Mechanical equinoctial dial for latitudes 30°-60° North. This dial has a rectangular base with a semicircular extension. Screwed to the base is a latitude arc that has a second part behind it attached to the underside of the hour-plate. The hour-plate is held to the base-plate at the North end by a hinged plate and carries an hour-circle. Pivoted to the centre of the hour-circle is a rotatable disc which can be locked in place by means of a wing nut on the underside of the hour-plate. The disc has an index arm with two shaped pointers that move over the hour-circle.

Screwed to the index arm in a vertical plane is an arced declination scale, which also functions as a support for the pivoted alidade. The declination scale is marked on one side by the date and on the other by a zodiacal scale, and it has a slit down the centre along its length. The alidade is on the zodiacal scale side and it carries two shaped pinhole sights. The end that moves over the declination scale has a pointer, which indicates the position of the sun in the ecliptic. The slit in the declination scale allows the date to be read at the same time.

This instrument is made according to the same design as a mechanical dial but is not one, since it does not possess a minute-circle with a hand that is moved by the movement of the alidade. It is signed 'Franz Antoni Knittl' on the hinge of the hour-plate.

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