The ʿAbbāsid Caliph Maʾmūn (r. 813-33), the son of Hārūn al‐Rashīd (r. 786-809), was known for his patronage of the mathematical sciences. He sponsored two sets of astronomical observations (one in Baghdad, the other in Damascus) with the intent of producing more precise parameters. The astronomical handbook with tables, "al-Zīj al-Maʾmūnī al-mumtaḥān," was dedicated to him (see Yaḥyā ibn Abī Manṣūr).