of the eyepiece, enabling the operator to access the movement controls.

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Size: 4284px × 4169px
Photo credit: © ROYAL ASTRONOMICAL SOCIETY/SCIENCE PHOTO LIBRARY / Alamy / Afripics
License: Licensed
Model Released: No

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