An Introductory History of Astrolabes

Shanna Freeman’s new post, “10 Astronomical Discoveries Made Without a Telescope” over at Curiosity.com gets a few things wrong. See Thony C’s “Discovering HistSci stupidity in the Intertubes” for a nice review of the problems in Freeman’s post. Here I am going to expand a bit on just one of the errors already mentioned by Thony C. In her opening paragraph, Freeman claims, in two different places, that the astrolabe was in use since at least 150 B.C.

As Thony C. has pointed out, there are two problems with this: First, that “instrument” in the image is not an astrolabe. It seems to be a sundial, astronomical compendium, compass thingy. It certainly could not perform any of the functions of an astrolabe. Second, the astrolabe was certainly not in use, hadn’t even been invented, in 150 B.C.

It is regrettable when a purportedly reputable source, Discovery.com and Curiosity.com get something like this wrong, particularly when a simple wikipedia search would have revealed the error. Since they couldn’t be bothered, I will try to provide a little more accurate information. What follows is a draft I wrote on the history of astrolabes.

Introduction
Early History
Medieval History
Early Modern History

Introduction—
The astrolabe was the most widely used scientific instrument in the middle ages. Nevertheless, its origins remain uncertain. The earliest surviving instruments date from medieval Islam. However, Greek and Syriac texts testify to a long theoretical and practical development that extends back to the second century BCE. The underlying mathematical principle of stereographic projection was described by Hipparchus of Nicaea (fl. 150 BCE). Less than two centuries later, Vitruvius (died post 27 CE) described a type of clock that depended on a similar stereographic projection. His suggestion that Eudoxus of Cnidos (ca. 408-355 BCE) or Apollonius of Perga (ca. 265-170 BCE) invented the rete or spider—the network of stars—almost certainly refers to the sundials he was discussing in the passage. Claudius Ptolemy (fl. 150 CE), the most famous astronomer from antiquity, wrote an extensive theoretical treatment of stereographic projection in his Planisphaerium, which included a short discussion of a horoscopic instrument. Although he described an instrument that resembles an astrolabe, including both a rete and the stereographic projection of a coordinate system, Ptolemy’s instrument does not seem to have included the apparatus needed to make direct observations and thus to measure the altitude of the sun or stars.

Early History—
As early as the fourth century authors began composing manuals on the astrolabe. Theon of Alexandria’s (fl. 375 CE) work “On the Little Astrolabe” is the earliest text to treat the construction and use and of the astrolabe. It became a model both in form and content for later literature on the astrolabe. After Theon, treatises on the astrolabes became increasingly common. Synesius of Cyrene (ca. 370-415 CE) wrote a short work on the astrolabe and mentions a silver planisphere that he sent to Paeonius in Constantinople. The Byzantine scholar Ammonius (died post 517 CE) reportedly wrote a treatise on the construction and use of the astrolabe. More importantly, Ammonius incorporated the astrolabe into his teaching, thereby introducing a number of people to the instrument. The oldest surviving treatise on the astrolabe comes from his most famous pupil, the mathematician and philosopher John Philoponus (ca. 490-574 CE). In 530 he wrote wrote a work entitled “On the use and construction of the astrolabe and the lines engraved on it.”

Philoponus’ text offers a practical description of the astrolabe and surveys its most common uses. In the middle of the seventh century, Severus Sebokht of Nisibis, Bishop of Kennesrin in Syria, wrote a description of the astrolabe in Syriac. Sebokht’s exposition conforms to the patterns established by Theon and adopted by subsequent authors. Like his predecessors, he eschewed theoretical discussions, concentrating instead on practical description and application. He greatly expanded the standard list of uses. Knowledge and production of the astrolabe spread from the Byzantine and Syro-Egyptian context east through the Syrian city of Ḥarrān and into Persia.

