Early Astronomy in the University of Michigan Collections

The Babylonians used a luni-solar calendar with months defined by the cycle of lunar visibility. Because twelve months fall short of the solar year by about eleven days, the Babylonians intercalated an extra month roughly once every three years in order to keep the calendar in line with the seasons. Various rules are preserved in astronomical texts for deciding when to intercalate. These rules fall into two main groups: in one group, an intercalation is performed if the first visibility of a star/constellation occurs one month later than its expected date; in the other, intercalations are triggered by observing whether or not the moon and the constellation “The Stars” (= the Pleiades) are in conjunction on specified dates during the year. In this talk, I will present these various rules and discuss their relationship to one another and whether or not they were used in practice.

Most of the so-called Normal Stars, which Babylonian astronomers used for tracing the motion of the Moon and the planets, are securely identified. What do they tell us about the Babylonian zodiacal constellations to which they belong? In this presentation I discuss some groups of Normal Stars in relation to other Babylonian sources about the zodiacal constellations.

In Almagest VII Ptolemy addresses, among other topics, the question of precession: its discovery by Hipparchus, and the extent to which this motion affects the positions of the stars. As part of that effort, Ptolemy discusses in chapter I some stellar configurations described in an earlier Hipparchian work, and other configurations provided by Ptolemy himself. My paper is centered on those stellar configurations. I will focus on the precision of Ptolemy’s descriptions, and compare his own alignments with Hipparchus’. Finally, I will discuss some textual hypotheses that can be drawn from the study of the chapter.

The relationship between Hipparchus’ star catalogue and Ptolemy’s star catalogue in the Almagest has been object of discussion since the time of Tycho Brahe. In this work, I will focus on how these two ancient astronomers conceived and described constellations. The differences between Hipparchus’ and Ptolemy’s descriptions of constellations show that Ptolemy did change Hipparchus’ catalogue: I will highlight some of the reasons why Ptolemy made changes to Hipparchus’ catalogue and descriptions and discuss how star lore developed from the Hellenistic period to the second century CE.

Numerous Greek horoscopes are preserved from antiquity on various media, but above all on papyri; additionally, many horoscopes have been transmitted through the medieval manuscript tradition. The basic minimum data constituting a horoscopic document—a birthdate, the zodiacal locations of the Sun, Moon, and planets on that date, and the ascendant zodiacal sign or point—could be augmented in various ways. This talk looks at one of the less common “add-ons” found in a few elaborate horoscopes on papyrus or in the manuscript tradition, citations of fixed stars in the zodiacal belt near which each of the heavenly bodies was located at the nativity. Two recently discovered papyrus horoscopes dating to the third and fourth century CE, as well as the more well-known “horoscope of Eutocius” transmitted in Byzantine astrological codices, relied on Ptolemy’s star names and coordinates for these data, and I will argue that such horoscopic applications were one of the primary motivations for the zodiacal star list in Ptolemy’s Handy Tables. However, the practice of including fixed stars in Greek horoscopes can be traced well before Ptolemy.

In this work in progress paper, I focus on the descriptions and depictions of the Bull, Argo and Horse in Hellenistic texts and material culture. These constellations were represented in a variety of ways, which included half figures. By examining a range of sources, such as poetry, celestial objects and artworks, I aim to identify common and divergent patterns, and sources of inspiration across different depictions of these constellations as cut-off figures. An initial analysis reveals that during the Hellenistic period at least two iconographical traditions for these constellations emerged, which have endured to the present day.

After presenting the extant evidence from Hipparchus’ Star Catalogue, I will discuss their significance for the history of astronomy, and prospects for further textual discoveries.

The ‘Heavenly Offices’ treatise’s first section, found in the Records of the Grand Historian, is the oldest transmitted Chinese star catalogue. In this catalogue, Sima Qian names asterisms whose positions are either assumed to be known or given relative to other asterisms. This talk will describe how Sima Qian systematically charts his way through the night sky and discuss in particular how he expresses the relative positions of asterisms.

