Navigation - Astrolabe Astrolabe The astrolabe is a very ancient astronomical computer for solving problems relating to time and the position of the Sun and stars in the sky. Evidence suggests that the history of the astrolabe begins more than two thousand years ago. The principles behind the astrolabe projection were almost certainly known before 150 B.C., but the first known astrolabe is believed to have been developed in Alexandria about 160 B.C. by a Greek man named Hipparchus. A marriage of the planisphere and dioptra, the astrolabe was effectively an analog calculator capable of working out several different kinds of problems in spherical astronomy. Theon of Alexandria wrote a detailed treatise on the astrolabe, and Lewis (2001) argues that Ptolemy used an astrolabe to make the astronomical observations recorded in the Tetrabiblos. Since that first model history has recorded many variations of astrolabes, including a traditional design for use on land, the Mariner's Astrolabe and the Universal Astrolabe, just to name a few.

By far the most popular type is the planispheric astrolabe, on which the celestial sphere is projected onto the plane of the equator. There is often some confusion between the traditional astrolabe and the mariner's astrolabe. While the traditional astrolabe could be useful for determining latitude on land, it is an awkward instrument for use on the heaving deck of a ship or in wind. The mariner's astrolabe was developed to address these issues by simplifying the devices functionality and compacting it's design. Astrolabes are used to show how the sky looks at a specific place at a given time. This is done by drawing the sky on the face of the astrolabe and marking it so positions in the sky are easy to find. To use an astrolabe, you adjust the moveable components to a specific date and time. Once set, the entire sky, both visible and invisible, is represented on the face of the instrument. This allows a great many astronomical problems to be solved in a very visual way. The astrolabe quickly became the dominant historical astronomical instrument used by classical astronomers, navigators, and astrologers.

Its many uses included locating and predicting the positions of the Sun, Moon, planets and stars; determining local time given local latitude and vice-versa; surveying; and triangulation. Brass astrolabes were developed in the medieval Islamic world, chiefly as an aid to navigation and as a way of finding the qibla, the direction of Mecca. The first person credited with building the astrolabe in the Islamic world is reportedly the 8th century Persian mathematician al-Fazari. The mathematical background was established by the Arab astronomer al-Battani in his treatise Kitab az-Zij (ca. 920 AD), which was translated into Latin by Plato Tiburtinus (De Motu Stellarum). The earliest surviving astrolabe is dated AH 315 (927/8 AD). In the Islamic world, astrolabes were used to find the times of sunrise and the rising of fixed stars, to help schedule morning prayers (salat).

In the 10th century, al-Sufi first described over 1,000 different uses of an astrolabe, in areas as diverse as astronomy, astrology, horoscopes, navigation, surveying, timekeeping, prayer, Salah, Qibla, etc. Arzachel (al-Zarqali) of al-Andalus constructed the first universal astrolabe instrument which, unlike its predecessors, did not depend on the latitude of the observer, and could be used from anywhere on the Earth. This instrument became known in Europe as the "Saphaea". The astrolabe was introduced to other parts of Europe via Al-Andalus in the 11th century. Early Christian recipients of Arab astronomy included Gerbert of Aurillac and Hermannus Contractus. The first geared mechanical astrolabe was later developed by Abi Bakr of Isfahan in 1235. As testament to the astrolabe's capabilities, mathematicians throughout the ages continued to publish work after work on new applications for the device. The English author Geoffrey Chaucer (ca.

1343�1400) compiled a treatise on the astrolabe for his son, mainly based on Messahalla. The same source was translated by the French astronomer and astrologer Pelerin de Prusse and others. The first printed book on the subject of the astrolabe was Composition and Use of Astrolabe by Cristannus de Prachaticz, also using Messahalla, but relatively original. In 1370, the first Indian treatise on the astrolabe was written by the Jain astronomer Mahendra Suri and in the 16th century, Johannes St�ffler published Elucidatio fabricae ususque astrolabii, a manual of the construction and use of the astrolabe. The first known European metal astrolabe was developed in the 15th century by Rabbi Abraham Zacuto in Lisbon. In the 15th century, the French instrument-maker Jean Fusoris (ca.

1365�1436) also started selling astrolabes in his shop in Paris, along with portable sundials and other popular scientific gadgets of the day Four identical 16th century astrolabes made by Georg Hartmann provide some of the earliest evidence for batch production by division of labor. Astrolabes are still appreciated today for their unique capabilities, their elegant beauty, and their value for astronomy education. Additional Information: Astrolabe for sale. The astrolabe shop proposes the biggest choice of astrolabes in America. Details | View Technical Globes 1. An astrolabe is a very ancient astronomical computer for solving problems relating to time (what time is it ?) and the position of the Sun and stars in the sky. 2. Astrolabes are used to show how the sky looks at a specific place (latitude) at a given time. This is done by drawing the sky on the face of the astrolabe. To use an astrolabe, you adjust the moveable components to a specific date and time. Once set, much of the sky, both visible and invisible, is represented on the face of the instrument.

Typical uses of the astrolabe include finding the time during the day or night, finding the time of a celestial event such as sunrise or sunset and as a handy reference of celestial positions. 3. The history of the astrolabe begins more than two thousand years ago. The principles of the astrolabe projection (stereographic projection) were known before 150 B.C., and true astrolabes were made before A.D. 400. The astrolabe was highly developed in the Islamic world by 800 and was introduced to Europe from Islamic Spain (al-Andalus) in the early 12th century. It was the most popular astronomical instrument until about 1650, when it was replaced by more specialized and accurate instruments. 4. All our astrolabes are fully functionnal. Each astrolabe is calculated and built for a specific latitude; you will find the accuray of each astrolabe in the product description 5. All our astrolabes are shipped complete with a hardwood display stand and a user guide with ad hoc exercises. 6. All our astrolabes are high quality products that we guarantee directly. They are made in Europe.

