Astrolabe quadrant

Europe, 14th century AD

One of only seven surviving medieval European instruments of this type

An astrolabe quadrant basically consists of the markings of an astrolabe folded twice. This type of instrument was known in Europe from the fourteenth century onwards.

The instruments have the ususal markings of an astrolabe, but the engraving is often not very precise. On this example, the lunar volvelle (a rotating disc on the back) has been left unfinished and the calendrical scales on the back of the quadrant are therefore useless. Also, a plumb bob attached to the tip of the instrument, that would be needed to use the astrolabic markings on the front, is now missing.

E. Dekker, 'An unrecorded medieval astrolabe quadrant from c. 1300', Annals of Science-1, 52 (1995)