We are well acquainted with some evidence of constellations from Ancient Egypt, especially concerning the decans and the Ramesside star clocks. However, only a limited inventory of constellations is depicted there. In particular, in the system of the “classical sky image” one finds representations of several constellations of the northern sky on the one hand, and a few areas of the decans on the other. The other decans and likewise all the constellations of the Ramesside star clocks do not receive any visualization. This lecture will try to reconstruct the Egyptian conception of the constellations primarily on the basis of the names and to appreciate it in comparison with that of other regions (especially Mesopotamia). Finally, it will also be examined to what extent the constellations on the round celestial image of Dendara continue native traditions or whether foreign influences can be grasped.

Egyptian astronomical and astrological texts attest the use of the zodiacal signs as a framework for the division of the ecliptic into 12 equal parts since the Ptolemaic period. The names of these signs are written in a variety of forms, from complete orthographies in the demotic script, to a mix of hieratic and demotic. Demotic astronomical tables and horoscopes, due to their generally concise character, tend to employ abbreviated writings of the zodiacal signs, mostly limited to one sign, sometimes followed by a star determinative. These abbreviated forms received scholarly attention early on, being proposed as the origin of the modern symbols for the zodiacal signs. While this has been proven for some of them, the connection is not clear for all. In this lecture, I will present a state of the question on our evidence for demotic abbreviated forms of the zodiacal signs, incorporating some new attestations from recently published and unpublished sources, and discussing their formation, variations, and rationale within the corpus. I will also briefly set them in parallel to the symbols used in a series of later Greek and Syriac astronomical and alchemical manuscripts, discussing the issues that each transmission context entail.

‘Abd al-Rahman al-Sufi claims in his leg preface to his most famous work that he visualized the heavens in order to teach people to learn how to accurately see the stars. For this purpose he divided his presentation of the 48 constellation of Almagest into description, tabulation and visualization. It is all the more surprising that a study of these 48 units contradicts the goals of the price. I plan to discuss those contradictions for an example of each of the three parts of his book: the northern constellation, the Zodiac and the southern constellation.

In this presentation I am going to introduce images of Ursa Maior/Big Dipper from different cultural contexts on different objects with different cultural usage. I will discuss the appearance and meaning of the constellation and its various parts and ask whether these differences are determined by the specific contexts in which the images were produced and used. I will compare images from Europe and the Middle East with East Asian depictions in order to elucidate cultural differences in how the constellation was perceived.

In 1524, Peter Apian published two closely related works—one the Latin Cosmographicus liber, aimed at an educated audience of international readers, and the other, Ein kunstlich Instrument, a shorter, more practical book for those who could read German but had no Latin. While the two works differ greatly in content, both nevertheless make use of the many of the same instruments, including Apian’s early volvelles. While the Cosmographicus liber has received much scholarly attention, Ein kunstlich Instrument has received very little. We shall compare and contrast the two works to elucidate Apian’s conception of the needs and desires of his audiences.

Tycho’s star catalog enjoyed enormous prestige for centuries due to its accuracy. The entire catalog depends on the coordinates of one single star, Hamal (α Arietis), which explains why Tycho was so scrupulous in determining its coordinates using two different methods applied to more than 50 observations, as he described in his Progymnasmata. One of them proposed an ingenious way of dealing with refraction and parallax, two factors that he knew he could not control. Selecting particular observations, he was able to cancel out the effects of both refraction and parallax. Still, the entire calculation starts from the coordinates of the Sun calculated from his solar model. But Tycho’s solar model assumes too large of an eccentricity, producing errors in the predictions of the solar longitude that can reach up to 8’. In this talk, I describe Tycho’s method for calculating the coordinates of α Arietis and explain how the method he proposed unintentionally avoided transferring the error of his solar model to his catalog.