Astrolabes in Medieval Jewish Culture -Astrolabes in Medieval Jewish Culture Astrolabes in Medieval Jewish Culture 24-25 APRIL 2014 ORGANISED BY: Josefina Rodriguez-Arribas and Charles Burnett (Warburg Institute) and Stephen Johnston (Oxford Museum for the History of Science) The TOPICS covered by this conference will be the astrolabe itself, texts on the construction and use of the instrument, and the position of the astrolabe in pre-modern cultures and societies (Islam and India, Jewish societies and medieval and Renaissance Europe). SPEAKERS will include: Charles Burnett (Warburg Institute), Laura Fernandez Fernandez (Complutense Madrid), Stephen Johnston (Museum of the History of Science, Oxford), Sreeramula Rajeswara Sarma (Stuttgart), Emilia Calvo Labarta (Universidad de Barcelona), Josefina Rodríguez Arribas (Warburg Institute), Petra Schmidl (Bonn), Johannes Thomann (Zürich), Flora Vafea (Cairo), Koenraad van Cleepoel (CNHS, Bruxelles), and Miquel Forcada (Universidad ode Barcelona).

REGISTRATION – Attendance is free of charge, but pre-registration is required by emailing ( warburg(at)sas.ac.uk) giving your name, email address, and the name of your institution (if relevant). The conference will last 1.5 days, from approx 2 pm on 24 April and then the whole day on 25 April (from approx 10.15 to 17.00). The conference PROGRAMME will be posted in due course ( ). We hope to see you there!! Reply TODAY JOHANNES THOMANN (by Prof. Charles Burnett) Johannes Thomann is a Research Fellow and Librarian at the Institute of Asian and Oriental Studies at the University of Zurich ( ). He has written extensively on medieval physiognomy in the Sanskrit, Arabic and Western traditions, on the history of astronomy, and on the depiction of astronomical events in art. ChB: Could you tell us the main trends and aims in your research in Islamic astronomy? JTh: In the near future I intend to publish an edition of Arabic astronomical documents preserved in papyrological collections in Vienna, Strasbourg, Berlin and Florence.

These are mainly horoscopes, ephemerides, almanacs and some fragments from codices. They date from the 9th to the 13th centuries and are first hand witnesses of astronomical practice in this epoch. In a second project I am editing an Arabic commentary on books IX to XIII of Ptolemy’s Almagest which has been attributed to al-Farabi. In parallel to this text I will edit also Ishaq Ibn Hunayn’s translation of the Almagest (books IX to XIII), which was the textual basis of that commentary. Further I am editing the two versions of astronomical tables by Habash al-Hasib. ChB: From your experience, how was the astrolabe used in the Islamic Middle Ages? JTh: In Baghdad, the centre of the Islamic realm from the mid-eighth century onwards, the astrolabe played a crucial role in teaching at the beginning of the 9th century and later. The size of early astrolabes was very small and they were not suitable for productive tasks in astronomy since they were not sufficiently precise. The great number of treatises and their content with basic exercises makes it likely that they represent the standard procedure of introductory teaching in astronomy.

ChB: How was teaching with the astrolabe integrated with the use of other texts in a curriculum in astronomy? JTh: It seems that there was a three step development in teaching astronomy in Baghdad. The oldest Arabic texts of the 8th century were in verse and used for memorising. This was the Indian method of learning since all known Sanskrit work of the sixth to the eighth centuries were in verse too. These contain also chapters on the use of astronomical instruments. However, the plane astrolabe became known in Baghdad from Greek and Syriac sources, and became the main teaching tool in astronomy. Texts on the use of the astrolabe are written in an instructional style, often in imperative form. They give the impression of astronomy lessons of a master to his pupil. It took some time before the Almagest became a textbook in teaching. The context was different from the earlier works. The commentary of al-Farabi (or of one of al-Farabi’s colleagues) shows that astronomy was taught within a philosophical curriculum which culminated in the topic of metaphysics. In this context, technical aspects of astronomy were not important, but emphasis was given to the description of geometrical models.

ChB: If astrolabes were solely used as teaching instruments, why do we have such well-made and expensively produced specimens from the Islamic world? JTh: The one example from from early Abbasid time (9th century) is significantly different in size and perfection from the beautiful instruments made in later times. It was suitable as an tool for exercise and demonstration, but hardly useful for serious astronomical tasks. ChB: How long did the astrolabe continue to be used in the Islamic world? JTh: Two horoscopes on a piece of paper in the library of Zurich dating from late 19th century and probably produced in Skopje contain the degrees of the houses, and after testing a number of methods I came to the conclusion that an astrolabe was used to calculate the positions of the houses. This would be a very late use of an astrolabe for real astronomical practice. ChB: What do you think about this project on astrolabes in medieval Jewish society? JTH: This is a real desideratum. There are substantial studies on the impact of the astrolabe in Latin Europe. There are many studies on the astrolabe in Muslim societies.

Therefore, investigations on the role of the astrolabe in Jewish society are likely to provide precious insights into the practice and teaching of science in general and the way scientific concepts travelled across linguistic and religious boundaries in particular. Astrolabes are very condensed pieces of information and strongly linked both to astronomical theory and its practice. In their design they are part of the tradition of material culture and, at the same time they are an offspring of scholarly literature. In that sense, the astrolabe is a unique topic in cultural history and deserves more attention. Thanks for this Johannes! Reply Ma’aseh kli ha-habatah, attributed to Ptolemy, Comunità ebraica di Mantova, 15th century. The research project ‘Astrolabes in medieval Jewish society’ has now been running for more than two years and has already proved to be a ground breaking and exciting research with active presence in several international scientific meetings and several publications on their way. The strength of this project was and is to approach two kinds of fascinating and complex medieval objects: Jewish astrolabes and Jewish manuscripts on astrolabes. For any outsider these two objects look materially disparate, but they are clearly approachable in several aspects.

