Inventory no. 15598 - Former Display Label
Turkish ASTROLABE-QUADRANT
1094 A. H. = 1682-3 A. D.
Lacquered wood, with original case of velvet decorated with metal wire and lined with silk. Signed, 'Designed by Ahmad al-Ayyûbî', and dated, '1094' [A. H. = 1682-3 A. D.].
One side of this instrument bears a Prophatius-type astrolabe-quadrant, a reduction to a quarter of a circle of the essential lines of the stereographic projection on the rete and plates of a conventional astrolabe. The astrolabe quadrant was first described by the Judaeo-Provençal mathematician, astronomer, and zoologist, Jacob ben Mahir ibn Tibbon, known as Prophatius Judaeus (c.1236-c.1304). Above the astrolabe-quadrant, there is a horary quadrant which was used, in conjunction with a sliding-bead on a plumb-line and bob (now missing), for time-telling (in unequal, or 'planetary' hours); the two projections on one of the radii served as sights.
The other side bears a sinecal quadrant which is divided sexagesimally and enables the sines and cosines, of the angles marked along the arc, to be ascertained from the scales along the radii. Super-imposed on the network of lines are arcs known as the 'arc of the obliquity of the ecliptic' and arcs of sines and 'versed sines'.
[60-70]
Purchased in 1960
Other narratives:
- Instruments of Ottoman Turkey
- Special Exhibition Label: 'Al-Mizan: Sciences and Arts in the Islamic World' (26/10/2010 - 20/03/2011)