Works by the scholars of the mid-13th century observatory at Marāgha were sources of inspiration for Ibn al-Shāṭir's own non-Ptolemaic planetary models. Later astronomers in Damascus and Cairo, prepared commentaries on, and new versions of Ibn al-Shāṭir’s zīj. In its original form and in various recensions, this work was used in both cities for several centuries. His principal treatises on instruments remained popular for several centuries in Syria, Egypt, and Turkey. Ibn al-Shāṭir’s models are mathematically identical to those of Copernicus raising the question of a possible transmission of his planetary theory to Europe. [D. King]