Universal equinoctial dial for latitudes 30°-90° North. The base-plate is in the form of an irregular octagon and is engraved with zodiacal symbols. It is surmounted by a second horizontal plate with three brass levelling screws. This plate is engraved with the maker’s signature, ‘Le febvre AParis’, and a table of latitudes in two columns listing places in Europe. Attached to this plate are the hour-circle and latitude arc. The hour-circle is pivoted within a hinged semicircular arc support. A pivoted strut across its East-West diameter carries a perpendicular scale for setting the gnomon with respect to the sun’s declination. The latitude arc is hinged to the edge of the upper base-plate. The plumb bob consists of a steel plummet and a brass bob.

This dial has no need for a compass because when the pinhole gnomon is set for the solar declination it will only cast light on the hour scale when the instrument is oriented in the correct direction. Thus it more closely resembles the self-orienting universal equinoctial ring dials than the standard universal equinoctial dials, which require a compass. The advantage of this type of dial is that there is no possibility of error due to the magnetic variation not being known accurately. Although this arrangement is unusual for a universal equinoctial dial, a similar design is seen in AST0333, and the crescent dials in the Museum’s collection (see AST0503, AST0352 and AST0373) work on the same principal.

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