SummaryThis paper reassesses the importance of the Benedictine monasteries of St Benoît of Fleury and St Mesmin of Micy (both on the outskirts of Orléans), and the Cathedral of Chartres for the early diffusion of Arabic learning concerning the astrolabe, and it relates this diffusion to that of the judicial astrology of ‘Alchandreus philosophus’ and the astronomical tables of the Preceptum canonis Ptolomei. Evidence is given for the fact that already, by the turn of the millennium, the elements were (...) in place for a corpus of a new, mathematically based, practical science of the stars, consisting of works partly of Arabic and partly of Greek inspiration. This corpus was progressively revised and inspired, in turn, further translations from Arabic, until it reached its most mature form in the mid-twelfth century. Until recently, scholarship has tended to concentrate on the cathedral schools of North-east France and Lotharingia, and the monastic schools of South Germany, and to see Gerbert d'Aurillac, the Archbishop of Reims, as the pivotal figure. While these schools were undoubtedly important in the diffusion of the new science of the stars in the eleventh century, it is argued that a key role in the initial stages of the diffusion was played by the interrelated centres of Fleury, Micy and Chartres at the beginning of the century, and Gerbert may not have contributed as much as has been believed. Additional sections are devoted to the authorities in this corpus, ‘King Ptolemy’ and ‘Alchandreus’. A reworking of the Arabic material on the construction of the astrolabe by Ascelin of Augsburg was copied into this corpus. The text has previously been known from only one manuscript; a new edition, from five manuscripts, is provided here, together with a translation and commentary. (shrink)