Interest in astronomy has been a constant feature of Arabic culture since the end of the second century AH (eighth century AD), and it is the quantity of study which strikes us first when we begin exploring this subject: the number of scientists who have worked on theoretical astronomy, the number of treatises which have been written in this field, the number of private or public observatories which have been successively active and the number of precise observations recorded there between the ninth and the fifteenth centuries.
This chapter is exclusively concerned with astronomy as an exact science, without considering the question of astrology. In fact, although the same authors sometimes wrote treatises in both disciplines, they never mixed purely astronomical reasoning and purely astrological reasoning in the same book and in most cases the titles of the works indicate unambiguously whether their contents relate to one discipline or the other.
The science of astronomy is chiefly defined by two terms: ‛ilm al-falak, or ‘science of the celestial orb’, and ‛ilm al-hay’a, or ‘science of the structure (of the universe)’; the second term can be translated in many cases as ‘cosmography’. In addition, many astronomical works are identified by the word zīj, a term of Persian origin corresponding to the Greek kanôn; in its proper sense it denotes collections of tables of motion for the stars, introduced by explanatory diagrams which enable their compilation; but it is also often used as a generic term for major astronomical treatises which include tables. 1
The astronomical term which is generally used to refer to the stars is kawkab, kawākib, while a word of similar meaning, najm, nujūm, has a more astrological connotation, and astrology is described with the aid of expressions based on the latter term: ‛ilm aḥkām al-nujūm, ṣinā‛at al-nujūm, tanjīm…; 2 however, ‛ilm al-nujūm, ‘the science of the stars’, can