15-16th Century Italian-Islamic Exchanges of the Astrolabe and Effects on Visual Culture
Within early modern histories of astronomy, two debilitating presumptions have dominated and disfigured the scientific narrative. One, that European and Near Eastern cultures of astronomy developed along separate, linear, non-intersecting paths, and two, that the Copernican heliocentric cosmology emerged on its own in Europe, inaugurated the Scientific Revolution, and only then traveled from West to East. These presumptions underscore the richly complex and fascinating networks of scientific exchange that were in fact very present in the early modern Mediterranean world. A mapping of this cross-cultural scientific exchange in relation to concurrent architectural activity reveals unexpected shared aesthetic ideologies and practices between the East and West. By isolating sites of exchange of the astrolabe between Ottoman and Italian courts in the 15-16th centuries, my research will illustrate the prevalence of both cross-cultural and cross-disciplinary influence.
With the expansion of empires and the setting up of trading posts in the East, scholars extensively exchanged books, manuscripts, letters, instruments, and traveled to other intellectual centers to study. Much like the trades of Persian tapestries, Illyrian and Istrian stone, Iznik tile and even Mediterranean snow that traversed the vast network of the Mediterranean sea, the navigation of the shared Mediterranean sky also witnessed diverse trades of celestial globes, quadrants, armillary spheres, incense burners, and planispheric astrolabes that transformed the vision of human existence in the universe. More than any other scientific figures of the 16th century, astronomers operated within cross-cultural networks and were highly knowledgeable of adjacent cultures.
The astronomer’s astrolabe (a Ptolemaic instrument reconfigured and perfected in the medieval Islamic East) was unique in that its utility transcended boundaries between function and ornament. Through the process of holding the astrolabe aplomb and measuring the angle between the viewer and a specific star in the sky using, one could turn the dials and recreate a miniature model of the night sky. Alternatively, the astrolabe prefigured the meridian line in that it functioned as a portable sundial; regardless of day or night, one could hold heaven in hand. The design of the rete of the astrolabe superimposes a regulated grid of the instrument maker’s choice over the stereographic projection of the night sky. This act of imposing symmetry over the asymmetrical layer of the starry sky would be of great interest to artists and architecture of High Renaissance, wherein painting and building acted as metaphysical sutures between the divine and human realms. By capturing and recreating the dimensions of the cosmos, heavenly attributes of prudence, temperance, and mediation were evoked through art in response to a world of expansion, shifting scientific notions of the universe, and political unpredictability.
The Eastern tradition of oral intellectual dissemination has left scarce physical evidence for historians of Islamic art to directly point and signify meaning and path of influence. Similarly in Italy, the climate of the Counter-Reformation and condemnation of Galileo and Copernican alliances has left a void of explicit signification in astronomical and cosmological knowledge. Complicating accessibility further, the Pythagorean Neo-Platonism that underlie both Islamic and Italian Golden Age cosmologies require knowledge of numerical and mathematical symbolism to decode languages of secrecy and enigma. With these conditions in mind, it is through the tracing of the appearance of the astrolabe and its legacy within the humanist culture that I seek to connect with advancements in visual culture that led to shifts in early modern identities, thus illuminating the veiled cosmological dialogue between East and West.
Figure 3. Aristotle teaching astronomy while using an astrolabe on an Arabic Manuscript (Source)
“The Islamic redactions of the Almagest not only reformulated and paraphrased its contents but also corrected, completed, criticized, and brought the contents up to date both theoretically and practically.” – George Saliba
With the dissolution of Byzantium and emerging nodes of porous exchange with the Ottoman East, Northern and Central Italy gained access to coveted sources of ancient knowledge. Eastern Mediterranean scholars such as Basilios Bessarion, Guillaume Postel, Ciriaco d’Ancona, Nicholas of Cusa, Marsilio Ficino, and George of Trebizond (to name only a few), brought with them fluency of Hippocrates, Pythagoras, Plato, Plotinus, Euclid, and most importantly, Ptolemy’s Almagest. This 2nd-century mathematical and astronomical treatise on the motions of the stars and planets was the critical source of ancient knowledge for astronomers in the East and West from the Middle Ages up until the Scientific Revolution. The Almagest was first translated in the Near East, with at least five iterations by the late 8th and 9th centuries. The translations gave rise to commentaries and subsequent commentaries of commentaries, locating the first sentiments of Ptolemaic scepticism in the Islamic world.
The first challenge to Ptolemy was put forth by a Muslim astronomer and mathematician from Seville active in 12th century Islamic Iberia, Abū Muḥammad Jābir ibn Aflaḥ. His work Iṣlāḥ al-Majisṭi (Correction of the Almagest) introduced spherical trigonometry as a way of correcting the mathematical inadequacies of Ptolemy. The commentary most circulated in Western Europe was that of the mid-13th-century work of Nasir al-Din al-Tusi. In need of a setting that would allow him to directly observe and correct the planetary tables for himself, the Maragheh Observatory was established in 1259 on the hills of Northwestern Persia.
At the observatory, Al Tusi produced the most accurate tables of planetary movement of his day, with his Zīj-i Īlkhāni (“Ilkhan Stars”) calculating the positions of the planets and the names of the stars. For his planetary models, he invented a geometrical technique called the Tusi-couple, an advancement that completely altered the configuration of the universe and consequentially of the astrolabe. Updating Ptolemy’s fundamental geometry that was first used to construct the astrolabe, Al-Tusi applied the concentric circle to the layout of the instrument’s tablets. The Maragha Revolution was thus characterized by a shift away from the philosophical foundations of Aristotelian cosmology and Ptolemaic astronomy in favor of individual empirical observation and mathematical application of astronomy and nature as a whole, considered by Saliba as “a Scientific Revolution before the Renaissance.” This method was promulgated by prominent figures of the Maraghah and Samarqand Observatories, such as Ibn al-Shatir, Ali Qushji, al-Biruni, and al-Khafri.