Ḥarrān had been an important centre of pre-Islamic translation activity. With the rise of the ‘Abbāsid caliphs came a new interest in Greek science and technology, both of which played a key role in efforts to legitimate their rule. Al-Manṣūr (712-775 CE, caliph from 754), the second ‘Abbāsid caliph, supported the translation of Greek science into Arabic and promoted various sciences, especially astronomy and astrology. Increasingly he relied on court astrologers: on their advice he selected 30 July 762 CE as the day to lay the foundations of Baghdad; he consulted with them when his relatives revolted; and they accompanied him on his pilgrimages to Mecca. In this context the astrolabe was a useful tool. Al-Manṣūr’s great grandson, al-Ma’mūn (787-833 CE, caliph from 813) consolidated and extended this policy. In addition to their political uses, astrolabes had immediate religious applications. The close connection between astronomy and Islam provided an obvious incentive for developing the astrolabe. Finding the times of the five daily prayers as well as the direction of Mecca are both complicated astronomical and geodetic operations. Makers quickly perfected techniques that made it possible to determine through direct observation both the time of prayer and the direction of Mecca.

Over the next few centuries Arab, Persian and Jewish scholars produced numerous systematic treatises on the astrolabe. The earliest of these was written by Messahalla, a Jew from Basra, whose work dates from before 815 CE. The original Arabic treatise has been lost, but numerous Latin translations of it survive. The oldest surviving Arabic treatises date from the early ninth century. Al-Kwārizmī (fl. 825 CE) wrote two short texts, one on the construction and one on the use of the astrolabe. Other early texts by ‘Alī ibn ‘Īsā (fl. 830 CE) and Aḥmad ibn Muḥammad ibn Katir al-Fargānī (fl. 857 CE) also survive. Along with his treatise on the astrolabe, ‘Alī ibn ‘Īsā made various astronomical observations in Baghdad and Damascus under the patronage of al-Ma‘mūn. In the early eleventh century al-Bīrūnī (973–1048 CE), a Persian scholar, wrote his Book of Instruction in the Elements of the Art of Astrology, which included detailed descriptions of the construction, parts and uses of the astrolabe. During this same period, making astrolabes developed into a well respected profession. Arab craftsmen developed their skills and tacit knowledge, creating family workshops that continued for a number of generations. The oldest surviving astrolabes date from this period of intellectual efflorescence supported by the early Islamic caliphs.

Traveling Persians scholars like al-Bīrūnī probably introduced the astrolabe to the Hindus quite early, and later scholars brought astrolabes to the court in Delhi. During the fourteenth century, the Sultan Fīrūz Shāh Tughluq (1300-1388 CE, reigned from 1351) sponsored the manufacture of astrolabes. The first Sanskrit treatise on the astrolabe, entitled Yantraraja (“King of astronomical instruments”), was written in 1370 by a Jaina monk, Mahendra Sūri (1340-1410 CE). Mughal India adopted the instrument with great enthusiasm in the mid-sixteenth century. The new rulers relied heavily on astrology to regulate their affairs and considered the astrolabe a valuable astrological and political tool. Contemporary chronicles emphasize Emperor Humāyūn’s (1508-1556 CE, reigned from 1530-40 and 1555-6) interest in astrolabes. Under Humāyūn’s patronage, Lahore, in present-day Pakistan, became the centre of production of Indo-Persian astrolabes. One family came to dominate the manufacture of astrolabes in Lahore, producing more than 100 astrolabes over the next century. The most prolific and famous member of this family was Ḍiyā’ al-Dīn Muḥammad (fl. 1645-1680 CE), who produced more than 30 astrolabes between 1645 and 1680 CE.

Much later, Jaipur, in northern India, developed into an important city for the production of Indian astrolabes. Jaipur’s rise to prominence corresponds to the Maharajah Sawai Jai Singh II’s (1686-1743 CE) efforts to build the great observatories in the city. Jai Singh had also written a book on the construction of the astrolabe and founded a centre for their manufacture. Indian instruments from Jaipur are often notable for their size and by the fact that they have a single plate engraved for the 27°, the latitude of Jaipur.

