a celebrated Arabian astronomer of the ninth century, born at Balikh, in Khorassan. He had reached the age of 47 before he entered on the studies to which he owes his fame. His principal works are An Introduction to Astronomy, and the Book of Conjunction, both published in a Latin translation at Augsburg, in 1489, and again at Venice in 1515; and a work On the Revolution of the Years is also attributed to him.