In addition to the practice of astronomical innovation and production of instruments, it is also important to consider the theories that guided them. Alkindi, (abu-Yusuf Ya’kub ibn Ishak ibn Sabbah al-Kindi), who led the 8th century House of Wisdom in Baghdad, worked to promote the Arab assimilation of Indian, Greek, and Persian science. His treatise, On the Stellar Rays, prefigures the notion that astrology, physics, and psychology should be interlaced. Alkindi wrote of the presence of “rays” in earthly objects that correspond to rays of the stars and planets, thus concluding that heaven and earth exist in reciprocal relation to one another. Even further, Alkindi supported the idea of human agency against the divine- attributing to the arts inherent occult capabilities that could be exercised without any involvement of a higher power and by the individual alone. In Gulru Necipoglu’s “The Topkapı Scroll: Geometry and Ornament in Islamic Architecture”, her unfolding of the intricate Timurid geometric illustrations gives access to an understanding of geometry in the service of Islam that involves an inner spiritual knowledge in connection with the divine. She describes a group of Mesopotamians from Harran as, “a sect of star worshippers who had synthesized the late antique Neo-Platonic heritage of the Alexandrian school with Pythagorean-Hermetic elements and Babylonian astrology.” Renowned for their skill as astrolabe makers, this connection of theory and praxis, of mystical and functional is built into the materiality of the astrolabe. As carriers of mathematical formulas inscribed into their multiple tablets they were also heavily ornamented with Islamic scripture- and in the case of the Italian Renaissance, inscriptions of patronage and even encoded enigma.
“The three objects- the 1062 astrolabe, the 1462 astrolabe, and Piero’s painting- have been waiting hundreds of years to speak to us. The eight images of people alone call to mind a palette of human situations: ineffective leadership, indifference; aggression; treachery; self-sacrifice; salvation; hope, brutality, scholarship, bereavement, refugee status, hope for the youth of the future, memories of lost youth, benevolence. One could argue that Piero’s Flagellation of Christ is a painting about life.” -David King 
Jabir ibn Aflah’s Correction of the Almagest was translated from Arabic into Latin in 1175 by Gerard of Cremona, who was born in Northern Italy but moved to Toledo to study and translate ancient philosophies of science. It was not until the 16th century that Gerolamo Cardano would point out that the application of spherical geometry used by Regiomontanus in his 1463 On Triangles was drawn without reference from Jabir ibn Aflah’s commentary. An astrolabe made by Regiomontanus for Cardinal Bessarion is still extant today, physical evidence of one of the earliest sites of astrolabe exchange to circulate from East to West.
While visiting the court of Frederick III in 1460, Cardinal Johannes Bessarion came into contact with Georg von Peuerbach and his student Regiomontanus. Seeking assistance in a crusade to reclaim Constantinople and its history from the Turks, Bessarion proposed that Peuerbach and Regiomontanus create a new translation of Ptolemy’s Almagest from the original Greek while studying from his own home in Rome. Bessarion’s extensive connections all around Greece, Constantinople and Italy along with his deep commitment to intellectual advancement led to the development of his personal library as an informal academy for the translation of Greek manuscripts into Latin. Accepting the task, Peuerbach and Regiomontanus joined Bessarion’s household in Rome and spent the next four years looking for and copying mathematical and astronomical manuscripts for corrections to the Ptolemy. With Peuerbach’s unexpected death in 1461, Regiomontanus had to continue the promised task alone.
Aside from Peuerbach and Reiomontanus’ dependency on Eastern astronomical texts, the presence of the astrolabe circulating around the visual representations of Bessarion further this claim of Eastern influence. Just one of many examples is Vittore Carpaccio’s 1502, St. Augustine In His Study. In Patricia Fortini Brown’s essay, “Carpaccio’s St. Augustine in His Study: A Portrait within a Portrait”, she argues that the presence of the astrolabe distinguishes this as a double portrait of both St. Augustine and Bessarion. Brown’s use of Ruskin’s commentary on the painting illustrates the aura of mystical mathematics that resonated around the image of the astrolabe, “an ideal representation of the perfect mastery of the mind, in the fulfilment of the right desires of the Spirit.” The opened portal doors of Bessarion’s study reveal a collection of planispheric astrolabes which would have been a definite fixture in the workshop of Regiomontanus, who gifted an astrolabe that he made himself to Bessarion in 1462.
David King analyses the extant 1462 astrolabe constructed by Regiomontanus to a1062 also extant Byzantium astrolabe that Bessarion had brought back with him from Constantinople, (the back of the 1062 instrument entails a Greek inscription describing the astrolabe as an “icon of the universe”). No one having heeded Bessarion’s warning against the expansion of the Ottoman Empire, he witnessed and bore the weight of the fall of Byzantium in 1453 and Trebizond in 1461 to Sultan Mehmet II, “The Conquerer.” The elegiac couplet in the four lines on the back of Regiomontanus’ astrolabe contains an epigram that unlocks the hidden geometries, perspectives, and identities of Piero Della Francesca’s Flagellation of Christ– according to which the turbaned figure facing Christ is that of Mehmet II. King interprets the painting where Constantinople, Jerusalem, and Rome become one as achieving four goals: to memorialize the betrayal of Christ, to recall the suffering of the Eastern Church and Byzantium, to serve as consolation for three young men that had been close to Bessarion who had died, and to celebrate the arrival and activity of Regiomontanus in the service of Bessarion. It is my own opinion that the statuette of the classical god is that of Apollo- his golden hue and raising of the spherical sun as an artistic alliance to the heliocentric notions of the universe that Regiomontanus defended against the inaccuracies of his and Bessarion’s rival, Georg of Trebizond.
In Italy, we see the object of the astrolabe transformed into a vehicle for memory and commemoration. While King’s hypothesis requires a detailed reading for a full understanding of its intricacies, significant to my research here is the construction of a Renaissance astrolabe in conversation with an Eastern precedent, the use of the instrument to transmit semiotic knowledge, and the translation of this astrolabic message into the painted frame.
Shortly after the completion of the painting, Regiomontanus was appointed by Pope Sixtus IV to advise on the correction of the calendar using techniques established in his updating of Ptolemy and the astrolabe. Eerily, he died unexpectedly and without a known cause in Rome before publishing his final commentary on Ptolemy’s Almagest. Rumours of poisoned vengeance by the embittered family of Georg of Trebizond shadowed his death. Regiomontanus’ work was finally published in 1538, just as the work of Copernicus, who calls on different Islamic sources, would render Regiomontanus’ work obsolete.
Figure 4. “Using an Astrolabe” by Emily Winterburn (Source)
In the 1490s Copernicus was enrolled at the University of Krakow where he was taught by Professor Albert Brudzewski- a scholar of Aristotelian philosophy who taught astronomy to select students in private. Under this influence, Copernicus was first exposed to Brudzewski’s commentary on Georg Peuerbach’s Theoricae Novae Planetarum. While we have seen that Peuerbach’s own treatise was also influenced by shadows of Arab astronomy, a curious drawing serves as evidence that Copernicus was handling and studying the Arab Ptolemaic commentaries as primary sources himself.
