Abstract
WHEN the Royal Observatory moves from Greenwich to Herstmonceux, the Airy transit circle, which was installed in 1851 and which marks the zero meridian of longitude, will be left at Greenwich, along with a collection of older instruments dating back to the time of Halley. They will form an interesting historical exhibit. The Airy instrument has reached the end of its useful life ; the objective has twice been repolished and refigured and is too thin for a further repolishing which is now needed ; many of the circle graduations have been almost obliterated by repeated cleaning; the instrument is nonreversible and obsolete in various respects. The Observatory possesses a modern reversible 7-in. transit circle, made by Cooke, Troughton and Simms, and installed in 1936, which is required primarily for fundamental observations. A second transit circle is needed for differential zone observations.
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Transit Circle for the Royal Observatory, Greenwich. Nature 161, 271 (1948). https://doi.org/10.1038/161271a0
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DOI: https://doi.org/10.1038/161271a0