ABSTRACT
Andalusian astronomers of the 11th and 12th century seem to have felt a certain interest in the critical study of Ptolemy’s model for Mercury. In addition, Abu Bakr b. Bajja ascribes to Ibn al-Zarqalluh an otherwise unknown short treatise on the invalidity of the method used by Ptolemy to determine the position of Mercury’s apogee. This led the author, a few years ago, to conjecture whether the anomalous position of Mercury’s apogee determined by M. Boutelle from Ibn al-Zarqalluh’s Alraaflac tables was the result of new observations made by the Toledan astronomer: it is well known that Ptolemy’s apogee for Mercury was inaccurate by about 30° in his own time, and Andalusian astronomers were probably conscious of the fact that an entirely different - and, in fact, far more correct - longitude of Mercury’s apogee appeared in al-Khwarizmi’s zfj: 224;54° for the beginning of the Hijra.