The trigonometry that Copernicus outlined in the first part of his iconic De Revolutionibus was also rooted, without reference, in the work of ibn-Aflah. In the 1950s, ES Kennedy also proposed that the solar, lunar, and planetary models proposed by Ibn al-Shatir were mathematically identical to those of Copernicus 150 years later. The visual evidence leading up to this discovery relies heavily on the visual culture of the astrolabe and its mathematical drawings inscribed on the tablets. In 1973, evidence supporting Kennedy’s conjecture was put forth by William Hartner’s discovery of Copernican models that correlated to the Arabic diagrammatic inscriptions of al-Tusi.
But how would Copernicus come into contact with the work of Al-Tusi and Ibn Al-Shatir? Especially if he was not fluent in Arabic? With his formative years spent in Italy and inspired by the work of Peuerbach and Regiomontanus, he conducted a public observation of the brightest star of the Taurus constellation by the moon in 1497 Bologna. His years spent in Padua, the jubilee year of 1500 spent in Rome, and his many returns in and out of Italy would have exposed him to many traveling Arabist scholars, one of which was Guillaume Postel.
Charged with the task of buying Greek books during his 1536 delegation visit to the Ottoman Empire to negotiate a treaty with Suleiman the Magnificent, Postel instead bought at least 5 Arabic scientific texts, including several original manuscripts by Al-Tusi, as well as several astrolabes. Another Arabist of the time, Andreas Alpagus, lived and studied in Damascus, the same city Maragha astronomer Ibn-al-Shatir had been 100 years earlier. Alpagus, like Postel, was well versed in Arabic and brought his mathematical and scientific discoveries home with him to Padua at the turn of the 16th century. With Copernicus being born in Poland, so close to the borders of the Ottoman Empire, and his education in Northern Italy, it is believed that Copernicus came into contact with many of these traveling Arabist scholars, who would have translated texts and theories for him. This movement of valuable astronomic texts Westward would have explained why in this drawing, Copernicus copies and uses Arabic alphabetical systems to diagram his own work.
“While filtering the deleterious aspects of the heavens and one’s own character, the architecture of the Gubbio studiolo embodied a garden of earthly experience and a mechanism for divine contemplation. Whether metaphorically lifted by the machina of aedificatio or elevated by the virtues and colors of architectural ornament, contemplation was characterized as an ascent from the earthly body and was accounted for in physiological terms.” –Robert Kirkbride 
An earlier site of exchange that would place the influence of the astrolabe in Central Italy even before the arrival of Peuerbach, Regiomontanus, and Copernicus was the Sienese School of Mariano di Jacopo detto il Taccola and his student Francesco di Giorgio Martini. While the astrolabe of Regiomontanus traces the influence of the astrolabe into the realm of painting, Siena would provide proof that the astrolabe also had influences on contemporary architecture. Between 1424 and 1434, Taccola held a high position in this Camerarius of the Domus Sapientiae, or “House of Learning”. The Siena School hosted imminent figures of their time, including Mariano Sozzini, Leon Battista Alberti (who actually spent an entire month there in 1443), Filippo Brunelleschi and the polymath astrologer-cosmographer, Paolo dal Pozzo Toscanelli.
Through Taccola’s detailed illustrations in his 1430 De Ingeneis showing the use of the astrolabe for surveying purposes, the instrument is used here as a status symbol to market their proficiency in innovative building practice to the Holy Roman Emperor Sigismund. While it is uncertain why Taccola wrote the second treatise De Machinis, it is known to have been involved in a significant exchange between East and West. By 1450 a copy of the illustrated text ended up in the library of Sultan Mohammad II in Istanbul, who was fond of richly illustrated manuscripts depicting Western military architecture and engineering. It is believed that Ancona traded Taccola’s De Machinis to the library of the Sultan in exchange for Islamic instruments, which accounts for the knowledge and circulation of the astrolabe and its design in Siena.
Tacocola and Francesco di Giorgio’s richly illustrated codecettos with emphasis on measuring devices mark a significant rise of machine illustration, graphic prevalence over textual description, and instruments being embedded into architectural ornament- accounting for more accessibility of early modern technology such as the astrolabe. Aside from the functional use of the astrolabe in surveying and measuring, di Giorgio’s subsequent architectural work implores whether or not the astrolabe and its connection to the divine had an influence on his work at both the Studiolo of Gubbio and Urbino and in his Church Santa Maria delle Grazie al Calcinaio.
In 1475, di Giorgio continued the Sienese tradition of gifting ornamented treatises in his dedication of Opusculum de Architectura to Duke Federico III of Montefeltro. With a deep Vitruvian influence, this dedication won him the commission of the 1480 Gubbio and Urbino Studioli in the Palazzo Ducale. The walls of the Studioli are executed in wood-inlay intarsia, showing latticed cabinets that display objects reflecting Duke Federigo’s wide-ranging artistic and scientific interests, including one cabinet including an astrolabe and armillary sphere.
Robert Kirkbride traces the directed path of the gaze in the studiolo, sighting the presence of 11 hooks which contain objects of the most significance to Federico: a dagger, a scopetta, Federico’s armor (occupying five hooks), an astrolabe, an armillary sphere, a tablet, and a birdcage. Carved in detail, the astrolabe in this context has served both as a symbol to scholarship, but also as a mnemonic device of rhetoric invention. Kirkbride elaborates,
“Other figures hover enigmatically between the symbolic and utilitarian. The astrolabe and chess pieces, for example, offered rebuses for memory training and metaphors of prudent governance in addition to their more familiar applications in astronomical observation and gentlemanly gamesmanship.”
Kirkbride makes a larger claim about the phenomenological experience of di Giorgio’s design for the Studioli, drawing on the text of Marsilio Ficino and Nicholas Cusanus.
