Horizontal sun and moon pedestal dial for latitude 51° 30' North. This dial has an octagonal dial-plate with an hour-circle and minute-circle. The hour-lines radiate from a circle centred at the base of the style. A highly decorated 16-point compass rose is centred on the northern end of the triangular fretwork gnomon. Centred at the base of the style is a further hour-circle and lunar-age circle. Engraved in the hour-circle is the maker’s signature, ‘Elias Allen fecit’.

This pedestal dial has no volvelle for adjusting the instrument for lunar time. Instead, the maker has included an explanation (in a square at the bottom edge of the gnomon) of how the lunar time can be adjusted by an arithmetical calculation to give the solar time: ‘This circle deuided into 29½ is for the age of the moone, the circle without is for the houres of the daie and night The houre which is ouer the age of the moone sheweth the time when the moone cometh to the south when the moone shineth the houre whereon the shadow of the style falleth will shew the time of the moones distance from the south and consequently the houre of the night’.

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