He was involved in the measurement of the diameter of the Earth together with a team of scientists under the patronage of al-Ma'mūn in Baghdad. His textbook Elements of astronomy on the celestial motions, written about 833, was a competent descriptive summary of Ptolemy's Almagest. It was translated into Latin in the twelfth century and remained very popular in Europe until the time of Regiomontanus. Dante Alighieri's knowledge of Ptolemaic astronomy, which is evident in his Divina Commedia as well as other works such as the Convivio, seems to have been drawn from his reading of Alfraganus. In the seventeenth century the Dutch orientalist Jacob Golius published the Arabic text on the basis of a manuscript he had acquired in the Near East, with a new Latin translation and extensive notes.

Later he moved to Cairo, where he composed a treatise on the astrolabe around 856. There he also supervised the construction of the large Nilometer on the island of al-Rawda (in Old Cairo) in the year 861.