What field of science was the Arab scientist "Alpetragius" involved in?

Another question from belgasem goma with an apparent agenda. The description reads as though Nur ad-Din al-Bitruji's proposal was successful but it was less accurate than the prevailing Ptolemaic system, both of which put the Earth as the centre of the motion rather than the sun (as later proposed by Copernicus, but previously by Aristarchus).