First of all they are the product of the medieval mind in the fields of astronomy, cosmology, and metal work. Astrolabes are scientific instruments and medieval manuscripts describe how to make and how to use them, so the strategy of the project is to compare the extant Jewish astrolabes to what is said about these astronomical instruments in the extant Hebrew manuscripts. This comparison should provide us with information about both astronomical knowledge and metal craftsmanship among Jews, the two skills that were essential to make functional astrolabes. Our second (but by no means secondary) task is to use all the data we can extract from manuscripts and instruments to build a general picture of how and why medieval Jews became interested in astrolabes and the contexts in which they used them and wrote about them. There are about twenty astrolabes with Hebrew script written on them, a clear sign that Jews used them at some point. These instruments are all western astrolabes, i.e. they were made in Europe and northern Africa.

Some of them are European (Latin script with additions in Hebrew), some are Islamic astrolabes from Islamic Spain and Sicily (Arabic script with Hebrew additions), and just a few are completely Jewish (Hebrew and Judaeo-Arabic scripts). They are multicultural and, often, bilingual, or even trilingual, as medieval Jews frequently were. None of these instruments has a clear history (they are mostly unsigned and undated). It seems that a few of them were made by Jews, but all of them were in the hands of Jews at some moment and their Jewish owners or users wanted to leave in the object a clear indication of its Jewish relation. Frequently, the Jewish input is confined to the names of the months and the signs of the zodiac engraved on the back of the astrolabe and on the rete, or the names of some city and the number of latitude inscribed in Hebrew on some of the plates. The oldest astrolabe in our research is a western Islamic astrolabe from the twelfth century that was made in al-Andalus. However, the Hebrew script was engraved later, we do not know when or where. The same applies to most of the Jewish extant astrolabes.

From the mixture of scripts, geographical backgrounds, and disparate owners and makers a question arises regarding these objects: on what basis can we label these instruments as Jewish? We are dealing with scientific knowledge, local art, cultural traditions (which are also religious traditions), and ultimately with national cultures and identities. The definition of Jewish was as complex in Middle Ages as it can be today. Jewish astrolabes raise questions amongst historians of art and science concerning the interface of the three major cultures of Middle Ages (Judaism, Christendom, and Islam) and the customary role of medieval Jews as merely intermediaries between the East and the West. If we look at the manuscripts (about one hundred in Hebrew and a few in Judaeo-Arabic, Castilian, and Judaeo-Spanish) the information they provide is richer and broader. Here we have names, but also descriptions, signatures, sources, and dates. We read manuscripts written and copied by Jews and for Jews throughout eight centuries and find ourselves in the heart of a living culture that was Jewish and felt Jewish. These hand-written texts somehow disambiguate the puzzlement that the instruments display in relation to their identification as Jewish cultural objects.

The oldest manuscript is mid-thirteenth century, but the history of the astrolabe in Hebrew literature starts earlier, in the twelfth century in Provence, in connection with the emigration of Jews from the Iberian Peninsula, and maybe earlier: a Judaeo-Arabic fragment from the Cairo Genizah might be the oldest testimony of the use of astrolabes in Jewish culture. There are original texts and translations into Hebrew of treatises on the astrolabe written in Arabic and Latin. The manuscripts come from all around the world, for they were copied from the twelfth century until the nineteenth in Benevento, Mantua, Syracuse, Vienna, Central Europe, Istanbul, Baghdad, Egypt, and Yemen, among many other places. The treatises have been copied not only with astronomical texts but also with astrological handbooks, monographs on geomancy, medical treatises, and books on talismans, which suggest that astrolabes were used not only in astronomical contexts, but also for astrology, medicine, and magic. The culture around the astrolabe was multilingual, multicultural, and multifaceted, and still Jewish. Sometimes the researcher cannot avoid thinking in terms of a detective story.

For instance: why would twelfth-century Jewish scientists care about astrolabes for the southern hemisphere when it was commonly accepted that the inhabited lands were all placed in the northern hemisphere? Why would an unknown hand have crossed out the names of the zodiac inscribed in Hebrew in the back on an Andalusian astrolabe in such a precise and specific way that the Hebrew characters could not be read? Jewish astrolabes certainly deserve a good novel, but for the moment they are the object of devoted and careful research at the Warburg Institute. Reply TODAY PETRA G. SCHMIDL Petra G. Schmidl ( ~homepage/Islamwissenschaft/Schmidl/ ) is an expert in pre-modern astronomy and astrology in Islamicate societies, mainly interested in the interacting of astronomy and politics, astronomy and religion. Another major point of her interests concerns astronomical instruments, in particular astrolabes as a source for the history of astronomy and astrology. She is research assistant at Bonn University and currently a visiting fellow at Erlangen-Nürnberg University (International Consortium for the Research in the Humanities).

A year ago, I met Petra in Frankfurt and she introduced me to the rich archive of the former Institute for the History of Science at Frankfurt University, which has been instrumental for my research. I also met in Frankfurt David King, the leader expert on medieval astrolabes, and Benno van Dalen, who is now working on a research on Ptolemaeus Arabus et Latinus, a project dedicated to the edition and study of the Arabic and Latin versions of Ptolemy’s astronomical and astrological texts. All three were very helpful at the initial stage of my research. JRA: How did you become interested in this instrument? PSh: In seminars held by Professor David King at the former Institute for the History of Science at Frankfurt University, Germany, I first learned about astrolabes. From the beginning, still being an undergraduate student, I was completely fascinated by these instruments and their use. The unique combination of science, history, and arts as reflected in the astrolabes arouse my curiosity. I became eager to learn more about their use, their history, and their historical context. JRA: How many astrolabes are there in the world and where do they come from?

