Universal equinoctial ring dial

Three-ring universal equinoctial ring dial for all latitudes. Standard dial (see related terms) except for the following details:-

The dial has bracket slides in grooves in the outer edge of the meridian ring and an engraved arrow on the bracket acts as a latitude indicator. The inner rim of the equinoctial ring has an hour scale while the obverse side of the declination ring has the zodiac scale around the North Pole and a date scale around the South Pole. The ring has crossed supporting struts, mounted on which is an alidade with pointers that move over the declination scale to indicate the position of the sun in the ecliptic. The alidade sights, folding flat when not in use, each have three pinholes: two above and one below. This allows the time to be read at noon, because not all of them are obscured at once by the meridian ring. There is a lock for the equinoctial ring at the South point of the meridian ring.

The obverse side of the meridian ring is signed 'N Bion AParis 49 Deg:' and also displays a table of latitudes consisting of a fairly standard list of European towns and cities. The reverse side of the equinoctial ring contains a table almost completely confined to places in Spain or Spanish colonies, indicating that the original owner was probably Spanish. This is a very fine example of the three-ring form of the universal equinoctial ring dial and can be used for taking stellar altitudes, as indicated on the alidade support struts.

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

Object Details

ID: AST0310
Collection: Astronomical and navigational instruments
Type: Universal equinoctial ring dial
Display location: Display - ROG
Creator: Bion, Nicolas
Date made: 1685-1715
Credit: National Maritime Museum, Greenwich, London, Caird Collection
Measurements: Overall: 8 x 141 mm

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