Lunar mansions
The 'lunar mansions' are the constellations through which the moon passes in its cycle of motion around the earth and they are used, especially in astrology, as a way of dividing up the celestial sphere. The back of this astrolabe has a scale of the 28 mansions of the moon and each one is given a pictorial representation, as are the more familiar signs of the zodiac.
Astrolabe, by Abd al-Karim al-Misri, Syro-Egyptian, 1227/8 (Inv. 37148)