PSh: In 1932, Robert T. Gunther described in his “Astrolabes of the World” 336 astrolabes. Most of them are preserved in the rich collection of the Museum for the History of Science in Oxford, whose curator he was. In 1973, Derek de Sola Price et al. counted in their “Computerized Checklist” astrolabes, mariner’s astrolabes, and astrolabic quadrants up to 4000 (with gaps in the numeration). The preliminary Frankfurt catalogue initiated by David King back in the 1990s describes around 800 astrolabes. Approximately, four sevenths are of Eastern, three sevenths of Western provenience (The descriptions of later astrolabes, after ca. 1500, are incomplete; Until today, astrolabes are made for museum, collections, and others interested in these instruments. Only a few astrolabes display Hebrew inscriptions or additions in Hebrew script. JRA: Why and how did Muslims introduce the astrolabe into history?

PSh: Reasons of the Muslim interest in the astrolabe are difficult to name. Was it a general interest in the heavens? Was it a specific interest in timekeeping and orientation? Was it one of the other reasons, why people practice astronomy? Probably, the astrolabes’ decorative and mysteriously looking appearance may be another reason. However, first evidence of the Muslim interest in the astrolabe becomes obvious in the earliest instruments preserved from 8th- and 9th-century Baghdad, and in the oldest Arabic texts on the use of the astrolabe, e.g. al-Khwarizmi’s treatise (Baghdad, b. ca. 800). Were Muslim scientists the inventors of astrolabes? Muslim scientists – i.e. scientists living in the Islamic realm – were rather the promoters and developers of the astrolabe than their inventors. The textual evidence clearly demonstrates that the astrolabe has its roots in Greek traditions. The texts by John Philoponos (Alexandria, d. ca. 570) and Severus Sebokht (Nisibis, Kennesrin, b. ca.

575) were one way, though definitely not the only one, the Muslim scientists learned about the astrolabe. JRA: Why were astrolabes so popular among Muslims and non-Muslims? PSh: Astrolabes hang in the office of Albus Dumbledore, the headmaster of the “Hogwarts School of Witchcraft and Wizardry”, in the film called “Harry Potter and the Chamber of Secrets”. Apparently, the combination of beautiful decorativeness and sophisticated sciences makes the astrolabe so popular. JRA: Can you tell us what kind of artefact is an astrolabe and if there are different kinds of it? PSh: Astrolabes are multi-functional and multi-purpose astronomical devices. They can be used for observation, calculation and teaching, for amusement, decoration, and representation. To to put it short: The astrolabe is a two-dimensional model of the three-dimensional world that you can hold in your hand and put into your pocket. JRA: Why are there so many fake astrolabes and what would be the definition of a fake astrolabe? PSh: Probably, the question is easier to answer when beginning at the end.

In my view, a fake astrolabe pretends to be “something else”, for example, to be older, to be related to a more famous person, or to be functional (although it is not). Probably, the huge interest in the instrument urges the production of modern replica – and of fake astrolabes. ‘Fake’ Jewish astrolabe in a private collection in Tel Aviv, which I studied in August 2013. Two features of ‘fake’ astrolabes -either Jewish or not- are apparent: they are not calibrated (which implies that if there are divisions they do not make sense at all) and the engravings on all the surfaces are particularly decorative. JRA: What do you think about this project on astrolabes in medieval Jewish society? PSh: Astrolabes are a great, though rather underestimated sources for the history of science. The project “Astrolabes in Medieval Jewish Society” is important because it takes into account both texts and instruments. It demonstrates clearly the advantage of using recourse on both types of sources. Thanks for this, Petra! Reply TODAY DR. SHLOMO SELA Dr.

Shlomo Sela is a lecturer in the Departments of Jewish Thought at Bar-Ilan University (Israel). His research focuses on Jewish attitudes toward the sciences, with special interest in the history of astrology in the Middle Ages. He is an expert in Jewish astrology, notably Abraham ibn Ezra’s astrological treatises, which he is editing and translated for Brill. Plate with the divisions of the twelve astrological houses and latitude scratched in Hebrew (Science Museum, London) JRA: What can be the interest of studying medieval astrology and more specifically Jewish medieval astrology? ShS: Horoscopic astrology was most probably invented in the late second or early first century BCE, on the basis of Aristotelian physics, Greek cosmology, and Hellenistic astronomy, although it also drew on elements from ancient Babylonia and Egypt. Thus, studying medieval astrology affords a golden opportunity for both scholars and laymen interested in the history of science to observe how the achievements of these branches of Greek science were received, assimilated, applied and developed further in medieval societies and cultures.

Jewish medieval astrology is only one case of the aforementioned cultural phenomenon, and for students of the history of science its study is as interesting and fascinating as the study of its reception in the Arab and Latin medieval worlds. However, studying Jewish medieval astrology arouses an intense interest for those particularly interested in Jewish history and culture, mainly because it provides a golden opportunity to ascertain how a traditionalist and conservative culture was transformed by the reception of Greco-Arabic science without losing its religious and national identity. JRA: What were the relations between astronomy and astrology in the Middle Ages? ShS: After the rise of Greek science, it is almost commonplace to refer to the close collaboration between astronomy and astrology. Since the practical uses of learned astrology depended heavily on the mapping of the movements and relative positions of the heavenly bodies, it is clear that, on the one hand, horoscopic astrology could develop only after the growth of mathematical astronomy and, on the other hand, that astrology provided a constant stimulus to mathematical astronomy to continue to refine its tools. In addition, the fact that some ancient and medieval prominent scientists grouped astronomy together with astrology in their works highlights their interdependence.

In the Middle Ages, a good example of the close collaboration between astronomy and astrology is found in the contents of astronomical tables: along characteristically astronomical topics, such as tables of the mean motions, equations, and true positions of the moon, sun and planets, one may also find typically astrological topics such as tables for casting the 12 horoscopical places at specific terrestrial latitudes, tables of excess of revolution and revolution of the months used in continuous horoscopy, and tables of the planetary astrological ‘nature’ associated to fixed stars. JRA: Were medieval Jews more interested in astrology than their Muslims or Christians contemporaries? ShS: This is very difficult to ascertain, and my guess is that Jews were as concerned with astrology as Muslims or Christians contemporaries, and for similar reasons: in an age of extreme insecurity and uncertainty, astrology provided a system of doctrines which, using the state of the art in Greco-Arabic science, claimed to explain and predict human events related to both individuals and collectives. JRA: Is the astrolabe an instrument characteristic of astrologers?

