Ibn 'Azzuz al-Qusantini's tables for computing planetary aspects

Abstract

This paper presents a chapter of the fourteenth century al-Zīj al-Muwāfiq by Ibn al-Azzūz al-Qusantīnī (d 1354) containing the only known example of numerical tables designed for the computation of the astrological aspects following the most popular method for this practice in the Islamic area: that of lhe Single Hour Line. Ibn Azzūz presents two different procedures. The first one illustrates, according to the author. the method normally used in his time, mentioned by 'Ptolemy and Hermes', and transmitted by Abu Ma'shar. The second one is lhe technique that he uses for computing his tables for the latitude of Fes. The geometrical approach of both procedures is the same and what lbn Azzūz offers with his tables is a computational tool that aims to improve (he system avoiding certain errors produced by previous algorilhms. Nevertheless, Ibn Azzūz's final belief is that the computation for lhe aspects must be performed on the ecliptic following the simple method - consisting of adding or subtracting the different aspects to the ecliptical longitude of the star or planet -. whereas the use of his tables is more appropriate for another astrological practice: the tasyīr or system of progressions.