ABSTRACT
An Andalusian tradition of zijes seems to have been predominant in the Maghrib due to the popularity of the ztj of Ibn Ishaq al-Tunisi and derived texts compiled in the fourteenth century. This tradition also used Ibn al-Zarqalluh’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 Zarqallian trepidation theory, while the obliquity of the ecliptic had diminished below the level accepted by astronomers who followed Ibn al-Zarqalluh.