ShS: One of the main topics of medieval manuals on the astrolabe is to enumerate and explain the functions that this instrument is intended to carry out. Judging by these functions, the astrolabe was a typically astronomical instrument. However, one may also find typically astrological functions, such as the calculation of the cardines and the twelve places of the horoscope or the calculation of the astrological aspects, which are essential and indispensable for the praxis of the astrological métier. From this specific perspective, the astrolabe was an instrument characteristic of astrologers. JRA: How was astrology accommodated to Jewish culture religion in the middle ages? ShS: The smooth absorption of astrological content into the hard core of Jewish culture was carried out in two ways: on the one hand, via the incorporation of astrological ideas into the exegesis of classic authoritative Jewish texts, such as the Bible, and, on the other, by the creation in the twelfth century of a comprehensive corpus of Hebrew astrological textbooks that address the main systems of Arabic astrology, thereby providing Jewish readers with access to astrology.

From the vantage point of Jewish religion, astrology was seen by opponents of astrology as canceling out the rewards coming from the observance of religious prescriptions, since if individual or collective fate is determined by the stars, it is hard to see how one could maintain an assumption of reward and punishment which would justify the observance of religious commandments. To counteract the utterly deterministic character of astrology, Jewish medieval sympathizers of astrology highlighted the possibility of deliverance from the influence of the stars by virtue of a singular marriage between faith and wisdom: total salvation from the stars occurs when the wise soul of man, after a process of intellectual betterment and religious devotion, departs from his body and enters into conjunction with the glorious God. JRA: What do you think about this project on astrolabes in medieval Jewish society? ShS: As Jewish medieval interest in the astrolabe epitomizes the reception of Greco-Arab science into Jewish medieval society, and because this topic is one of the most neglected parts in recent scholarship research focused on Jewish medieval science, the project on astrolabes in medieval Jewish society is in my opinion of enormous importance.

JRA: What main question/s do you think the researchers working in this project should explore or should try to answer? ShS: After cataloguing, as far as possible, all the extant works composed by Jews in Hebrew (and other languages) on the astrolabe in the Middle Ages, these are some of the questions that in my opinion should be explored: How were these manuals on the astrolabe organized and shaped? Are they essentially the same or in some way different from medieval Arab or Latin manuals on the astrolabe? On which scientific sources did the authors of these manuals draw? Which original contribution, if any, did these texts make? Are there any special features which reveal the authors’ unique contribution and special personality? What linguistic strategy did the authors of these works adopt when faced with the need to create a new Hebrew scientific vocabulary about the astrolabe? How may be explained this enduring Jewish interest on the astrolabe during the Middle Ages and this continuous stream of Hebrew compositions on the astrolabe? Thank you, Shlomo. This has been an illuminating interview! Reply TODAY PROF.

CHARLES BURNETT Charles Burnett ( ) is Professor of the History of Islamic Influences in Europe at the Warburg Institute (University of London) and is part of the research group working on astrolabes in medieval Jewish society. He is an expert in the diffusion of Arabic knowledge into Latin and is also interested in the role of Jews as mediators in this transfer. He has an impressive record of publications on the subject of this transmission and its cultural context, as well as editions and translations of several of the key manuscripts involved in the amazing transfer of knowledge and ideas that took place in western Europe. Our question for him is to explain the cultural context in which astrolabes emerged in Europe. This is his answer: We have the first indications of the introduction of the astrolabe into Christendom towards the end of the tenth century in Catalonia, the provenance of the earliest astrolabe to be inscribed with Latin inscriptions, and of the earliest Latin texts. These were based on Arabic texts, some of which have been identified.

But a Latin scholar added an elaborate preface, which, after emphasising the importance of the knowledge of astronomy, advertises the significance of the new instrument—the astrolabe–in the following words: ‘Among the other famous instruments of this art provided by him (Ptolemy), he invented a certain instrument, both most useful for learners and a great miracle for those looking at it, than which among all inventions nothing is more eminent for the intimate investigations of doctrines and the arts of mathematics, and nothing is more useful for investigating the whole of that higher machine and for all astronomical studies and the science of geometry. It is the Wazzalcora, obtained by a divine mind, which in Latin means “flat sphere”, which also by another name is called “the astrolabe of Ptolemy”. In this Wazzalcora, the whole form of the celestial sphere is described by a natural reasoning according to the roundness of the sphere, and all things are noted correctly by the architectonic reasoning of celestial figurations, which I will describe a little more clearly afterwards. How useful this is, both what follows will demonstrate and the truth of the matter will prove’.

From this time onwards the astrolabe gained a prominent place in Western European science, as a teaching instrument, as an instrument of observation, and as a symbol of the universe, and of the power of the ruler who owned that symbol. Adelard of Bath addressed a work on the astrolabe to Henry Plantagenet (the future King Henry II of England), pointing out that it was a guide to the universe; for just as the householder should know the house that he lived in, so the dweller in the universe should know his dwelling place, or else be cast out of it. Peter Abelard and Heloise named their son ‘Astrolabius’, perhaps as an indication that he pointed the way to the heavens. Works on the construction and use of the astrolabe featured prominently in the translation programmes from Arabic into Latin of the mid-twelfth century. Through the astrolabe the positions and the names of the most prominent fixed stars in the sky became known. No astronomer or astrologer could be without his astrolabe, and even the schoolboy was expected to know how to use the instrument, as we see from Chaucer’s English text on the astrolabe addressed to his son Louis.