By the thirteenth century knowledge of the astrolabe had reached China. In 1267 Jamal al-Din brought Kublai Khan models of various astronomical instruments that were in use at the observatory in Maraghah. Marco Polo claimed to have seen astrolabes in Beijing and within a century, The Travels of Sir John Mandeville describe astrolabes at Kublai Khan’s court. Despite these reports, which are themselves problematic, the astrolabe does not seem to have been as popular in Chinese culture as it was elsewhere.

Numerous treatises testify to the importance of the astrolabe in the Byzantine Empire. Greek scholars profited from having uninterrupted access to the earliest treatises on astrolabes and composed numerous manuals on the astrolabe. Indeed, an almost continuous series of texts extend from Philoponus’ treatise in the early sixth century to Nikephoros Gregoras’ (ca. 1292-1360 CE) treatise in the fourteenth. These Byzantine manuals, especially Gregoras’, played an important role in later European texts of the sixteenth and seventeenth centuries. Surprisingly, only one complete Byzantine astrolabe, dated 1062, has been identified.

By the tenth century, astrolabe production spread west across North Africa and into Muslim Spain. In direct contrast to the history of the astrolabe in Byzantium, its history in North Africa is characterized by a wealth of instruments and dearth of texts. North African, or Maghribi, astrolabes share conservative stylistic features that set them apart from the eastern Islamic instruments. They also reveal a closer connection to Christian Europe, most notably in the presence of the Christian calendar frequently found on the back of these instruments. Although astrolabes were produced and used across North Africa, the tradition was strongest in Morocco, where they were manufactured and used for more than 500 years. By the early fourteenth century, sophisticated universal astrolabes were being produced in the Moroccan city of Taza. Along with Taza, cities like Marrakesh, Fez and Meknes became associated with both the manufacture and use of astrolabes. Muḥammad ibn Aḥmad al-Baṭṭuṭī, one of the most prolific makers from North Africa, was still producing astrolabes in Morocco as late as the eighteenth century. (See the nice if brief on-line exhibition: Astrolabes of Africa).

Medieval History—
The astrolabe was probably introduced into Muslim Spain through Cordoba, at that time the capital of the Ummayad Emirs. Scholars throughout Spain were quick to adopt the astrolabe. By the late tenth century astrolabes and manuals on their use were being produced throughout the Muslim Spain. These instruments show many similarities with those produced in North Africa. At the same time, Spanish makers developed a style that distinguished their astrolabes from the Maghribi instruments. Muslim Spain also provided an important context for the diffusion of astrolabes into Christian Europe. Arabic texts on the astrolabe were translated into Latin, making them accessible to European scholars who came to Spain looking for Greek and Arabic knowledge. Gerbert of Aurillac (ca. 945-1003 CE), who became Pope Sylvester II in 999 CE, was one of the first European scholars to establish intellectual contact between Latin Christendom and Islam. He traveled to Catalonia to complete his education and acquire books on various mathematical subjects, including the astrolabe. When he returned from Spain he probably brought with him copies Llobet of Barcelona’s (fl. late tenth century CE) Latin translations Arabic manuals on astronomy, astrology and the astrolabe and remained in close contact with Spanish scholars, requesting additional books and translations. He introduced the astrolabe to his students at Rheims. Knowledge of the astrolabe spread quickly throughout Europe. Within fifty years, a copy of Llobet’s text on the astrolabe was in the monastery at Reichenau in Carinthia, where Hermann Contractus of Reichenau (1013-1054 CE) relied on it when writing his own his De utilitatibus astrolabii.

