An Andalusian tradition of zījes seems to have been predominant in the Maghrib due to the popularity of the zīj of Ibn Is[hdotu]āq al-Tūnisī and derived texts compiled in the fourteenth century. This tradition computed sidereal planetary longitudes and allowed the calculation of tropical longitudes by using trepidation tables based on models designed in al-Andalus by Abū Is[hdotu]āq ibn al-Zarqālluh. This tradition also used Ibn al-Zarqālluh's model to calculate the obliquity of the ecliptic, which implied that this angle had a (...) cyclical period of oscillation between a maximum of 23;53° and a minimum of 23;33°: after reaching this minimum value the obliquity of the ecliptic was bound to increase. This paper argues that some new Maghribi sources give information on observations made in the Maghrib in the fourteenth and beginning of the fifteenth centuries that imply that precession had increased beyond the limits allowed by the Zarqāllian trepidation theory, while the obliquity of the ecliptic had diminished below the level accepted by astronomers who followed Ibn al-Zarqālluh. This explains the introduction in the Maghrib of Eastern zījes, which computed directly tropical longitudes and did not accept the cyclical variation of the obliquity. Information about observations of dawn and twilight made both in Egypt and in the Maghrib in the fourteenth and fifteenth centuries is also presented. (shrink)

In 1953 Marshall Clagett presented a preliminary scheme of the medieval Latin versions of Euclid'sElements. Since then a considerable body of these texts has become available in critical editions, thanks to Clagett's labours on the Archimedean tradition and H. L. L. Busard's work on the Euclidean versions. Further, Busard, M. Folkerts, R. Lorch and C. Burnett have scrutinized the pivotal ‘second’ version of Adelard of Bath, and have thereby exposed a diversity of text forms that spells real complications for the (...) effort to establish its provenance and use. In his recent overview of the medieval Euclidean tradition, Folkerts displays not only how these studies have filled out and expanded upon Clagett's initial framework, but also how they have compelled rethinking of some basic issues, such as on the source relations and authorship of the various versions. (shrink)

The ArgumentLevi ben Gerson, also known as Gersonides or Leo de Balneolis, was one of the most original Jewish thinkers of the Middle Ages, and he wrote on logic, philosophy, biblical exegesis, mathematics, and astronomy. During the last years of his life he maintained relations with the papal court of Clement VI (1342–52) at Avignon, and collaborated in the translation into Latin of hisSefer Tekhuna(Book of Astronomy). The object of this paper is to establish the main stages of the redaction (...) of the Hebrew and Latin extant versions of his astronomical work. Although Levi declares that the work was finished in 1328,1 argue that this text was the preliminary draft of the preserved one, most of which was composed after 1338. A thorough revision of the work was undertaken at an indeterminate date before 1344. It is also argued that the final form of the work was probably due to the request of solar and lunar tables made to Levi by “great and noble Christians” around 1332. (shrink)