(Sources: José-Maria Millàs Vallicrosa, Assaig d’història de les idèes fisiques i matemàtiques a la Catalunya medieval, Barcelona, 1931; Arianna Borrelli, Aspects of the Astrolabe, Stuttgart, 2008; Geoffrey Chaucer, A Treatise on the Astrolabe Addressed to his Son Lowys A.D. 1391, ed. W. Skeat, London, 1872). From now on we intend to post regular short interviews with experts in the fields of the history of science, Jewish history, Jewish science, and astrolabes, the fields in which our research project fits. TODAY PROF. SILKE ACKERMANN Prof. Silke Ackermann ( ) has been a curator at the British Museum for more than fifteen years, period in which she was in charge of the scientific collections (among them astrolabes). Whilst she was working at the British Museum Silke got involved in setting up the Jewish Astrolabe project and participated as co-investigator.

However, her new job as president and professor of the Baltic College (in which she has introduced a MA in Cultural Tourism) separated her from her initial role in our project. Nevertheless, she remains interested in this research and is a member of the board of advisors. Thus Prof. Ackermann and the researcher of the project, Dr. Josefina Rodríguez-Arribas, studied together in August 2012 one of the astrolabes considered in this research (a 11th century Muslim astrolabe with Hebrew inscriptions preserved in the Staatsbibliothek zu Berlin – PK). It is a great pleasure to count on her experience and expertise with scientific instruments. For this reason, we have decided to start this new section of our blog with her. Detail of the back with Hebrew inscriptions of the Andalusian astrolabe at the Staatsbibliothek zu Berlin – PK JRA: What is an astrolabe? Were astrolabes common objects in the past? SA: An astrolabe is one of the most sophisticated instruments ever constructed before the invention of the computer – and at the same time it is relatively easy to use.

Basically it is a two-dimensional projection of the three-dimensional celestial sphere – similar to a map being a projection of the earth. It can be used in many different ways, for example to tell the time during the day and at night-time, to estimate the time of sunrise and sunset, to determine the time of prayer in the Islamic World, to make certain astrological predictions, to measure angles etc. etc. to name but a few of the manifold uses. About a thousand astrolabes are known to have survived, many more will have been constructed according to treatises written in various languages from Greek and Latin to Arabic and Hebrew as well as English, French, German, Spanish, Italian and others. They were mostly made of brass and thus very costly (and thus very special) at the time, but we also know of designs for instruments that could be cut from paper and then pasted onto card or wood – a kind of make-yourself version. These will have been more common and used by different people for various functions. JRA: There were many scientific instruments before the Scientific Revolution of the 17th century. Can you mention some of them for our blog? What is distinctive of astrolabes in relation to all of these instruments?

SA: If one looked at astronomical instruments alone or even just time-keeping instruments there were, indeed, quite a number before the Scientific Revolution such as sundials of virtually infinite designs, quadrants and nocturnals to name but a few. The intriguing feature of an astrolabe is that it combines so many functions and that its basic designs remained virtually unchanged for nearly 2,000 years. JRA: Why are there astrolabes engraved with different languages? Leaving aside the languages, are there other differences among the extant astrolabes or all of them are similar except for the script? SA: Astrolabes are truly cross-cultural. The ancient Greeks are credited with the invention of the instrument (or rather: with the discovery of certain mathematical principles that allowed its construction). But the instrument was further developed and used by virtually all cultures that came into contact with it. This is why so many different languages can be found on one instrument, such as the star-names in Arabic or a Latinized forms of Arabic (or a vernacular thereof) of even different languages together when an instrument was for example made in the Islamic World and later used by a Latin scholar who may have added some features in Latin or another who added Hebrew markings.

The different languages often tell us the most intriguing stories about an instrument’s history. There are certain basic features every astrolabe possesses – but many features can be added or omitted at will. Additionally astrolabes can be of the most intricate design and a pure joy to behold – which must be one of the reasons why so many have survived even at a time when they were long out of use. They are just utterly beautiful and from very early on became collectors’ pieces. JRA: Astrolabes seem to have been known in Europe, Northern Africa, the Near East, and India. Did other cultures like the Far East or pre-Colombine America have astrolabes or similar objects? SA: I have so far not come across genuine instruments from the Far East or pre-Columbian America, but that does not mean that they do (did) not exist. JRA: You have been a curator of scientific instruments at the British Museum for many years and now you are teaching at the Baltic College in Schwerin (Germany). What is the interest of studying astrolabes (pre-modern instruments) in the 21st century? Are you able to bring the subject of astrolabes and their historical background into class?

How? SA: In my current role at the University of Applied Sciences at Schwerin in North-East Germany I have so far had very little opportunity to discuss astrolabes. But I am trying to introduce students to the role of objects as historical sources on a par with written documents. The study of astrolabes enables us to bring long-gone periods such as the Middle Ages or the Renaissance to life, to shed a light on the in-depth knowledge of astronomical and mathematical features and on the intercultural exchange that took place. JRA: We know that you are also very interested in Jewish astrolabes. Your interest in Judaism, where does it come from? What has Judaism to do with astrolabes? SA: I have always been interested in history and in the sharing of knowledge and ideas between the three great religions of the book (namely Judaism, Christianity and Islam). I am fascinated by the way in which cultures influenced by one or more of these religions used, adapted and developed this intriguing instrument – and how the instruments and related texts mirror the thought-processes behind this exchange.

For many years I have researched the exchange of ideas in the Middle Ages and the Renaissance and it became increasingly clear to me how little I actually knew about the role Jewish scholars had in this process of transmission. JRA: As an expert in scientific instruments, what is the question about astrolabes and Jews that any serious research on the subject should answer or inquire into? SA: When I first suggested a research project on the role of the astrolabe in Jewish communities in the Middle Ages it was born out of a certain frustration that I could find so little information in my sources and in the literature on what this instrument actually meant for these communities, how it had been used and why and by whom. If the outcome of the project manages to answer some of these questions I would be thrilled. Thank you! Reply Posted by Josefina Rodríguez Arribas We are trying to trace the following astrolabes with Hebrew script or a Jewish maker (see list below). They are fundamental for our research so we would be very grateful if someone can provide any information about them (the #number refers to David King’s inventory of astrolabes).