Along with texts on the astrolabe, northern European scholars acquired actual instruments. By 1025 Rudolf of Liège could boast of owning an astrolabe, and Walcher of Lorraine (died 1135 CE), the prior of the Abbey of Malvern, used his own astrolabe to determine the time of a lunar eclipse on 18 October 1092. Between the 11th and 13th centuries, the majority of astrolabes in northern Europe were imported from Muslim Spain. Like texts, these instruments were often translated into Latin so that their new owners could understand them. For centuries Spanish astrolabes were recognized as valuable possessions and useful tools — Martin Bylica (1433-ca.1493 CE) was still using an astrolabe from Cordoba in the late fifteenth century.

Soon, manuals on the construction and use of the astrolabe became common in universities throughout Europe. Indeed, in the 1390s Geoffrey Chaucer thought it necessary to send his son of to study at Oxford with both an astrolabe and a manual on its use. For this occasion, Chaucer wrote the first English text on using the astrolabe, his A Treatise on the Astrolabe. Chaucer might have composed this work with a particularly astrolabe at hand. In any case, the text was clearly meant to be used alongside an actual instrument.

Chaucer was able to give his son an astrolabe because the instruments had become increasingly common in Europe as workshops began to form around individual craftsmen. The most famous of the early astrolabists was the Parisian Jean Fusoris (ca. 1365-1436), whose instruments were highly sought and widely copied. Fusoris was both a scholar and a craftsman as well as successful entrepreneur and convicted spy. His instruments are cleanly engraved and largely unadorned, but nonetheless elegant. He introduced a range of innovations, such as equal-hour lines on the limb and rule on the front of the astrolabe, which he had discussed in his treatise on astrolabes. Perhaps more significant for the the history of astrolabes, he was the first of the scholar-craftsmen who would come to dominate the production of instruments during the Renaissance. He set up a commercial workshop in Paris that produced astrolabes, along with clocks and other astronomical instruments. No longer were individual scholars required to make their own instruments. Instead, Fusoris and the makers who followed him combined theoretical and practical knowledge with commercial interests and established workshops that made instruments for an increasingly broad market.

Early Modern History—
Although the early trade in astrolabes centered on universities, by the fourteenth century astrolabes were increasingly collected and used by princes, kings and emperors throughout Europe. As early as the twelfth century, Adelard of Bath (fl. 1116-1142 CE) dedicated a treatise on the astrolabe to the future King Henry II of England while tutoring him in Bristol during the 1140s. Charles V of France (1337-1380 CE) owned twelve astrolabes. Martin Bylica (1433-ca.1493 CE) accompanied the Hungarian king Matthias Corvinus on military and diplomatic journeys and regularly used his astrolabe to determine propitious times to engage in battle or sign treaties. Andreas Stiborius (1465-1515 CE) created various paper astrolabes for the Holy Roman Emperor Maximilian I (1453-1519 CE), who in 1507 used one of these paper astrolabes to determine the best time to sign a peace treaty with the Hungarian King Ladislaus. Queen Elizabeth I of England (1533-1603 CE) had two astrolabes, one of which is dated 1559, the year of her coronation.

This astrolabe may have been given to the Queen by Robert Dudley, future Earl of Leicester in response to being installed as Knight of the Garter. The Holy Roman Emperor Rudolf II (1552-1612 CE) had no fewer than eight astrolabes in his collection of scientific instruments and was renowned for supporting instrument makers. One of the more prolific makers to enjoy the emperor’s generous patronage was Erasmus Habermel, who created beautiful astrolabes and other instruments for the emperor’s family as well as other princes and dukes throughout Europe.

In Europe, interest in the astrolabe peaked in the sixteenth century. Introductory texts outlining the astrolabe’s uses were produced in small, cheap formats, making them available to a broad audience. These texts offered the reader a pragmatic set of canons for the most common uses, such as telling time, determining the rising sign or drawing a horoscopic chart. At the same time, large, richly illustrated and expensive works appealed for a more select public. These texts detailed various construction techniques, offered the most current data needed to arrange the stars and presented the historical development for most uses. The most famous of these ornate volumes were produced by Johannes Stöffler (1452-1531 CE), Peter Apian (1495-1552 CE), and Andreas Schöner (1528-1590 CE), which quickly became the standard by which others were judged. Some of these texts were enlarged and reprinted while others were translated into a local vernacular and reprinted in a smaller, more affordable format. Texts written in the vernacular were quickly translated into Latin so that they could be sold to a broader audience. This publishing activity addressed only a portion of the rising interest in astrolabes.

