Astrolabe, by Ibrahim ibn Sa'id al-Sahli, Toledo, 1068

This is a very fine instrument, inscribed in Kufi script and also featuring some Latin inscriptions in the name of the months. It is very precisely dated to the month of Shawwal 460 of the Hijra, which is the tenth lunar month in the Islamic calendar and the equivalent in the Christian calendar of August 1068.

Parts

It comprises: a mater, a rete, 6 plates, an alidade, a horse and a pin.

Throne

The throne is of the simple type decorated with four lobes per side. It is attached with a integrated base.

Ring

The ring is of the simple, squared cross-section type.

Shackle

Shackle of the omega type (i.e. Ω-shaped shackle).

Mater

The mater and limb are of one-piece construction. This instrument is unusual in that the limb is a thin plate of metal, cut to fit exactly on the mater ring and the throne. The rim is marked with a degree scale 0-360° divided every 5 degrees, subdivided every degree, and labelled in Abjad numerals every 5 degrees.

Womb

The womb features a plate for latitude 28° 20'.

Back

The back contains: four altitude scales, one for each quarter of the rim 0-90° (marked every 5 degrees); a zodiacal calendar featuring the symbols of the signs of the zodiac, divided in 30 degrees each and marked each 5 degrees on top of each sign; a Julian calendar divided in 30 degrees and marked each 5 degrees on top of each month written in both Arabic and Latin characters.

An inscription is engraved in the upper half.

The central roundel is marked with a julian calendar for a 28 year-cycle. A shadow square is engraved in the lower right quarter of the back divided in 12 fingers and marked every 2.

Rete

The rete is of the Maghrebi type with hook star pointers with inverted-heart bases, as well as "mihrab" decorative niches on the lower part of the rete. One star pointer (الحاوا) has been repaired and the name obscured. There are 4 knobs for rotation added after the rete was engraved. It features 28 stars.

Zodiac label

The zodiac on the rete features symbols for each zodiac sign and is labelled: الحمل , الثور , الجوزا , السرطان , الاسد , السنبله , الميزان , العقرب , القوس , الجدي , الدلو , الحوت.

Pin and horse

The rete is attached using a pin and a notched horse.

Alidade

Double-ended alidade. One of the sighting vanes is loose.

Plates

There are 6 plates for latitudes 21°40', 25°, 30°, 33°, 41°30', 33°30', 35°30', 36°30', 37°30', 40°, plus one blank plate and one marked with Latin numerals. The plates are engraved with almucantars for every 5 degrees, 12 unequal hours, 6 prayer lines, and are marked المشرق (east) and المغرب (west). All prayer lines (apart from the midday one which coincides with one of the unequal hours) have been added at a later stage. There are two lines for the afternoon prayer, one for beginning and one for the end of the prayer time.