“The Vagueries of Transmission: Case Studies on the Circulation of Islamic Astronomy”

Jamil Ragep (McGill University)

That Islamic astronomy exerted a considerable influence on pre-modern European astronomy is not in dispute. It has been difficult, however, to trace the exact trajectories by which that influence was effected in all cases; consequently, the argument that parallelism, rather than influence, is as good or better an explanation of similar models or theories has gained plausibility when evidence of direct transmission is lacking. In this paper, we will examine several cases that indicate a wide range of examples of possible influence of Islamic astronomy on European savants. These include: 1) the transmission of Naṣīr al-Dīn al-Ṭūsī’s (d. 1274) lunar model to the Byzantine scholar Gregory Chioniades (d. ca. 1320); 2) the possible influence of Ṭūsī’s device for producing rectilinear oscillation from rotating spheres on Nicole Oresme (d. 1382); 3) the anticipation by ʿAlī Qushjī (d. 1474) of the proposition in Regiomontanus’s Epitome of the Almagest showing how to transform Ptolemy’s epicycle models into eccentric ones; and 4) the virtual identity of some of Copernicus’s models with those of Ibn al-Shāṭir (d. 1375-6). In all these cases, Islamic influence has either been denied or downplayed, usually based on a parallelism argument that goes as follows: working in traditions with a common source (i.e. Greek astronomy), it is “natural” that Islamic astronomers and their European counterparts would come up with similar solutions to perceived problems. We will argue that such arguments are inadequate and that despite the “vagueries” of transmission, it offers a far more plausible explanation.

“From Marāgha to Trabzon: Transmission of Astronomical Parameters by Gregory Chioniades – An Analysis of ‘the Tables of 1093’”

Sajjad Nikfahm-Khubravan (McGill University)

At the beginning of the 14th century, Gregory Chioniades of Constantinople traveled to Azarbayjān where he came to know the Islamic astronomical corpus. Returning to Byzantium, he brought many astronomical texts. Among these texts is a series of astronomical tables for calculating planetary positions, which David Pingree called “the tables of 1093.” Three copies of these tables are extant in the Vatican and Florence libraries. These tables, whose Islamic origins has been acknowledged, but not determined, relate to a genre of Islamic astronomical writing known as “zīj.” The tables of 1093, which are calculated using the double-argument planetary equation tables and hence are easy to use, but complicate to calculate, are the subject of this paper. Up to now the nature and origins of these tables remained unknown. I present here an analysis of these tables, extract their underlying parameters, and speculate about their origins.

“A Fusion of Tables: John Chortasmenos and Persian Astronomy”

Anne-Laurence Caudano (University of Winnipeg)

By 1300, Byzantine astronomers admitted that Ptolemy’s astronomical tables were outdated and did not yield precise results. Some, therefore, sought to improve the results of their calculations by looking for other texts. Among the Persian, Latin, and Jewish works adapted in Greek in the 14th and 15th centuries, the Persian tables and methods were the most studied. Within this corpus, the Byzantines were mostly familiar with Naṣīr al-Dīn al-Ṭūsī’s Zīj-i Īlkhānī, through George Chrysokokkes’ Persian Syntaxis (ca. 1347), a version of which also circulated in Latin by the early 15th century. While some astronomers embraced these tables exclusively, others developed means to improve the Greek tables by combining them with Persian data and methods. These attempts are crystallized in the work of the patriarchal notary John Chortasmenos (fl. c. 1408-1415), whose compendia of astronomical texts and exercises include a number of eclipses calculated with the Greek and the Persian methods, as well as with an original, but awkward, system that mixed both. His manuscripts also tie him to the proto-Plethon tables (c. 1414), based on Persian parameters but later developed on an entirely new model by George Gemistos Plethon. Chortasmenos did not travel far from Constantinople, but he belonged to a tightly knit network of Byzantine astronomers / diplomats / theologians with a wider international reach that, notably, included Plethon, Bessarion and Isidore of Kiev. As such, he participated actively in the astronomical studies and exchanges that took place in the Mediterranean at the time.

“Networks and Exchange Between the Ilkhanids and the Byzantine Empire”

Robert Morrison (Bowdoin College)

The astronomy of the Ilkhanids reached the Byzantine Empire in two ways. First, the scholar Gregory Chioniades traveled to Marāgha in the late 13th century and received information on both theoretical and mathematical astronomy. The information about mathematical astronomy was the basis for a few zījes that Chioniades produced in Greek. Chioniades also learned about some of the developments in theoretical astronomy due to scholars associated with the Marāgha observatory. Scholars have understood this exchange of information about theoretical astronomy to be most significant for investigations about the background of European Renaissance astronomy. Second, another Byzantine scholar, George Chrysococcès, who traveled to Trebizond in 1347 to learn about Persian astronomy (i.e. from Marāgha), produced the Persian Syntaxis, a work later translated into Hebrew. A Jewish scholar from Constantinople, Mordechai Khumṭiano (d. 1485-90) authored a Hebrew text entitled Peirush luḥot Paras (Commentary on the Persian Tables), a defense of astronomical tables based on those produced under the Ilkhanids at Marāgha and Tabriz. There is no doubt that material from Ilkhanid zījes played a role in the scientific culture of Romaniot Jews and Byzantine Christian scholars. This presentation focuses on how Khumṭiano defended the Persian method against those of Ptolemy, who was favored by Byzantine scholars such as Isaac Argyros. It examines an Almagest commentary due to Khumṭiano and his student Elijah Mizraḥi for any trace of theoretical astronomy from Marāgha and, finally, explores the extent to which a fifteenth and sixteenth-century scholarly network in the Eastern Mediterranean facilitated this exchange.

“Immanuel Bonfil’s Book of Six Wings: The Circulation of Astronomical Knowledge over Three Centuries”

Richard Kremer (Dartmouth College)

Written around 1340 in Hebrew at Tarascon on the Rhône, the Sepher Shesh Kenaphayim (Book of Six Wings) presents six tables for predicting eclipses, largely based on the parameters and methods of al-Battani. This work, composed by the Rabbi Immanuel ben Jacob Bonfils, enjoyed considerable distribution and remains extant in 90 Hebrew manuscripts, 12 Greek manuscripts (translated in 1435), three Latin versions (translated in 1406 and 1437), and one lost Slavonic translation made in Kiev. In the 1630s, Gassendi and Peiresc had a Hebrew version that Solomon Azubi, a rabbi in Carpentras, translated into Provençal. Very few sets of medieval astronomical tables diffused through this number of languages, astronomical communities, and centuries. In this paper I will examine the contexts for the Greek, Latin and French translations of Bonfils' tables and will ask why these tables might have moved so easily given the existence, over these three centuries, of better known, competing astronomical tables.