Diptych dial

Diptych dial for latitude 49° North. This miniature rectangular dial consists of two leaves that fold flat when not in use. Leaf I is made completely of ivory and leaf II has a wooden core. Leaf Ia displays a standard lunar volvelle (see related terms) except the brass rotatable disc is missing. The hour scale is marked in red and the lunar-age scale in black. The leaf has a single-lined border and red trefoil decorations in the corners. Leaf Ib features the vertical dial with hour-lines in blue radiating from a double semicircle inside which are two red snowflake motifs. The leaf has a single-lined border.

Leaf IIa is as standard except the hour numbers are in black and the hour-lines are in blue. A string gnomon is attached between the inner surfaces of the two leaves. The compass needle is blued, in the form of an arrow and covered by a glass plate held in place by copper wire. There are no dials for Babylonian and Italian hours. Two red snowflake motifs adorn the base of the gnomon. A brass pin for keeping the two leaves aligned when the dial is closed is at the bottom right of the leaf. Leaf IIb is bare apart from a very faint maker's mark - a hand - that belongs to Leonhard Andreas Karner. The leaves have a brass hook fastener, which is broken and a copper hook for holding the dial open. This instrument is very similar to AST0285.

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

Object Details

ID: AST0414
Collection: Astronomical and navigational instruments
Type: Diptych dial
Display location: Not on display
Creator: Karner, Leonhard Andreas
Date made: Early to mid 18th century
Credit: National Maritime Museum, Greenwich, London, Caird Collection
Measurements: Overall: 12 x 34 x 44 mm

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