Jews seem to have been particularly concerned with the formation of astronomical tables of practical utility to astronomers. Sind ben Ali (about 830) was one of the principal contributors to the tables drawn up under the patronage of the Caliph al-Mamun. No less than twelve Jews were concerned in the Tables of Toledo, drawn up about AD 1080 under the influence of Ahmad ibn Zaid, and the celebrated Alfonsine Tables were executed under the superintendence of Isaac ibn Sid, while Jews were equally concerned in the less-known tables of Peter IV of Aragon.