 He built an observatory in 1428 and produced the first original star map since Ptolemy, which corrected the position of many stars and included many new ones.Some of the principles of astrology were refuted by several medieval Islamic astronomers such as Al-Farabi (Alpharabius), Ibn al-Haytham (Alhazen), Avicenna, Abu Rayhan al-Biruni and Averroes.Their reasons for refuting astrology were often due to both scientific (the methods used by astrologers being conjectural rather than empirical) and religious (conflicts with orthodox Islamic scholars) reasons.