Astrolabes in Medieval Jewish Culture

What was the role of the astrolabe in Jewish culture? It was as important as the role it played in Muslim and Christian cultures: the astrolabe was the most symbolic of medieval astronomical instruments and embodied the best astronomical knowledge then available. It was associated with power and luxury in the Muslim and Christian courts, where astrologers (frequently Jews) used it to forecast the future of the king and his kingdom.

Astrolabes were occasionally treated like jewels, and as such, they were embellished with precious stones and displayed in public. They were (and still are) collectible items that indicated on the metal of the mater the names of the patron and the maker.  Very few astrolabes with Hebrew script are extant; they are characteristically restrained in their decoration, which makes the Hebrew script especially noticeable.

There is sufficient (instrumental and textual) evidence that Jews were involved in the diffusion of the astrolabe through texts and instruments. Some of them, like Levi ben Gerson (13th c.), introduced improvements and modifications in the standard planispheric astrolabe. Others, like Abraham ibn Ezra, found in the biblical text indications of its knowledge among the Israelites before its invention by Greeks.

Research about the astrolabe in Jewish culture and the degree of involvement of Jews in astrolabe making and astrolabe diffusion is still lacking in the fields of Jewish studies and of the history of science. Researchers should pay attention to the fact that astrolabes in Jewish culture employed many languages (Hebrew, Catalan, Judaeo-Arabic, Arabic, and Castilian) and were used in very different contexts, which was a reflection of the complexity and diversity of Jewish culture in the Middle Ages.

The Hebrew astrolabes displayed at the British Museum in London and at the Adler Planetarium in Chicago are interdisciplinary artefacts made in the interplay of medieval science (astronomy), medieval practice (astrology), and medieval philosophy (cosmology). They took their form and were preserved and modified in the context of an ensemble of knowledge whose texts and instruments travelled much more than usually assumed and whose writers, readers, and makers were less homogeneous than previously believed. All of this indisputably makes the astrolabe a fascinating artefact and an illuminating object about Jewish culture in the Middle Ages.

Find out more on the research project blog

This illumination comes from a manuscript belonging to the Jewish Community of Copenhagen and deposited in the Royal Library of this city. The manuscript is the Hebrew translation of Maimonides' Guide for the Perplexed. Maimonides (born in Cordova 1135 or 1138) is possibly the most prestigious Jewish scholar of the Middle Ages in several fields, religious law, philosophy, and science. His Guide for the Perplexed, written in Judaeo-Arabic (Arabic in Hebrew script), is a paramount work in Jewish philosophy. Levi ben Isaac Ben Caro of Salamanca copied this manuscript of Maimonides' Guide for the physician of Pedro IV el Ceremonioso, Menachem Betsalel, in Barcelone in 1347-48. The illuminations in the manuscript were made by several hands, but Ferrer Bassa, a Christian from Barcelona, seems to be the main illuminator. It seems that both, copyist and illuminator, became victims of the Black Death that broke out in Europe in 1348.

What we see on this illumination is Ptolemy, or maybe Aristotle, as a Jew (maybe Maimonides himself), who sits on a throne with stars of David and holds an astrolabe in his right hand, in front of a group of Jews. 

The scene is surmounted by a blue sphere covered with golden stars, among which the sun and the moon, in contrast to reality, are shining at the same time. The stars depicted on the throne and the stars depicted in the sky attest eloquently to the natural relationship of Jews with the sciences of the stars (astronomy and astrology) from ancient times. The astrolabe that the Jewish astronomer holds in his hand shows us its back side with its characteristic sighting device, the alidade. One used it in calculation, by making it point to the different divisions on the surface of the astrolabe, and also in surveying, by making it point to any star in the sky by means of the sighting vanes placed at both extremes of it.

The Jewish astronomer holds the astrolabe by its upper part, where the throne should have been. Yet this instrument does not seem to have that characteristic protruding part to which a chain was attached, but rather the astrolabe seems to be equipped with a handle that the astronomer holds. Blue stars are scattered all around the astronomer between the sphere of the sky and the ground. This feature of the illumination is a witness of the horror vacui that permeated medieval cosmology and medieval art and, above all, an indication of the relationship (analogy) between the heavenly bodies and the terrestrial beings in medieval thought and cosmology.

