Diptych dial

Diptych dial for latitudes 42°-51° North. This dial consists of two leaves that fold flat when not in use. Leaf Ia carries a standard windrose (see related terms). Leaf Ib is as standard except the dial at the top shows the length of the day and the planetary hours. Holes for the string gnomon (missing) are labelled '51', '48', '45' and '42'. Below is a table of latitudes for places in Europe. There is no vertical dial. Leaf IIa is as standard except there are four concentric hour scales (marked '42', '45', '48' and '51' outwards) for the horizontal dial. A string gnomon for use with this dial is attached between the inner surfaces of the two leaves and is adjustable for various latitudes.

The compass is offset 4° East of North to allow for magnetic variation; there is also a later indication of magnetic variation marked at 20° West of North. The dials for Italian and Babylonian hours are marked 'I' and 'S' respectively. Leaf IIb features a standard lunar volvelle surrounded by two circular epact tables: the inner one for Gregorian epacts, the outer for Julian epacts. The dial is signed 'CONRAD KARNER'. The foliate designs on this instrument are similar to those of Michael Lesel (AST0438), who was related to the Karner family by marriage - thus similarities between the two are hardly surprising. There are some errors in the epact tables.

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

Object Details

ID: AST0155
Collection: Astronomical and navigational instruments
Type: Diptych dial
Display location: Not on display
Creator: Karner, Conrad
Date made: circa 1629
Credit: National Maritime Museum, Greenwich, London. Caird Fund.
Measurements: Overall: 12 x 63 x 94 mm

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