In exploring the cosmological implications of the room of intarsia, Kirkbride ties the inscription encircling the wall of the room to a literary reference by contemporary humanist Marsilio Ficino. The inscription begins with the word “ASPICIS”, which can be translated literally as “see how”, or adspicere “to look at”. Kirkbride points out that this word could double as a reference to astronomy, with the word of “aspect” also referring to “the relative positions of the heavenly bodies as they appear to an observer on the Earth’s surface at a given time”, or “the way in which the planets, from their relative positions, look upon each other”. This interlacing of geometry, optics, and divinity is further enhanced by di Giorgio’s gold, green, blue, red, purple, and gray ceiling- Ficino’s recommendation for colors that evoke the generative and protective influences of the heavens. Ficino’s Euclidian comparison of celestial bodies to “eyes” that channel spirituality through rays of light is reminiscent of the cosmology of Alkindi.
The presence of the astrolabe in a room designed to reverberate with the heavens is testament to the contemporary aesthetic of proportion and harmony. On the hills of Cortona, di Giorgio designed the architectural embodiment of divine geometries. In the 1480 Santa Maria delle Grazie al Calcinaio, di Giorgio’s elimination of side aisles in favor of thick supporting exterior walls allowed interior simplicity while still producing the effect of exterior monumentality. With three-nave bays leading to a central square, the geometry of the church forms a cube topped by an eight-sectioned dome. In Christiane Joost-Gaugier’s Pythagoras and Renaissance Europe: Finding Heaven, she points out to the Vitruvian perfection of the church culminating in the paired pilasters totalling in a number of 16 vertical columns, the perfect number for a Vitruvian temple. Only from the skies is it possible to see Di Giorgio’s efforts to distribute the eight windows of the dome’s lantern and drum in perfect proportion to the four arms of the church.
“The perfect animate being is one possessing sense and intellect. This being should be thought of as a cosmographer who has a city with five gates, which are the five senses. Through these gates messengers enter from all over the world, announcing the disposition of the entire world … The cosmographer should sit and note down all things that are related to him, in order to have a description of the entire perceptible world represented in his own city. … The cosmographer therefore tries as hard as he can to keep all the gates open, to listen constantly for the reports of new messengers, and to bring his description ever closer to the truth. Finally, when he has made a complete representation of the perceptible world in his own city, he compiles it into a well-ordered and proportionately measured map lest it be lost.” – Nicholas of Cusa
In what would be the Florentine equivalent of the Siena School was the humanist circle of Nicholas of Cusa, Toscanelli, and Filippo Brunelleschi. Toscanelli was the recipient of two treatise dedications from Nicholas of Cusa in 1445, evidence of a strong friendship that had been forged in their studies together in Padua. Trained in Greek, Latin, Hebrew and Arabic, Cusa’s trip to Constantinople with the task of reconciling Eastern and Western Churches may have been unsuccessful, but he returned with sixteen books on astronomy, a wooden celestial globe, a copper celestial globe, an astrolabe, and the inspiration or his pivotal 1440 piece, De Docta Ignorantia. These instruments and manuscripts established his theories of heliocentricism, the possible existence of infinity, and the assertion that man’s knowledge of the universe was incomplete.
The reciprocity of influence between Cusa and Toscanelli was undeniable, particularly in Toscanelli’s own cosmographical pursuits in his Spice Island map for Columbus as the first to express the possibility of a passage to India cartographically. Toscanelli’s 1474 letter to his friend Fernan Martinez de Roriz, a Portuguese canon who later became King Alfonso’s confessor at the Court in Lisbon, details the route according to Toscanelli’s oceanic measurements. While the original map was lost, reconstructions by Heinricus Martellus and the Erdapfel of Martin Behaim of the map are the only two extant non-Ptolemaic world maps of the 15th century to be graduated in latitude and longitude.
Toscanelli’s experimental and innovative application of scientific knowledge was passed down to a friend, collaborator, advisee, and student Filippo Brunelleschi. Toscanelli’s piercing of Brunelleschi’s dome and laying out of the meridian in the Florentine cathedral in 1475 have sensuous similarities to the experience of sunlight filtering through the astrolabe’s pierced sighting holes signalling the Islamic prayer time, (the shared materiality of bronze is also interesting). In the Islamic world, astrolabes functioned as a source of portable sacrality for traveling Muslims who needed to determine prayer times and their direction to Mecca independently. By setting the alidade at a shadow length appropriate for a given prayer, the astrolabe was hung plumb, and the prayer was begun when a ray of sunlight passed through pinholes of the alidade’s sighting plates. With Toscanelli’s meridian, at midday on the Summer solstice, a beam of sunlight, passing through a hole in a small bronze shelf inserted in the wall at the base of the southern window in the lantern-lit up an inlaid marble disk in the floor of the cathedral. With no written treatise for the purpose of the Meridiana, it is only through Toscanelli’s correspondence with Regiomontanus that we know the project to be motivated by a desire to check whether the inclination of the earth’s axis changes over time.
Toscanelli’s projection of the astrolabe into cosmologic and cosmographic design, as well as his connections with Gemistus Platho, Nicholas Cusanus, Ficino, and Pico della Mirandola align him with a design ethos modelled after Pythagorean ideologies. That Pythagorean ideologies involve the technologies of the astrolabe are inherent, in that any instrument dedicated to mensuration of the earth and sky support the cause of building geometric divinity. Pythagorean influence has visual evidence in the work of his student Brunelleschi’s Pazzi Chapel, the Sacristy of San Lorenzo, San Lorenzo, Santo Spirito, and Santa Maria degli Angeli. The Pythagorean notion of spherical domes of the heavens regulating the cube of the earth below is accentuated by the references to celestial divinity in the proportioning of the vaults. Just as Toscanelli had experimented in translating the astrolabe’s measurement of time through the observation of the eclipse into architecture, so too did Brunelleschi’s domes translate the measurement of time in the night sky.
Two cerulean frescoes detailing a specific moment in the sky over the northern hemisphere occupies the entire surface of the cupola above the Scarsella of San Lorenzo as well as the Pazzi Chapel. While no written account of the frescos exists, the conjecture is that they may have been painted by Giuliano d’Arrigo, known as Pesello, undoubtedly under the supervision of an astronomer, who would have been Toscanelli. The scientific import of the representation is revealed by the extreme precision with which the celestial bodies are positioned. Appearing in gold against the blue background of the sky are the Moon, the Sun, Jupiter, Venus, Mercury and the main coordinates of the celestial sphere, while the personifications of some of the constellations are outlined in black with white highlights. The position of the planets shows that the painting represents the sky over Florence on July 4, 1442, evidently a date-worthy of being recorded, and perhaps connected to the arrival of René of Anjou. This hypothesis is supported by the fact that an almost identical fresco was painted a little later in the Pazzi Chapel, a family with close ties to the Angevin sovereign. One can almost imagine Toscanelli, Brunelleschi, and Pesello setting an astrolabe to correspond with the date of July 4, sketching out the positions of the stars and houses of the zodiac, and collaborating on how best to translate that celestial moment into architectural space.