The sixteenth century also witnessed a dramatic increase in the number of European instrument makers. The natural resources and tradition of metal working that had made the Nuremberg-Augsburg region of southern Germany the centre of instrument production in the late fifteenth century continued into the sixteenth. Makers in both Augsburg and Nuremberg benefited from the commercial interests of the Fugger family who had a monopoly on the Central European mining industry. In the first half of the sixteenth century, brass and copper were readily available in both cities but were more difficult to obtain and more expensive in other parts of Europe. It is not surprising, then, that the southern German makers had a near monopoly on the production of astrolabes and other instruments. The most famous of them was Georg Hartmann (1489-1564 CE). His “Collectanea mathematica,” written in 1527-1528, focuses on the construction of astrolabes and related instruments and testifies to Hartmann’s early interest in astrolabes. By the 1520s he had settled in Nuremberg and set up a workshop in which the various parts of astrolabes were constructed by individual craftsmen and then assembled. This enabled him to produce a large number of instruments, all of which are characterized by a pragmatic and unadorned style. He was the first person to make astrolabes by printing the component parts onto paper, which could then be glued to wood.

Scholars had previously made manuscript astrolabes, which they often affixed in their manuals. These instruments usually had only one side and were designed for specific purposes, such as casting horoscopes. Hartmann’s paper astrolabes, by contrast, were complete instruments. Because they were inexpensive, they found a ready market.

In the 1530s, the centre of production moved west into the Low Countries. The ready supplies of copper and brass provided the material needed for the Antwerp-Louvain region develop into the most important centre for the manufacture of astrolabes and related instruments. As in the cases of Fusoris in Paris and Hartmann in Nuremberg, the workshop in Louvain developed around a scholar-craftsman. Gemma Frisius (1508-1555 CE) had been educated at the University of Louvain, where he remained as a professor of medicine. Gemma set up a workshop and began making celestial and terrestrial globes. In 1552 Gemma’s nephew Gualterus Arsenius (fl. 1554-1579) started working as the engraver in the workshop. Under Arsenius’ direction, the workshop became the most important one in Europe, making dozens of astrolabes for patrons in Spain, France and England. Arsenius’s instruments are characterized by their fine craftsmanship and beautiful engraving. Astrolabes produced in Arsenius’’s workshop established a style for astrolabes and were widely copied. Thomas Gemini (ca. 1524-1591 CE), who produced instruments in London, made astrolabes in the Louvain tradition. Erasmus Habermel made Arsenius-style astrolabe while living and working at the Holy Roman Court in Prague.

In Europe, interest in astrolabes as mathematical instruments declined in the seventeenth century, Although some makers still produced astrolabes, by the early eighteenth century production had nearly stopped. During this same period, scholars increasingly collected astrolabes as antiquities rather than as instruments to be used. Both the antiquarian John Selden (1584-1654) and William Laud (1573-1645), the Archbishop of Canterbury, collected astrolabes as objects rather than instruments. The interest in astrolabes as objects had its most thorough expression and revision in the efforts of Lewis Evans in the late nineteenth and early twentieth centuries. Unlike earlier antiquarians, Evans collected astrolabes because of their importance as objects of historical significance. Consequently, he believed that they should be made available to the public and in 1924 presented his collection to the University of Oxford. Six years later Evans’s collection of astrolabes and related instruments and books were made available to the public in the newly opened Museum of the History of Science. Today, the astrolabes in the Lewis Evans Collection of Historic Scientific Instruments, many of which are on display, still form the core of the Museum’s collection of astrolabes and help make it the largest in the world.