This is the first investigation of timekeeping by the sun and stars and the regulation of the astronomically-defined times of Muslim prayer. The study is based on over 500 medieval astronomical manuscripts first identified by the author. A second volume and third volume, also published by Brill, deals with astronomical instruments for timekeeping and other computing devices.

This paper is a technical study of the systematic observations and computations made by Muḥyī al-Dīn al-Maghribī (d. 1283) at the Maragha observatory (north-western Iran, c. 1259–1320) in order to newly determine the parameters of the Ptolemaic lunar model, as explained in his Talkhīṣ al-majisṭī, “Compendium of the Almagest.” He used three lunar eclipses on March 7, 1262, April 7, 1270, and January 24, 1274, in order to measure the lunar epicycle radius and mean motions; an observation on April 20, (...) 1264, to determine the lunar eccentricity; an observation on August 29, 1264, to test the model; and another on March 15, 1262, for measuring the lunar parallax. In the second period of activity at the Maragha observatory, Shams al-Dīn Muḥammad al-Wābkanawī (c. 1254–1320) adopted all of al-Maghribī’s parameter values in his Zīj, but decreased his value for the mean longitude of the moon at epoch by 0;13,11∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{\circ }$$\end{document}. By comparing the times of the new moons and lunar eclipses in the period of 1270–1320 as computed from the astronomical tables of the Maragha tradition with the true modern ones, it is argued that this correction was very probably the result of actual observations. (shrink)

ArgumentThe present paper is an attempt to understand how medieval astronomers working within the Ptolemaic astronomical context in which the annular eclipse is an unjustified and impossible phenomenon, could know, define, justify, and later make attempts that led to success in predicting annular solar eclipses. As a context-based study, it reviews the situation of annular eclipses with regard to the medieval hypotheses applied to the calculation of the angular diameters of the sun and the moon, which was basic for contemplating (...) the possibility of annular eclipses. This gives the premises and the preliminary insights that were necessary to clarify the complex situation of the annular eclipse in the late medieval Islamic period and to explain the historical mechanisms leading to justifying the phenomenon during that period. This was, first due to a convincing and efficient observational evidence which, of course, was available only to a number of medieval astronomers and significantly for only a limited time period, and, second, the result of an amazing interaction amongst various astronomical traditions available to them. At a more general level, the research aims to inspect or, at least, to give some impressions of the essential conditions, i.e., identification of phenomenon, empirical evidence, and the justifying underlying tradition, under which it became possible in the tradition-based science of the `medieval period to permit a not-already-defined and tradition-opposed phenomenon to be posed and justified. (shrink)

Avner Ben-Zaken reconsiders the fundamental question of how early modern scientific thought traveled between Western and Eastern cultures in the age of the so-called Scientific Revolution. -/- Through five meticulously researched case studies—in which he explores how a single obscure object or text moved in the Eastern world—Ben-Zaken reveals the intricate ways that scientific knowledge moved across cultures. His diligent exploration traces the eastward flow of post-Copernican cosmologies and scientific discoveries, showing how these ideas were disseminated, modified, and applied to (...) local cultures. -/- Never before has a student of scientific traffic in the Mediterranean taken such pains to see precisely which instruments, books, and ideas first appeared where, in whose hands, by what means, and with what implications. In doing so, Ben-Zaken challenges accepted views of Western primacy in this fruitful exchange. He shows not only how Islamic cultures benefited from European scientific knowledge but also how Eastern understanding of classical Greek texts informed developments in the West. -/- Ben-Zaken’s mastery of different cultures and languages uniquely positions him to tell this intriguing story. His findings reshape our understanding of scientific discourse in this critical period and contribute to the growing field of cross-cultural Christian-Muslim studies. (shrink)