Al Urdi (d. 1266) from Aleppo, is famed for his Kitab Al-Hayah (A Book on astronomy). He was the first astronomer associated with Maragha to initiate constructing planetary models. He built astronomical instruments and wrote The instruments of the observatory of Maragha. Al-Urdi is also an architect and engineer who began his technical career in Syria, doing some engineering (Hydraulic) work in Damascus and constructed an astronomical instrument for the King of Hims Al-Mansur Ibrahim (ruler of Hims 1239-45). Following the invasion of Syria by the Mongols in 1259-60, Al-Urdi was taken to Maragha to work in the observatory there. Al-Urdi's description of the instruments at Maragha shows that the Muslims realised the need for precise instruments and methods; and much importance was attached to such matters as the stability and correctness of the instruments and of each of their parts. Al-Urdi also wrote two other treatises:
- Risala fi amal Al-Kura (Construction of the perfect sphere)
- On the Determination of the distance between the centre of the sun and the apogee.
- Astronomical treatises and a treatise on Ptolemaic astronomy are also ascribed to him.