Di Giorgio’s involvement in the 1475 war between Siena and Florence put him into close contact with Giuliano da Sangallo, between whom information on the astrolabe may have been exchanged. This exchange is made all the more probable upon examination of a curious drawing by the hand of Antionio da Sangallo the Younger.
Living now in the Uffizi Gallery is Antonio da Sangallo’s meticulous recreation of a ninth-century astrolabe from Baghdad. So detailed is Sangallo’s drawing of both the front and back of the astrolabe, that we are able to clearly decipher the astrolabe maker as Khafif, the apprentice of Ali bin Isa. Sangallo’s careful rendering of the instrument is in isolated parts- the alidade, the pin, and the rete. George Saliba, a scholar who has worked extensively on scientific exchange in the Mediterranean, brings up the point that Antonio Sangallo was at the time working on the building of St. Peter’s in Rome. The 10th-century text by astronomer Abd al-Rahman al-Sufi cites an astrolabe such as this as being capable of solving 380 mathematical and astronomical problems. Accordingly, Saliba attributes Sangallo’s interest in the astrolabe to the functionality it would provide to such an engineer. Supported by the extreme detail to which Sangallo takes apart this astrolabe, Saliba goes further to illustrate the extent to which Renaissance men of science were dependent not only on the technology of the world of Islam, but a dependence on the accompanying theoretical scientific results also produced in the world of Islam.
Exploring the role of the architect caught between this exchange of scientific and cosmological theories of East and West, the design aesthetic of Sangallo architecture is one in constant dialogue with the mutual measurements of heaven. Antonio da Sangallo the Elder’s Montepulciano 1508 church of San Biagio, “shows the purity obtainable from the unifying powers of geometry and number.” With a close to perfect geometry in the dome’s articulation of 16 pilasters both inside and out, the diameter of the firmament of Sangallo’s dome is exactly equal to that of the centralized cube below. Joost-Gaugier again urges the viewer to consider the view from above, in which one can view an architectural response to Nicholas of Cusa’s manifesto for the pursuit of a more complete universal knowledge.
Antonio’s proclivity for architectonic harmony is also seen in San Biagio’s precedent of his brother Giulio da Sangallo’s 1485 unfinished Church of Santa Maria delle Carceri at Prato. Natural light floods the centralized space of the interior from the 12 windows of the dome and 6 windows of the lantern- both cosmological numbers associated with the heavens. Situated as a detached and visible from all four sides, this church stands as the first example of a perfectly balanced Greek cross plan with a mimetic quality of interior and exterior unity. In the same way that the astrolabe uses light to signal the commencement of sacred salat, Giulio da Sangallo crafts the placement of the building to achieve a similar effect to use light as a source of veneration for the image of the Virgin. As the historic site of miraculous apparitions, Giulio oriented the building so that exactly on the day of the miracle, and just at the hour in which the chronicles report the occurrence of the first apparition – at 3:18 p.m. on July 15– an ellipse of light glistens at the center of the white marble altar, remains there a few minutes, and then disappears toward the lower right. Similarly, on the day of the summer solstice when the azimuth of the Sun coincides with the main axis of the church, a beam of light falls from the windows in the lantern, perfectly centring the fresco of the Virgin.
“Undoubtedly the long physical indisposition I have suffered for so many years would have put me under the ground if my mind, continually sweetened by the contemplation of astronomy, had not attenuated the weakness of my body.” -Pier Vincenzo Rinaldi
The miraculous manipulations of light-mediated through architectural space by those acquainted and versed in the technology of the astrolabe is practiced in another site of exchange- this time in the Perugian family of Rinaldi-Danti.
Egnazio Danti was exposed to the practice of painting and building by his father Giulio Danti, who studied architecture under Antonio da Sangallo. His interests in astronomy can be traced to the influence of his grandfather Pier Vincenzo Rinaldi, who during the outbreak of the Perugian plague in the 1490s attributed his survival to the devoted observation of the stars as recorded in his own writing above. While not much is known of the Danti family, this excerpt survives from a preface that Rinaldi wrote to his own translation of Sacrobosco’s Sphere. While Johannes de Sacrobosco is an interesting point of scientific exchange himself, all that should be noted for our path is that his De sphaera was a 13th-century introduction to astronomy that merged Ptolemy’s Almagest with the aforementioned Islamic commentaries.
Having just pledged to Dominican monastic life, Egnazio received the call to cosmography from Cosimo De Medici in 1563. In need of a man who possessed the combined skills of cosmographer, designer, and painter, Cosimo embarked on the creation of the Stanza del Guardaroba in the Palazzo Vecchio. The Guardaroba boasts 57 floor to ceiling maps of various regimes drawn as cartographically accurate as possible. Roused at the accuracy and speed with which Danti was producing the maps, Cosimo moved the friar-cosmographer from Santa Maria Novella into the palace walls and began a collaborative vision to reform the papal calendar.
Judging from the relative accuracy of the maps given limited resources as well as allusions to the circular brass form and the crowning throne of the astrolabe, we see Danti’s familiarity with the instrument as early as 1563. This proficiency with astronomical instruments would factor into the project of calendar reform, when in 1572-74 Danti mounted two objects of astrolabe ancestry onto the facade of Santa Maria Novella: an armillary sphere and a quadrant that are still in part there today. Whether these instruments were mounted as an advertisement for Cosimo’s calendar reform or in order to obtain quantitative data is complicated by the fact that Danti also began work on the construction of a meridian line in the church’s interior. The choice of the cathedral had less to do with Danti’s Dominican affiliation and more to do with the agreeable conditions for the observation that churches provided, and in his own words, “it was the most convenient and stable in Florence, being strong enough to stand immobile as long as the world lasts, and being freely exposed to the south so as to receive the rays of the sun at the times of the equinoxes from morning until evening.” Danti’s publication of his grandfather’s translation of Sacrobosco revealed the source of his astrolabic intelligence.
