Ibn al-A'lam

'Alī ibn al-Ḥusayn Abū l-Qasim al-'Alawi al-Sharif al-Husayni ,(Arabic: ابن الأعلم الشريف الحسيني‎), (Baghdad, died 985 CE), was a 10th-century Arab astronomer and astrologer.

Very little is known about Ibn al-A'lam's life, and even his birth date has not been established by historians. Despite this fact, he seems to have been one of the most prominent astronomers of the 10th century, demonstrated by the big impact he seems to have had on both Islamic and Byzantine astronomy. From the little that is known about him, he appears to have been active in Baghdad, working under the patronage of its Buyid ruler, 'Adud al-Dawla (978–983). His Nisba "al-Alawi al-Sharif" indicates that he was a Sharif and a descendant of Ja’far al-Tayyar.[1]

Ibn al-A'lam's main work, a Zīj, was named after his patron "al-Zīj al-'Aḍudī", and was alternatively known as "al-Zīj al-Sharīfi" , or "al-Zīj al-Baghdādi". While the work itself is now lost, scholars were able to somehow reconstruct most of it based on later citations and references in Arabic, Persian, and even Greek sources.[2]

Ibn Yunus, the renowned Egyptian astronomer of the 10th century, was also a contemporary to Ibn al-A'lam, whose work he praised and regularly cited. Even after Ibn al-A'lam's death, his influence remained for at least three centuries as evidenced by the tables of Maragheh observatory which were largely based on his work and that of Ibn Yunus.[3]