1– Private astrolabe (last owner in Morocco, #1122) An astrolabe by Ya’qub ibjn Musa Tapiero supposedly dated 716 H (but more probably 1016 H). Morocco, private collection. Formerly in the Duval Collection (according to Mayer). This astrolabe is signed by a Jewish astrolabist. 2– Private astrolabe (last owner in Palermo, #4590) An astrolabe of uncertain date and provenance with Maghribī Arabic and additional Hebrew and Latin inscriptions, different from the instrument in the Biblioteca Comunale. 3– Private trilingual astrolabe unknown place (#4560) Quatrefoil ornamentation, inscriptions in Latin, Arabic and scratches in Hebrew on several plates. 4– Private bilingual astrolabe, unknown place (#4520) A fourteenth-century European astrolabe with Hebrew additions. On the back of this instrument the Hebrew names of the signs and months have been added in an inelegant hand.

5– Private trilingual astrolabe, unknown place, sold in London in Sotheby in 1986 (#4509) Trefoil and semiquatrefoil decoration. An astrolabe with elements of different provenance, one of the plates is inscribed in Greek. Latin and Hebrew script. Sold in Sotheby in London in 1986 (Sotheby’s London 18.6.1986 Catalogue, p. 24). See below a picture showing the front of this astrolabe (picture by courtesy of the former Institute for the History of Arabic-Islamic Science at the Johann Wolfgang Goethe University, Frankfurt am Main). 2 Posted by Josefina Rodríguez Arribas Our group of research organized a Symposium related to Jewish astrolabes in the International Conference of the European Society of History of Science in Athens (1-3 November 2012). Several experts in the fields of astrolabes and medieval astronomy, astrology, and calendar were invited to present papers about their fields.

This is the program: The scientific culture of medieval Jews: facts and questions This symposium considered what role science played in the culture of the Jews of the Middle Ages in the Islamic and Western European contexts. It focused on astronomy: the use of astrolabes and other astronomical instruments, the texts composed on their manufacture and use, the composition of astronomical tables, the writing of theoretical works on astronomy and cosmology, and the application of astronomy to the practice of astrology. The social and religious context of this pursuit of science was explored.

Participants: 1 Tzvi Langermann: Abraham Bar Hiyya’s Megilat ha-Megalleh: An Early Integration of Philosophy, Astrology, and Theology 2 Shlomo Sela: Abraham Ibn Ezra and the Astrolabe 3 Charles Burnett: Abraham Ibn Ezra’s Latin-Reading Pupils 4 Sreeramula Sarma: Asturlâb and Yantrarâja: Two Parallel Traditions of the Astrolabe in India 5 Josefina Rodríguez Arribas: Hebrew Manuscripts on the Astrolabe: a Preliminary Overview 6 Ilana Wartenberg: Mathematical Elements in the Jewish Calendar During our stay in Athens there was plenty of time for reading and listening to papers, meeting scholars of all around the world, and participating in interesting discussions. The picture below shows the scholars of our session before Heinrich Schliemann’s house in Athens just on our way to the conference dinner. From left to right: Charles Burnett, Sreeramula Sarma and his wife Renata, Ilana Wartenberg, Johannes Thomann, Shlomo Sela and his wife Leah. Below, part of our group in the site of the Academy of Plato.

The Mariner's Astrolabe ASTROLABE The Mariner's Astrolabe The Mariner's Astrolabe was used to determine the latitude of a ship at sea by measuring the noon altitude of the Sun or the meridian altitude of a star of known declination (photo courtesy Adler Planetarium and Astronomy Museum). It was not possible to determine longitude at sea in the early days of transoceanic navigation, but it was quite easy to determine latitude. To go to a place of known latitude, the ship was sailed to that latitude and then sailed east or west along the latitude line until the place was reached. To find the latitude of the ship at sea, the noon altitude of the Sun was measured during the day or the altitude of a star of known declination was measured when it was on the meridian (due north or south) at night. The Sun's or star's declination for the date was looked up in an almanac. The latitude is then 90° - measured altitude + declination . A number of devices were used to measure the Sun's noon altitude. Among them were the quadrant, cross staff and, later, the back staff and the mariner's astrolabe.

All these devices had a single use: to measure the altitude of a celestial body above the horizon. The Mariner's Astrolabe, which was popular in the late 15th and early 16th centuries, was a simple brass ring, graduated in degrees with a rotating alidade for sighting the Sun or a star. The ring was cast brass, quite heavy and cut away to keep it from blowing around in the wind. It was not a very good instrument and errors of four or five degrees were common. It should be noted that any instrument used to measure altitudes above the horizon can be called an astrolabe. The term astrolabe is often used in a context that is not the same as the classic planispheric astrolabe. A Portugeuse mariner's astrolabe was found in Newfoundland in 1981, by Wayne Mushrow . You can download a template for making your own Mariner's Astrolabe. The template consists of a Word for Windows 6.0 document with basic instructions and a PostScript file that can be printed containing the outline of an instrument. The astrolabe in the template is eight inches in diameter.

Click here to download the template as a self extracting zip file (mariner.exe 51K). To expand the downloaded file into the instructions (mariner.doc) and the template (mariner.ps) simply execute the downloaded file (mariner.exe). The mariner's astrolabe in the template is shown below: An example of a mariner's astrolabe made from this template is shown on the page of astrolabes made by individuals . Who Created an Astrolabe? In-depth Astrolabe History and Information on Its Structure and Uses Who Created an Astrolabe? written by: Anurag Ghosh•edited by: George Adcock •updated: 1/12/2010 Call it the ancient astronomical “laptop computer" or a “mini-planetarium", the astrolabe was one of the best astronomical inventions of the ancient era. Nevertheless, we always wonder who created an astrolabe and what were its important uses? Here are important uses and history of the astrolabe. slide 1 of 5 The Astrolabe: Meaning and Key Uses An astrolabe is a multipurpose astronomical model of the celestial sphere that once was used by ancient and medieval astronomers.

