In this selection of studies, J.L. Mancha explores aspects of the development of medieval optics and astronomy, including some medieval antecedents of the work of early modern astronomers. The articles deal with Latin, Hebrew and Arabic texts, and the process of translation and transmission of knowledge, and focus on three main themes. First, the theory and astronomical use of the pinhole camera in the 12th and 13th centuries; the texts edited here contain a solution to the problem of the formation of images cast by light through triangular apertures, equivalent to Kepler's, a description of the correct procedure for measuring solar apparent diameters using finite apertures, and a derivation of the Sun's eccentricity from its apparent diameters at apogee and perigee. Second, the characteristics of the Latin and Provençal versions of Levi ben Gerson's astronomical work, composed in collaboration with the author, as well as his tables and canons for finding syzygies and the mathematical methods used in the derivation of parameters. Third, different aspects of the survival of homocentric astronomy in the Middle Ages, especially al-Bitruji's model for trepidation and the technique for calculating the hippopede resulting from Eudoxan couples.

In this selection of studies, J.L. Mancha explores aspects of the development of medieval optics and astronomy, including some medieval antecedents of the work of early modern astronomers. The articles deal with Latin, Hebrew and Arabic texts, and the process of translation and transmission of knowledge, and focus on three main themes: the theory and astronomical use of the pinhole camera in the 12th and 13th centuries; the characteristics of the Latin and Provençal versions of Levi ben Gerson's astronomical work; and different aspects of the survival of homocentric astronomy in the Middle Ages, especially al-Bitruji's model for trepidation and the technique for calculating the hippopede resulting from Eudoxan couples.

In Measuring Shadows, Raz Chen-Morris demonstrates that a close study of Kepler’s Optics is essential to understanding his astronomical work and his scientific epistemology. He explores Kepler’s radical break from scientific and epistemological traditions and shows how the seventeenth-century astronomer posited new ways to view scientific truth and knowledge. Chen-Morris reveals how Kepler’s ideas about the formation of images on the retina and the geometrics of the camera obscura, as well as his astronomical observations, advanced the argument that physical reality could only be described through artificially produced shadows, reflections, and refractions. Breaking from medieval and Renaissance traditions that insisted upon direct sensory perception, Kepler advocated for instruments as mediators between the eye and physical reality, and for mathematical language to describe motion. It was only through this kind of knowledge, he argued, that observation could produce certainty about the heavens. Not only was this conception of visibility crucial to advancing the early modern understanding of vision and the retina, but it affected how people during that period approached and understood the world around them.

Today few would think of astronomy and astrology as fields related to theology. Fewer still would know that physically absorbing planetary rays was once considered to have medical and psychological effects. But this was the understanding of light radiation held by certain natural philosophers of early modern Europe, and that, argues Mary Quinlan-McGrath, was why educated people of the Renaissance commissioned artworks centered on astrological themes and practices. Influences is the first book to reveal how important Renaissance artworks were designed to be not only beautiful but also—perhaps even primarily—functional. From the fresco cycles at Caprarola, to the Vatican’s Sala dei Pontefici, to the Villa Farnesina, these great works were commissioned to selectively capture and then transmit celestial radiation, influencing the bodies and minds of their audiences. Quinlan-McGrath examines the sophisticated logic behind these theories and practices and, along the way, sheds light on early creation theory; the relationship between astrology and natural theology; and the protochemistry, physics, and mathematics of rays. An original and intellectually stimulating study, Influences adds a new dimension to the understanding of aesthetics among Renaissance patrons and a new meaning to the seductive powers of art.

This is the fourth set of studies in the Variorum series by David King, a leading authority on the history of astronomy in Islamic civilization and on medieval astronomical instruments, European as well as Islamic. The first of the eleven studies collected here deals with medieval instruments in general, as precious historical sources. The following papers focus on individual astrolabes from the European Middle Ages and early Renaissance that are of singular historical importance. Two look at the origins of the simple universal horary quadrant and the complicated universal horary dial (navicula). The collection concludes with a list of all known medieval European astrolabes, ordered chronologically by region. Three "landmark" astrolabes are discussed: (1) the earliest known European astrolabe from 10th-century Catalonia, that milieu in which the astrolabe first became known to Europeans; (2) an astrolabe from 14th-century Picardy bearing numerals written in monastic ciphers as well as a later dedication mentioning two friends of Erasmus; (3) the splendid astrolabe presented in 1462 by the German astronomer Regiomontanus to his patron Cardinal Bessarion, with its enigmatic angel and Latin dedication, here presented in the context of other astrolabes of similar design from 15th-century Vienna.

This is a survey of the numerous astronomical tables compiled in the late Middle Ages, which represent a major intellectual enterprise. Such tables were often the best way available at the time for transmitting precise information to the reader.

Gersonides was a highly original Jewish philosopher, scientist and biblical exegete, active in Provence in the first half of the fourteenth century. Ruth Glasner explores his impressive achievements, and argues that the key to understanding his originality is his perspective as an applied mathematical scientist. It was this perspective that led him to examine Aristotelianism from directions different from those usually adopted by contemporary scholastic scholars. Gersonides started on his way, as he himself claims, as a 'mathematician, natural scientist, and philosopher', who believed in his power to solve the main problems of medieval science. He ended up concentrating on his work as a mathematical astronomer, developing techniques of observation and computation, and somewhat less optimistic about the prospect of scientific knowledge.