D8857

Universal equinoctial ring dial Long Caption: Three-ring universal equinoctial ring dial for all latitudes. A thin ring slides inside the declination ring and carries a square with pinholes at each corner. Opposite the sights square is another square with four points indicating the places where the sun's rays should fall when the instrument is correctly aligned. This dial has an unusual transversal scale for the latitudes. It has been used to allow the small latitude scale to be divided more easily into single degrees. The ring inside the declination ring replaces the more normal alidade, which could also be used for measuring altitudes as well as showing the time of day. The quality of engraving is low, particularly on the words in the latitude table. Credit line: National Maritime Museum, Greenwich, London, L Object: AST0271 Artist: unknown Date: 17th century Medium: brass Size: Overall: 4.5 x 62 mm Click here to buy a bespoke print of this image.