This portable ancient astronomical “lap-top computer" of the ancient era had several uses. Astronomers used the astrolabe to determine the positions of the sun and stars and corrected various celestial miscomprehensions. It was one of the most innovative mechanisms in the Hellenistic world, but today, many people wonder who created an astrolabe? The astrolabe consists of a disc-shaped piece of metal or wood suspended by a ring. The face of the circular metal has equator, tropics and 24 divisions of time engraved on it, with a celestial pole at the center of the circular metal plate. On the reverse, several circles with different gradations are engraved. The different circles with gradations represent months, days etc. Before we delve deep into the astrolabe history, let us first understand its different uses. Ancient astronomers used this small ingenious mechanism by setting moveable gears to a specific date and time.

Once the settings were adjusted, the astrolabe provided accurate measurements of the entire sky such as: The position of the sun, moon and other heavenly bodies The accurate time of the celestial event (sunrise, sunset, phases of the moon etc, the astrolabe was also used as a portable sundial) Determine latitude & longitude and measure the altitude The astrolabe was also used in surveying, navigation and triangulation (trigonometry/geometry). Some medieval astronomers even used an astrolabe for astrological purposes. slide 2 of 5 Who Invented the Astrolabe? The multipurpose 2D mechanical replica of the celestial sphere has a deep history behind its invention and use. The astrolabe stems from the Greek words astron meaning star and lambanien meaning to take. It was created about two thousand years ago, whereas concept of astrolabe projections was known before 150 B.C. However, the creation of the first astrolabe is attributed to the Greek astronomer and mathematician Hipparchus. The brilliant astronomer invented this mechanism around 200 BC. While the first Hipparchus-invented astrolabe was basic, complex astrolabes gained recognition after 400 AD.

In around 800 AD, eastern Christian scholars (Greek or Syriac-speaking astronomers) introduced the concept and diagram of astrolabe to the Arab world. Later, in the medieval period astrolabes were specifically used as a navigating device to find the location of Kaaba in Mecca. It was also used in diverse areas such as astrology, navigation, timekeeping and horoscopes. During the middle ages, the astrolabe saw several transformations and variations, including the popular spherical astrolabe and linear astrolabes created by inventors and astronomers of the Islamic world. In the fifteenth century, metal astrolabes began gaining popularity and were used by serious and amateur astronomers. The first metal astrolabe was created by Rabbi Abraham Zacuto in Lisbon in the fifteenth century. slide 3 of 5 Conclusion The credit for the invention of the earliest astrolabe goes to Hipparchus, who created an astrolabe in its crudest form but gave the medieval world an important mechanism to understand the celestial sphere more accurately. Even today, different types of astronomical astrolabes are available for students to identify the functioning and uses.

There are also several websites such as homesciencetools.com and the center for science education that provide kits and helpful how-tos on creating a personal astrolabe. slide 4 of 5 The Mariners' Museum | EXPLORATION through the AGES Marinerï¿½s Astrolabe, Portuguese, 1645, by Nicholao Ruffo, The Marinersï¿½ Museum, (2000.52.1) Astrolabe One of the oldest of all the altitude measuring devices, the Astrolabe is an angle-measuring tool thatï¿½s name comes from the Greek, "to take a star." It was possibly invented by the Greek astronomer and mathematician, Hipparchus (190-120 BCE ). However, in its earliest uses, it was for astronomy and astrology. Only when the need to measure angular heights of Polaris became important did we see these instruments adopted for sea-going use. As an astronomer's tool, the Astrolabe was introduced to the Europeans by Arab astronomers in the 10th century, CE .

But the first documented use of it used at sea is in 1481 on a voyage down the African coast by Portuguese explorers. It is likely, though, that it was in use by sailors for many years before that. Using an astrolabe, Le Novveau Phalot de la Mer, 1635, From The Library at The Marinersï¿½ Museum, VK801.J35.1635rare. So how does it work? To correctly measure the angle of the sun or a star, the Astrolabe must hang down so that it is perpendicular to the ocean. If it's tilted right or left, or front to back, the angle will not be accurate. To keep it straight, the user holds it with a finger through a ring and lets the Astrolabe dangle. Next, take a look at the diagram and see that there are two plates on a rotating arm. They each have a pinhole perfectly lined up so that when the sun shines through the top one, and hits the second pinhole, the angle is accurate. You then read from the scale along the circumference. For Polaris , you can sight over the edge of the two plates.

One advantage of the Astrolabe is that you do not need a clear horizon to use the instrument; you do need a clear horizon when measuring the height of the sun or Polaris with other navigational instruments. Astrolabe, A New Collection of Voyages, Discoveries and Travels: Containing Whatever is Worthy of Notice in Europe, Asia, Africa, and America, 1767, From The Library at The Marinersï¿½ Museum, G160.K75 rare. It is not a particularly accurate tool at sea because of the difficulty in keeping it steady in a rolling ship and high winds. Usually, however, the Portuguese explorers would take their Astrolabe ashore and set it up to avoid this problem; this is what they did when they were mapping the coast of Africa in their early exploration. Using it at sea could result in errors as much as five degrees, or 300 miles. However, ashore, it would be much more accurate, certainly less than one-half degree, or 30 miles.

The sea-going version might be 6" in diameter, whereas the one they took ashore (and which would be awkward to use at sea) might be two feet in diameter, making it more accurate and easier to read.

Question: An astrolabe was used for astrology, navigation and what else?
Answer: Astronomy