This instrument is a reproduction based on two Gunter type quadrants (E. Gunter, 1581-1626), made in the mid-18th century. Both originals, by unknown English authors, are in the National Maritime Museum in Greenwich, London.
On the one hand, the instrument has a local altitude quadrant with a system of pinulas to take the altitude of the sun, complemented by the inclusion of a thread with a plumb line and a sliding bead. It contains a series of scales, some of them based on the stereographic projection, which allow to find the time easily and to solve many problems related to the position of the sun.
On its back there is a nocturnal whose purpose was to provide orientation for ancient navigators who, by memorising the position of the brightest circumpolar stars, could help them in their night-time observations.