Danti would continue the family tradition of passing down the knowledge of the astrolabe and its workings after the unveiling of his armillary sphere attracted a crowd and new patron to witness the play of light as the sun was captured exactly between Danti’s golden rings. Danti was then patronized by Cosimo’s brother Ferdinando I, and just as Regiomontanus had given to Bessarion, and Danti’s grandfather had given to Alfano Alfani, so to did Danti present to his new patron what was said to be the most beautiful and exquisitely fashioned astrolabe in all of Italy. Having earlier given Cosimo a Mercator astrolabe and seeing his patron’s admiration but total incomprehensibility as to how the instrument functioned, Danti also presented Ferdinando with a dedicated treatise on the astrolabe which detailed how it worked. The first edition of Trattato dell’ Uso, e della fabbrica dell’ astrolabio was published by Danti in 1569. It was the first book to be published in Italy on the astrolabe.
With instruments mounted and the laying of the marble meridian, everything was in place for the Medici to begin an impressive campaign in astronomical advancement. However, Cosimo’s untimely death in 1574, and the succession of his cosmologically averse son Francesco to power left the Meridiana incomplete and Danti conveniently dismissed from Florence to Bologna. Danti’s continued pursuit of the sun without a specific patron raises the question of his true motivations; Was it purely perfecting the date of Easter? The late Gothic creamy interiors of Bolgona’s San Petronio provided the perfect setting for Danti’s marble engraving of the houses of the zodiac for the sun to dance upon. Danti’s projection of the portable workings of the astrolabe onto the scale of the monumental San Petronio impressed Pope Gregory XIII to such greatness that in 1581, Danti would receive his final call for cosmography at the Vatican.
In what is perhaps his most impressive work, Danti completed the Italian maps adorning the walls of the Belvedere Gallery. Within the context of circulating new cosmologies, especially those associated with the Reformation, the church used cosmography as a way to assert the universality of the church. Danti had also constructed the Torre dei Venti on the roof of the Vatican, which functioned in architectural scale as an anemoscope, an instrument he had invented to measure wind. Here in this tower of winds, Danti constructed another meridian lines according to the principles laid by his treatise of the astrolabe. So pleased was Gregory with Danti’s work that he awarded him the highest honor of an Alatrian bishopric. Danti’s work is testament that with the right alliances, under the right campaigns and with a vast amount of knowledge, one could practice advanced astronomy with subtle Copernican sympathies with the funding of the Vatican itself.
This focus of Westward movement is not to say that Italian architecture and science exchanged only with spectres of medieval Islamic astronomers past, to stop here would be detrimental to a rounded study of cosmological exchange in the early modern Mediterranean. Islamic astronomy was not only active well into the 16th century, but also engaging with developments occurring in the West. For this, we have the Istanbul observatory of Takiyuddin and the architect Mimar Sinan.
An unexpected direction of influence that may in fact be a direct result of both a heritage in advanced astronomy and also an eye kept on Italy is the interaction between Mimar Sinan and Takiyuddin. As we have seen in the case of Piero della Francesco, Francesco di Giorgio, Brunelleschi, the Sangallo family, and patrons such as the Medici and the Vatican, there was a marked influence directly from astronomers such as Regiomontanus, Toscanelli, Cusa and Egnazio Danti. In the case of the Galata Observatory, an illustration of the scientific instruments and library of Takiyuddin reflect influence directly from the architect. Beginning at the bottom right corner of the 1581 Shahanshanama watercolor, the gaze is directed from ecliptic measures and celestial spheres, up to triangular rulers and quadrants pointed towards the sources of their research: the library of scientific manuscripts. Just below the collection of manuscripts is Takiyuddin explains the workings of the astrolabe to his colleagues. Necipoglu details the development of the neighborhood surrounding Sinan’s residence into an intellectual center of great scholarship. She affirms this from a 1578 incontestable imperial decree ordering that the mathematical treatises kept in the muezzin of Mimar Sinan Mahallesi be transported to Takiyuddin’s observatory. The esteemed collection of manuscripts, once belonging to the scholar Molla Lutfi, serves as evidence to Sinan’s own incorporation of these scientific theorems and the use of the astrolabe into his own building practice, particularly in his surveying for the Kirkcesme water project.
In the only known portrait of Sinan, the Ottoman use of a scientific instrument echoes the Italian employment of the astrolabe in visual culture as a status symbol for intellectual prowess. Necipoglu illustrates this point in her analysis of the watercolor of Sinan managing the building of Sultan Suleyman’s mausoleum. By depicting him holding a cubit measure, this symbol of intellectuality attests to his rigorous training in geometry and sets him into the realm of the divine. “The exalted self image projected in Sinan’s autobiographies echoes the Lives of Italian artists and architects, with their notion of the artwork as a material trace of it’s makers mental powers of invention. The term ‘divine’ (divino), used for Brunelleschi and Michelangelo, is also applied to Sinan by his biographer, who is intent on advertising the chief-architect’s God-given genius: ‘divine maestro’ (aziz-i kardan), ‘divine architect’ (mimar mubarek).”
While the example of Sinan’s Suleymaniye Mosque alludes to a shared Italian-Islamic aesthetic of the domed cube module we have seen in the raw geometries at Cortona and Montepulciano, the Selimiye mosque signals a shift in Ottoman expression of the divine:
“While his Italian contemporaries focused much of their creative energy on the classical orders and on pedimented facades with classicizing sculptural details, Sinan adopted an elastic approach to architectural design.. His steadfast devotion to the geometry of hemispherical domes also brought him closer to the Roman tradition than Renaissance architects, who were equally attracted to domes with elevated profiles like that of the Florence Cathedral.”
In an architectural expression of the shifting cosmologies being exchanged throughout the East and West, Sinan’s Edirne mosque reflects the hybrid image of progressive and deeply historic identity of the Early Modern Mediterranean world:
“Intended as an unmatched exemplar ‘worthy of being seen by the people of the world’, the multivalent Selimiye transcended the limits of Ottoman architectural tradition. By boldly reclaiming the Romano-Byzantine and Islamic roots of that tradition, and perhaps even making an indirect reference to contemporary Italian Renaissance architecture, the elderly chief architect in his eighties created a timeless testament to his creative genius.”
