Universal equinoctial ring dial

Universal equinoctial ring dial for latitudes 0°-90° North. Standard dial (see related terms) except for the following details:-

It is for use in northern latitudes only. A slider moves in the grooved rim of the meridian ring and a pointer on the slider indicates the latitude. On the obverse side of the meridian ring, there is a latitude scale and the remainder is filled with a table of latitudes, primarily listing places in Britain and France. On the obverse side and the inner rim of the equinoctial ring are hour scales, while on the reverse there is another table of latitudes comprising places in England. The bridge has a date scale in months and the equinoxes are marked at 11 March and 12 September.

This dial was made by Elias Allen, the first maker of universal equinoctial ring dials. Allen was a friend of William Oughtred, their designer. It carries fewer scales than the later ones, and has no altitude quadrant unlike many other English instruments. Allen was sometimes careless in his engraving of numbers. For example, as we see here, the latitude of Cambridge was first engraved as '52 26' and then corrected to '52 16'. The sundial is signed 'Elias Allen fecit' on the obverse side of the equinoctial ring.

For more information regarding this dial please refer to the OUP & NMM catalogue, 'Sundials at Greenwich'.

Object Details

ID: AST0207
Collection: Astronomical and navigational instruments
Type: Universal equinoctial ring dial
Display location: Not on display
Creator: Allen, Elias
Date made: circa 1635
Credit: National Maritime Museum, Greenwich, London
Measurements: Overall: 4 x 64 mm

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