Early Astronomy in the University of Michigan Collections

The early print of the same portion of the catalogue is taken from a 1515 edition of Ptolemy’s Almagest as translated by Gerard of Cremona (1114-1187). Gerard is the most famous translator of scientific texts from Arabic into Latin, written both by Greek authors translated into Arabic and by Islamic scholars themselves. According to his students, it was indeed the desire to read the Almagest that urged Gerard to move to Toledo in Spain, where he spent most of his life learning Arabic and then translating scientific texts written in that language into Latin. While the Almagest was his most important translation in astronomy, he also translated other astronomical texts such as Autolycus, De sphaera mota, Theodosius, Spherica, Hypsicles, De ascensionibus signorum, Thābit ibn Qurra, De motu accessionis et recessionis (also known as De motu octave spere).

Gerard translated the Arabic Almagest into Latin around 1150-1180. In particular the star catalogue by Gerard draws from two distinct version of the Almagest, the one by al-Ḥajjāj (827/8 CE) and the one by Thābit ibn Qurra (ca. 824-901 CE); which in its turn was a reworking of a previous version by Isḥāq ibn Ḥunayn (879-880 CE).

Later on, the Islamic astronomers developed their own star catalogues, the most famous of which being those by al-Battānī (880 CE), by al-Ṣūfī (964 CE), and by al-Bīrūnī (1030 CE). In these catalogues, Islamic scholars updated star coordinates on the basis of precession and added additional information or criticism of Ptolemy’s data. Yet in Europe Gerard’s translation remained the main version of the Almagest and was even used for the Alfonsine Tables (compiled under the King Alfonse X of Castille in ca. 1270), the standard astronomical tables (in the Latin version composed in Paris in ca. 1320) in Europe until Kepler published the Rudolphine Tables in 1627. In the Alfonsine tables the only change compared to Gerard’ version is the longitude of stars adapted due to precession in 1252 (namely, Ptolemy’s longitude + 17o 8΄). In fact, part of the catalogue of al-Ṣūfī was also translated into Latin and is known as Ṣūfī Latinus. However, this is a composite work and the star catalogue in particular is still the one by Gerard, this time adapted to the precession of al-Ṣūfī’s time (namely, Ptolemy’s longitude + 12o 42΄). Thus, until Copernicus the only star catalogues circulating in Europe was Gerard’s translation of Ptolemy’s Almagest, available in two versions, the catalogue appended to the Alfonsine Tables and the Ṣūfī Latinus, whose only difference was the ecliptic longitude of stars due to different value of the precession correction.

Indeed, Ptolemy’s Catalogue of Stars (in the Latin version of Gerard of Cremona) remained the standard star catalogue for more than a thousand years in the Greek-Arabic-Latin tradition, until the new star catalogues by Ulugh Bēg (Zīj-i jadīd-i sulṭānī, 1438-1439) and by Kepler (Rudolphine Tables, 1627) were published, which were both based on new and more accurate observations (in the observatory at Samarqand directed by Ulugh Bēg and, for the Rudolphine Tables, by Tycho Brahe).

Ptolemy’s Catalogue of Stars

Stars and Constellations