In the dome of the Selimiye, the cosmic inscriptions echo the shape of Islamic astrolabic thrones, again translating into architectural scale the space of divine inscription. Within the radiance of Selimiye however, there lingered a sense of irresolute panegyric. As Necipoglu points out, the timing of Selim II’s death and Murad III’s disinterest in the building prefigured what Sai details in his “Complaint about the times” as a decline in patronage of the intellectual arts. His line, “nobody pays attention anymore to whose inner world is rich”, can be seen as a shift from the deep roots of science and art based upon “inner knowledge”. Necipoglu suggests that while this may have been in regards to Sai’s own field of poetry, it could be applicable to Sinan’s own sentiments on diminished royal patronage. This shift in the value of imperial support for arts and science can also be seen in Takiyuddin’s Galata Observatory, marking perhaps a larger change in the Ottoman Empire.
In 1574, the Ottoman court historian Mustafa Ali describes the “disorder of the age and perturbations of space and time which appeared, one by one, after Murad III’s accession, and which proved to be the cause of the disruption and degeneration of the world.” Notoriously superstitious and in need of a remedy to the prophecies of the breakdown of the Ottoman Empire, Murad III turned to Takiyuddin to return cosmic order to the Ottoman Empire. The comet of 1577 called into service not Takiyuddin’s mathematical talent, but that of his astrological diplomacy. The reading was lyrical enough, “Oh world swaying King, The candle of your pleasant society shall be resplendent”, but it wasn’t enough to elevate Murad out of his melancholy and left Taqi al Din and his astrological instruments with sentiments of bad omen. Murad, depressed at the state of his personal and military losses, ordered for the close of the observatory in 1580, only 3 years after it had been opened. This closing undermined Takiyuddin’s significant contributions of the construction of mechanical clocks, talismans, automata, and the significant updating to astronomical tables of the 16th century. The instruments produced at Galata were so advanced, it is said that even the observatory of Tycho Brahe on the Danish island of Hven imitated their instruments.
Fabrizio Bonoli has termed this historical moment, “the passing of the European torch from Arab astronomy to that of Europe, marking the conclusion of a vast process that had begun over five centuries earlier: the confluence in Europe of Arab-Islamic culture with the Greek culture of the Classic and Hellenistic ages mediated and developed by Near Eastern scholars.”
It is not my intention to claim that because of a heritage in advanced astronomic theory, Ottoman architecture had an accompanying architectural practice that heeded no influence from the West. The backwards glance of Renaissance astronomers and architects should not undermine two significant contributions of 14-15th century Italy: one, astronomic advancements to questions raised but unresolved in early Islamic astronomy, and two, architectural reification of those astronomical advancements. In her manuscript “Age of Sinan”, Necipoglu outlines in detail the returned gaze of Ottoman to Italian architecture, particularly in the case of Sinan and Palladio and Ottoman travelers and Antonio da Sangallo the Younger’s wooden model of St. Peter’s in Rome.
By focusing this research on isolated exchanges of the astrolabe in the 15-16th century in Renaissance Italy and the Ottoman Empire, it has been my goal to bring to light a shared pursuit of a divine truth rooted in mensuration of the universe in both East and West. The path of the astrolabe from Ancient and Medieval East to Western Europe and back again to the Ottoman Empire traces the symbol of the astrolabe to uses of building and engineering function, an emblem of intellectual superiority, a rhetorical device for memory and commemoration, and most significantly, an instrument that allowed the architect to create and compete with designo of the divine.
The tradition established in Quattrocento and Cinquecento Italy of a collaborative and hybrid practice uniting roles of mathematicians, astronomers, astrologers, artists, architects, priests and patrons was to be carried out in the age of Galileo as well. Following the decline of royal patronage in the Ottoman Empire and the menacing environment surrounding the Council of Trent in Italy, the passed torch from Eastern to Western astronomy and from Copernicans to Galileans kept alive the artist-astronomer cult of secret science. The fact that the invention of the telescope didn’t render the continued laying of meridian lines attests to the enduring symbol of the astrolabe and its sacrality. Toscanelli’s meridian was perfected in 1755 by grand-ducal astronomer Leonardo Ximenes, and Danti’s meridian of San Petronio was perfected in 1695 by Giovanni Cassini. In the example of Emmanuel Maignan, the physicist-theologian who was called to Rome to teach mathematics at the Trinita dei Monti, the astrolabe merges with meridian and takes on an ornamental commemorative status. While in the convent, Maignan spent years hand-drawing exact positions of the constellations in what is now known as the “Astrolabe Catoprique”. His commission to draw a non-functional ceiling meridian at Palazzo Spada served to advertise Bernardino Spada’s cultivation of study and establish the intellectual presence of this as a meeting place for members of the Accademia dei Lincei.
In Eileen Reeves, “Painting the Heavens”, she explores how artists in their decoration of church murals were able to participate and insert themselves into the biggest scientific debate of their time. Illustrated most powerfully in Ludovico Cigoli’s Immacolata in the dome of the Pauline Chapel in Santa Maria Maggiore, Reeves argues that the rendering and positioning of the moon were strategic in order to elucidate astronomical and religious arguments, “To see the entire portrait of the Immacolata is to understand the particulars of Galileo’s argument- that the moon is rough, dark, and wholly impervious light- and the amplitude of Cigoli’s version, where the science cannot be severed from the scriptural.”
Through the use of astrolabe as an object of mediation and reconciliation between Eastern and Western metaphysics and scientific philosophies, architects of the early Renaissance paved the way for the High Renaissance based on the same values of art as an art of ideas. With the defining characteristic of the idealization of nature through the construction of visual order exemplified by geometric harmony, a mutual modernism blossomed in both the East and West and elevated the architect to the domical layer of divinity.
Ben-Zaken, A. 2010, Cross-cultural scientific exchanges in the eastern Mediterranean, 1560-1660, Johns Hopkins University Press, Baltimore.
Galluzzi, P. 1999, Renaissance engineers from Brunelleschi to Leonardo da Vinci, Giunti :Istituto e Museo di storia della scienza, Firenze.
Heilbron, J.L. 1999, The sun in the church: cathedrals as solar observatories, Harvard University Press, Cambridge, Mass.
Joost-Gaugier, C. 2009, Pythagoras and Renaissance Europe: finding heaven, Cambridge University Press, Cambridge; New York.
Katz, V.J. & Imhausen, A. 2007, The mathematics of Egypt, Mesopotamia, China, India, and Islam: a sourcebook, Princeton University Press, Princeton.
Kennedy, E.S.(., King, D.A. & Saliba, G. 1987, From deferent to equant: a volume of studies in the history of science in the ancient and medieval Near East in honor of E.S. Kennedy, New York Academy of Sciences, New York, N.Y.
