Dieppe magnetic azimuth dial for 50° North (0°-80° North for equinoctial dial). Standard Dieppe magnetic azimuth dial (see related terms) except for the following details:-

The dial is split into four leaves. Leaf Ia carries an equinoctial dial and a polar dial; the pin gnomon for use with both these dials is missing. Leaf Ib consists of a lunar volvelle made of a pewter-brass alloy. Leaf IIa has a horizontal dial as well as the magnetic azimuth dial. The hour scale for the horizontal dial surrounds the compass well, and attached between the two leaves is a red string gnomon for latitude 48°. The printed compass card has a rose showing 16 points and carries a radial table of latitudes for various places in Europe, North and South America, the Philippines, New Guinea and India. Leaf IIb has a date scale and a perpetual calendar on a pewter-brass volvelle. The dial is signed 'Ephraim Senecal ADieppe Fecit'.

The presence of the horizontal dial scale around the compass well means that this dial can be used simply by turning the instrument until both the horizontal dial and the magnetic azimuth dial give the same time. There is wheatsheaf decoration on the back of the dial, which is unusual for a French instrument. The table of latitudes is the same as that in AST0327, although the values given for the latitudes are rather different. Another dial by Ephraim Senecal is in the Whipple Museum (accession no. Wh: 1692).

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