Nur ad-Din al-Bitruji (also spelled
Nur al-Din Ibn Ishaq Al-Betrugi and
Abu Ishâk ibn al-Bitrogi; another spelling is
al Bidrudschi) (known in the West by the
Latinized name of
Alpetragius) (died c. 1204) was an
astronomer and a
Qadi from
Al-Andalus. Despite his limited knowledge of
Ptolemy's
Almagest, al-Biṭrūjī was the first astronomer after Ptolemy to present a non-Ptolemaic astronomical system as an alternative to Ptolemy's models. Another original aspect of his system was that he proposed a physical cause of celestial motions.