The astrolabe was described for the first time around 550 in Alexandria but its improvement is essentially the work of the Muslim astronomers. In the tenth century of our calendar an enthusiastic theorist listed about 1000 different uses of this truly universal instrument, in the etymological meaning of 'universal'.
The use of the astrolabe extends of course to all the Muslim world as far as Spain, but the most advanced theoretical and practical treatises remain the work of the astronomers of the Middle East.
The ibn al-Saffar brothers worked in Cordoba at the beginning of the 5th century of the Hegira. Ahmed is a very important teacher whose writings will be used for four centuries. Muhammad makes the instruments.
Three astrolabes signed by Muhammad ibn al-Saffar are known. The earliest, dated 411AH corresponding to 1020/1021 in our calendar, is estimated £ 300K for sale by Sotheby's in London on April 26, lot 170. It is a big piece 19 cm overall including the suspension loop.
This astrolabe is complete but not entirely original, for a valid reason. Indeed the rete which simulates the map of the sky becomes obsolete after a few decades due to the precession of the equinoxes. The ancient users were aware of this phenomenon and the rete of this instrument was changed in Ottoman Turkey. The position of one of its star pointers suggests a date around 1550 of our calendar for this replacement part.
The mater is the rear side of the instrument. This one is set to the 66° latitude corresponding to the longest day time known by the astronomers in the Antiquity. Six original double-sided removable plates are joined with the indication of latitudes and cities, inviting for a fabulous journey into the medieval Muslim world. From South to North : Yemen, Mecca, Medina, Cairo, Qairawan, Damascus, Malaga, Cordoba, Toledo, Zaragoza.
The link in Sotheby's tweet below leads to photos of this instrument after disassembly to explain the mater, the loop, the plates, the alidade or sight rule and the rede.
SOLD for £ 500K before fees