Kennedy, E.S.(., Kunitzsch, P., Lorch, R.P. & Abū Jaʻfar Aḥmad ibn ʻAbd Allāh, active,9th century 1999, The melon-shaped astrolabe in Arabic astronomy, F. Steiner, Stuttgart.
King, D.A. 1993, Astronomy in the service of Islam, Variorum, Aldershot, Hampshire, Great Britain; Brookfield, Vt., USA.
King, D.A. & Holzschuh, B. 2007, Astrolabes and angels, epigrams and enigmas : from Regiomontanus’ acrostic for Cardinal Bessarion to Piero della Francesca’s Flagellation of Christ, Steiner, Stuttgart.
Kirkbride, R. 2008, Architecture and memory: the Renaissance studioli of Federico de Montefeltro, Columbia University Press, New York.
Nasr, S.H. 1968, Science and civilization in Islam, Harvard University Press, Cambridge, Mass.
Necipoglu, G., Al-Asad, M. & Paul Getty Center for the History of Art and the Humanities., J. 1995, The Topkapi scroll: geometry and ornament in Islamic architecture: Topkapi Palace Museum Library MS H. 1956, Getty Center for the History of Art and the Humanities, Santa Monica, CA.
Necipoglu, G., Arapi, A.N. & Günay, R. 2005, The Age of Sinan: architectural culture in the Ottoman Empire, Princeton University Press, Princeton.
North, J.D. 2008, Cosmos: an illustrated history of astronomy and cosmology, University of Chicago Press, Chicago.
Paschos, E.A.(. & Sotiroudis, P. 1998, The schemata of the stars: Byzantine astronomy from A.D. 1300, World Scientific, Singapore; River Edge, N.J.
Reeves, E.A. 1997, Painting the heavens: art and science in the age of Galileo, Princeton University Press, Princeton, N.J.
Saliba, G. 2007, Islamic science and the making of the European Renaissance, The MIT Press, Cambridge, Mass.
Samsó, J. 1994, Islamic astronomy and medieval Spain, Variorum, Aldershot, Hampshire, Great Britain; Brookfield, Vt., USA.
 Saliba, G. 2007, Islamic science and the making of the European Renaissance, The MIT Press, Cambridge, Massachusetts, 127.
 North, J.D. 2008, Cosmos: an illustrated history of astronomy and cosmology, University of Chicago Press, Chicago, 148.
 Katz, V.J. & Imhausen, A. 2007, The mathematics of Egypt, Mesopotamia, China, India, and Islam: a sourcebook, Princeton University Press, Princeton, 4.
 Saliba, G. 2007, Islamic science and the making of the European Renaissance, The MIT Press, Cambridge, Massachusetts, 28.
 Necipoglu, G., Al-Asad, M. & Paul Getty Center for the History of Art and the Humanities.,J. 1995, The Topkapi scroll: geometry and ornament in Islamic architecture: Topkapi Palace Museum Library MS H. 1956, Getty Center for the History of Art and the Humanities, Santa Monica, CA, 131.
 King, D.A. & Holzschuh, B. 2007, Astrolabes and angels, epigrams and enigmas: from Regiomontanus’ acrostic for Cardinal Bessarion to Piero della Francesca’s Flagellation of Christ, Steiner, Stuttgart, 188.
 Katz, V.J. & Imhausen, A. 2007, The mathematics of Egypt, Mesopotamia, China, India, and Islam: a sourcebook, Princeton University Press, Princeton, 4.
 King, D.A. & Holzschuh, B. 2007, Astrolabes and angels, epigrams and enigmas: from Regiomontanus’ acrostic for Cardinal Bessarion to Piero della Francesca’s Flagellation of Christ, Steiner, Stuttgart, 159.
 Kennedy, E.S.(., King, D.A. & Saliba, G. 1987, From deferent to equant: a volume of studies in the history of science in the ancient and medieval Near East in honor of E.S. Kennedy, New York Academy of Sciences, New York, N.Y., 260.
 Paschos, E.A.(. & Sotiroudis, P. 1998, The schemata of the stars: Byzantine astronomy from A.D. 1300, World Scientific, Singapore ;River Edge, N.J., 27.
 Kirkbride, R. 2008, Architecture and memory: the Renaissance studioli of Federico de Montefeltro, Columbia University Press, New York., 35.
 Galluzzi, P. 1999, Renaissance engineers from Brunelleschi to Leonardo da Vinci, Giunti: Istituto e Museo di storia della scienza, Firenze, 47.
 Kirkbride, R. 2008, Architecture and memory: the Renaissance studioli of Federico de Montefeltro, Columbia University Press, New York, 63.
 Heilbron, J.L. 1999, The sun in the church: cathedrals as solar observatories, Harvard University Press, Cambridge, Mass, 333.
 Saliba, G. 2007, Islamic science and the making of the European Renaissance, The MIT Press, Cambridge, Massachusetts, 67.
 Joost-Gaugier, C. 2009, Pythagoras and Renaissance Europe: finding heaven, Cambridge University Press, Cambridge ;New York, 112.
 The grandfather, Pier Vincenzo Rinaldi, was a poet amongst his many other intellectual pursuits. His friends nicknamed him Danti, as a reference to Dante, and the name stuck and eventually overrode the name Rinaldi.
 Heilbron, J.L. 1999, The sun in the church: cathedrals as solar observatories, Harvard University Press, Cambridge, Mass, 72.
 Heilbron, J.L. 1999, The sun in the church: cathedrals as solar observatories, Harvard University Press, Cambridge, Mass, 79.
 Necipoglu, G., Arapi, A.N. & Günay, R. 2005, The age of Sinan: architectural culture in the Ottoman Empire, Princeton University Press, Princeton, 141.
 Ibid., 135.
 Ibid., 103.
 Ibid, 256.
 Ben-Zaken, A. 2010, Cross-cultural scientific exchanges in the eastern Mediterranean, 1560-1660, Johns Hopkins University Press, Baltimore, 24.
 Ibid., 32.
 North, J.D. 2008, Cosmos: an illustrated history of astronomy and cosmology, University of Chicago Press, Chicago, 148.
 Reeves, E.A. 1997, Painting the heavens: art and science in the age of Galileo, Princeton University Press, Princeton, N.J., 175.
Original published date 28 May 2020