Diptych dial

Diptych dial for latitudes 42°-54° North. This rectangular ivory dial consists of two leaves that fold flat when not in use. Inscribed at the top of leaf Ia is an instruction concerning the dial that notes that the hole '54' is required for England, Scotland and various places in Scandinavia. The rest of the leaf is occupied by five concentric horizontal dials. The gnomon is missing. Places are also listed for latitude 42°. Leaf Ib is as standard (see related terms) except the pin gnomon is missing and there are no hour-lines for Babylonian or Italian hours. There is a vertical dial and a continuation of the explanations describing places for latitudes 51° and 48°.

Leaf IIa is as standard except the compass is below the horizontal dial. Within the hour scale are nine concentric circular scales for Italian hours and a string gnomon is attached between the two leaves. The cardinal points of the compass are named in German and Latin and magnetic north is marked at 6° East of North. The maker's mark of a snake appears in both bottom corners and '1580' is inscribed above each. Leaf IIb carries a lunar volvelle. A further explanation fills the rest of the leaf describing places for latitudes 45° and 42°.

Hans Ducher often included explanations of the use of the diptych dial on the instruments themselves (see Lloyd (1992), p. 48, no. 1; Gouk (1988) catalogue nos 2, 17, 19, 27, 50 and 52). The instructions on this instrument are particularly full. On leaf Ib, the dial is signed 'HANS DVCHER ZV NVRNBERG'.

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

Object Details

ID: AST0494
Collection: Astronomical and navigational instruments
Type: Diptych dial
Display location: Not on display
Creator: Ducher, Hans
Date made: 1580
Credit: National Maritime Museum, Greenwich, London, Caird Collection
Measurements: Overall: 13 x 75 x 106 mm

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