Pre-modern astronomers often analyzed the longitudinal motion of the planets through the ecliptic, the path traced by the sun around the earth, in isolation from the motion of the planets in latitude to the north and south of the ecliptic. Although the models, i.e. configurations of orbs, for latitudes could be integrated into those for longitudes, astronomers presented them separately. Historians of astronomy in Islamic societies and in Jewish cultures, whether they study theoretical models or tables, have researched planetary longitudes much more than planetary latitudes. This imbalance may be because planetary latitudes did not have applications whereas longitudes had many.

In this presentation, I survey of the theories of Levi ben Gerson (1288-1344), a.k.a. Gersonides, for the motions of the planets in latitude. Levi was one of the most significant pre-modern Jewish scholars and has been judged to be the most creative pre-modern Jewish astronomer. Although Levi drew on the latitude theory of the Almagest, he also incorporated elements of the latitude models found in the Planetary Hypotheses into his own models.

Levi’s models for the planets’ motion in latitude are distinctive in that he transferred some of the building blocks of Ptolemy’s models from the Planetary Hypotheses to models from which epicycles were excluded. Levi’s latitude models are also distinctive because he theorized that one of the concentric orbs in the latitude models for Jupiter and Saturn revolved at twice the angular velocity of the other.

Athīr Dīn Abharī (d. 1265) was especially known as the author of philosophical works such as Īsāghūjī (Introduction to Aristotelian Logic) and Hidāyat al- Ḥikma (Summary of Aristotelian Philosophy). His scholarship was not limited to philosophy. He also wrote several books on mathematics and astronomy, including the largest extant astronomical work, Utmost Attainment in Comprehending the Orbs (Ghāyat al-idrāk fī dirāyat al-aflāk).

We notice that the Utmost Attainment has a section on the configuration of the cosmos (= ‘ilm al-hay’a), and besides the Utmost Attainment, he composed several works containing a section on the ‘ilm al-hay’a. Remarkably, it is known that Abharī learned astronomy under the supervision of Kamāl al-Dīn ibn Yūnus, a teacher of Naṣīr al-Dīn al-Ṭūsī on astronomy. This episode confirms that Abharī and Ṭūsī shared the same tradition of astronomical education, probably including topics concerning the ‘ilm al-hay’a

In this paper, I will elucidate Abharī’s version of the ‘ilm al-hay’a, which in turn I will reveal the standard frame of the ‘ilm al-hay’a around the time of Ṭūsī and the innovative aspect of the ‘ilm al-hay’a in the post-Avicennian period.