Isaac Israeli ben Joseph

He was a pupil of Asher ben Yehiel, at whose request (in 1310) he wrote the astronomical work Yesod Olam.

The book includes chapters on: geometry and trigonometry; the structure and position of the globe; the number and movements of celestial spheres; the time differences in days and nights in various parts of the Earth; the movements of sun and moon; solstices, neomeniæ, eclipses, and leap-years.

It also deals with the chronological systems of other nations and religions (iv, § 17), especially Christianity, and lists notable personages of the Biblical, Talmudic, and geonic periods, as per Sefer ha-Qabbalah of Abraham ibn Daud, in chronological order (iv, § 18).

Isaac al-Hadib, Judah Bassan, and Elijah Mizrahi annotated it, and an anonymous author wrote a commentary on it (Neubauer, Cat.

An abridgment was made in Arabic by the author's son Joseph Israeli ben Isaac, of which the Hebrew translation, Kitzur Yesod Olam is still extant (ib.