 Astrological prognostications nevertheless required a fair amount of exact scientific expertise and the quest for such knowledge within this era helped to provide the incentive for the study and development of astronomy.Medieval Islamic astrology and astronomy continued Hellenistic and Roman era traditions based on Ptolemy's "Almagest".Centres of learning in medicine and astronomy/astrology were set up in Baghdad and Damascus, and the Caliph Al-Mansur of Baghdad established a major observatory and library in the city, making it the world's astronomical centre.