After the early centuries, the centre of Islamic astronomy moved from Baghdad and the House of Wisdom to cities and scientists both East and West. In the East al-Biruni in Ghazni and ‘Umar Khayyam in Isfahan followed Masha'allah and Abu Ma‘shar in Baghdad. In the far West, however, in the Islamic kingdoms of southern Spain (al-Andalus), the heavenly sciences developed in a slightly different way. And this new direction was significant because, until the sixteenth century, the principal source of European knowledge about astronomy and astrology was Islamic and the principal path of transmission was by way of al-Andalus.

In 711 Arab and Berber forces under the Umayyad general Tariq ibn Zayid defeated the Visigothic king Rodrigo at the Barbate River in southern Spain and moved north. Expanding on their initial success, the Islamic forces soon controlled the entire Iberian peninsula – their advance not finally halted until 732 at Tours in southern France. After several North African governors were unable to pacify and administer the new province, an independent Spanish-Muslim state came into being. Founded by ‘Abd al-Rahman I (756–88), a grandson of the Umayyad Caliph Hasham, the Umayyad Caliphate (756–1031) in Spain had its capital in Cordoba. Over the following 250 years, especially under ‘Abd al-Rahman II (822–52) and ‘Abd al-Rahman III (912–61), a rich and prosperous Spanish-Islamic civilisation developed. A professional army provided security and a reorganised administration built irrigation canals and collected taxes. New forms of poetry and prose appeared, and new styles of architecture, exemplified by the great mosque at Cordoba, reflected the successful melding of the Arab East and the Christian West. The Spanish Umayyads patronised the works of Arab philosophers and scientists and underwrote the first translations of the Greek masters – Aristotle, Plato, Galen, Euclid, Hippocrates, and Ptolemy – from Arabic into Latin.

In Andalusia, however, as in the eastern Islamic world, unity and political stability were difficult to achieve. In the early eleventh century the Arab clans revolted, the Caliphs lost control of the central government, and the provincial governors declared their independence. The Caliphate was abolished and was followed by the rule of the ‘party kings’, a period (1030–90) characterised by independent warring states in Cordoba, Seville, Toledo, Granada, and Saragossa.