This instrument is a reproduction based on two Gunter quadrants (E. Gunter, 1581-1626), made in the middle of the eighteenth century. Both originals, of unknown English authors, are in the National Maritime Museum of Greenwich, London. On the one hand the instrument has a local quadrant of height equipped with a system of pinsules to take the height of the sun that is complemented with the inclusion of a thread with a plummet and a sliding bead. It contains a series of scales, some of them based on the stereographic projection, that allow to find the time with ease and to solve many problems related to the position of the sun.
On its back appears a nocturnal whose purpose was of orientation for the old navigators who, in memorizing the position of the brightest circumpolar stars, could be aided in their nocturnal observations. |