Josefina Rodriguez-Arribas, Researcher

Abraham ibn Ezra, On the Astrolabe, Russian Academy of Sciences, St Petersburg, MS B300

I found astrolabes soon in my life as a researcher of medieval Jewish culture and language. Abraham ibn Ezra, who introduced contemporary science so skilfully into his biblical commentaries, refers to the astrolabe a couple of times in these commentaries. So I found the expression kli ha-nehoshet (i.e., 'the copper / brass instrument') for the first time in Ibn Ezra, when I was preparing my PhD dissertation on Ibn Ezra's texts. This was not unexpected, for he was the first to introduce this biblical expression to denote astrolabes. Later, researching on the emergence of technical terminology in medieval Hebrew, I frequently found this word and others denoting the astrolabe in medieval Hebrew texts. I can say that this fascinating instrument and its relationship to Jewish culture has been making its way to my attention through many texts and many words and, eventually, has become the subject of a  research group to which I belong. My focus is not only the astrolabe depicted and explained in medieval manuscripts, but also the extant astrolabes bearing inscriptions in Hebrew or Judaeo-Arabic (Hebrew script is certainly a sure sign of Jewish identity, among many others). People frequently associate astrolabes with navigation. Although the instrument used in navigation was a simplified version of the more complex planispheric astrolabe and its use did not start until the 15th century, I would like to keep this image of seas and new lands associated to our research; for the astrolabe is bringing us  a new insight into many aspects of the life and interests of medieval Jews, and some discoveries.

Charles Burnett, Investigator

Al-Sufi, Book of Fixed Stars, Iran 1675, The David Collection (Copenhagen)

In the Middle Ages knowledge of the astrolabe was always regarded as being essential to any study of the science of the stars. Thus, the Tractatus astrolabii attributed to Masha’allah was part of the curriculum on astronomy at medieval universities and has survived in over a hundred and fifty copies. My own research has looked at the period when the astrolabe, and texts relating to it, were first brought into Europe from the Arabic world—a period which preceded and led to the formation of the first universities. Latin texts on the astrolabe first appear in Catalonia in the tenth century at the same time and in the same place as the earliest extant European astrolabe. Adelard of Bath (ca. 1080 – ca. 1152), whose mathematical texts I am in the process of editing, composed a work on the use of the astrolabe, as well as translating from Arabic astronomical tables, an introduction to astrology, astrological aphorisms and a work on the construction of astronomical talismans. I have collaborated with Emanuelle Poule in editing the works of Raymond of Marseilles (fl. 1141), one of the earliest Latin writers of the twelfth century to show how the Arabic-Latin texts were received; he wrote on the astrolabe, and on astronomical tables as well as on astrological ‘judgements’. I am interested to see how the presence of the astrolabe in medieval Jewish society parallels that of Arabic and medieval Christian society. Hebrew scholars worked in close collaboration with Christian scholars in the Iberian peninsula and the South of France, and both were translating into their respective languages the same Arabic texts. It is instructive to discovery both what was shared between Muslims, Jews and Christians, and the distinctive elements in their cultures.

Stephen Johnston, Co-Investigator

Medieval astrolabe with mark of Jewish owner (Tzvi Herz), Science Museum London

The Museum of the History of Science in Oxford has the world’s largest collection of astrolabes. I have worked there since 1995 and been involved in a number of projects which have presented these instruments in exhibitions, online resources and directly to the public in talks and lectures. All our astrolabes were re-examined for “The Astrolabe, East and West” (2005), a project which juxtaposed Islamic and European instruments, drawing out common themes in their construction and use. However, the collection has no astrolabes inscribed in Hebrew and the role of the instrument in Jewish culture has not been a focus of the museum’s attention. The attraction of examining “Astrolabes in Medieval Jewish Society” is in seeing a familiar device in a novel cultural context, important both in its own right and in deepening our understanding of the astrolabe’s role in medieval culture more generally. There is also the possibility that locating and documenting surviving Hebrew instruments might lead to a future acquisition for the museum. By demonstrating the importance of the astrolabe in Jewish culture, the project makes it all the more desirable to fill this notable gap in the museum’s collection.