Designing a legible grid for lunar observation

Seventeenth-century selenographies can be associated with early modern paper instruments designed to fulfil a variety of didactic and heuristic functions addressing demonstrative, argumentative, mnemotechnic and observational needs.Footnote ⁸ These artefacts were valuable commodities in patronage cultures and the print economy, and in this sense they were also instruments of prestige. With methods known to early modern botany, anatomy and antiquarianism, producing a telescopic picture of the Moon relied on comparing and collating as many as possible piecemeal sketches of lunar phases made over time by different people in varied instrumental and observation conditions.Footnote ⁹ Selenographers (who also identified broadly as ‘astronomers’, ‘mathematicians’, ‘cosmographers’ and ‘natural philosophers’) appropriated different styles related to diagrammatic, cartographic and naturalistic pictorial modes. Pictorial rationale relied on a variety of factors, including authorial intention, artistic skill and patron–client relations.Footnote ¹⁰

Artfully contrived, a selenography was a technical device designed to help record the movement of celestial bodies against specific parts of the visible lunar disc.Footnote ¹¹ This tool enhanced methods for calculating planetary distances, terrestrial longitude and other astronomical questions through the ideals of accurate instrumentation and standardized collective observation. Selenographies were widely promoted by their makers as methods for the determination of longitude. More comprehensively, however, they were made to measure and represent changes of space over time, a basic preoccupation for early modern astronomy, as Thomás Haddad has argued in his excellent essay.Footnote ¹² The lunar graphic would serve as a template for the Moon's changing shape in the sky, against which the passing of a planet or the progression of an eclipse could be geometrically described and recorded. With the assistance of the telescope, the satellite's most prominent regions or maculae (a Latin term used technically in optics to refer to spots or blurs) could be used as enhanced referents for observation and notation. Maculae served, for instance, to note precisely at what time the Earth's shadow touched a certain region of the lunar disc during an eclipse. They could also help the observer trace imaginary lines between a star or planet and a precise spot on the edge of the Moon. Such observations informed the most technical issue that selenographers aspired to resolve: a full understanding of the satelliteʼs motion and, especially, of its libration.Footnote ¹³

Selenographies were syntheses of observations stabilized on paper graphics. They helped train and anchor the astronomer's eye. Specific spots were learned by heart so that at the telescope skilled observers would have a more or less detailed mental map for recording celestial phenomena. Just as geographical information was communicated without the need of an actual map, selenographic observations were conveyed through tables with hours, minutes and seconds that indicated temporal changes of light over discrete spots of the lunar disc. These tables allowed information to be shared, interpreted and contested effectively, to compete and to make claims.Footnote ¹⁴ Ideally, people in different parts of the world would share the same nomenclature to record, compare and contrast celestial observations described by others. Therefore, to ensure reliable identification, notation and communication, naming schemes had to be memorable and resistant enough to stick in the minds of users pertaining to different nations, religions and languages. Nomenclatures also needed to hold currency for an extended period of time.

Designing a lunar nomenclature was a similar challenge to the one that faced those seventeenth-century astronomers dedicated to stellar mapping. Johann Bayer voiced the need for an unbiased universal system of numerical notation for stellar identification in his elaborate constellation atlas Uranographia.Footnote ¹⁵ In his legacy, Johannes Hevelius, the author of Selenographia (Gdańsk, 1647), who was also devoted to mapping the constellations of the full northern hemisphere t, likewise alerted his readers to the need of a universal nomenclature.Footnote ¹⁶

Generally selenographers acknowledged that a variety of naming systems would hinder their desire for concerted global observation. Nonetheless, in contrast with the author of Uranographia they developed arbitrary naming strategies. Their schemes depended neither on spatial location nor on perceptible qualities such as dimension, shape, opacity or luminosity. Selenographers did not project classical mythology or explicitly use referents from Scripture to name lunar spots, as did Wilhelm Schikard and Julius Schiller, the Protestant and Catholic compilers of stellar charts who reshaped and renamed classical Ptolemaic constellations by projecting biblical figures from the Old and New Testaments.Footnote ¹⁷ However, the inseparable politics of scholarship and religion did play a role in the production, publication and dissemination of lunar nomenclatures.

Selenographers loosely grounded their nomenclatures on a comparison with geography: the language game behind the naming systems conveyed that the Moon, like the Earth, was composed of water and land formations. This image of an earthly Moon did not arise from the development of the telescope; it was a conception discussed in classical philosophy, which was reworked in Arabic and late medieval optics.Footnote ¹⁸ As Pantin and Fabbri have argued, this topos gained new significance in early modern natural philosophy.Footnote ¹⁹ The analogy deeply informed observation practices in the seventeenth century. The Earth–Moon association was emphasized for a variety of epistemic and argumentative purposes in renowned works such as Galileo's Sidereus Nuncius (Venice, 1610) and Dialogue Concerning the Two Chief World systems (Florence, 1632). In Johannes Kepler's studies in optics and lunar motion, which were relevant to the selenographic practice, theories were frequently expounded through the Earth–Moon analogy.Footnote ²⁰

The Earth–Moon analogy appropriated by selenographers carried contentious implications and spurred lengthy debates in university and courtly contexts well into the mid-seventeenth century.Footnote ²¹ It was a proposition that challenged the theory of quintessence favoured in early modern Aristotelian natural philosophy taught in universities. According to this theory, the planetary bodies that moved in spheres around the Earth were made of eternal and incorruptible matter, whereas the Earth, made of four elements, was a realm of corruption and regeneration. In this theory, the Moon's sphere was necessarily smooth and unblemished. Therefore arguing that the satellite was similar to the Earth destabilized such a cosmological system. Breaking with the tradition of quintessence, the Earth–Moon analogy could be used as an argument to support the fluidity of the heavens, the infinity of worlds, and the movement of the Earth, among other cosmological controversies. For theologians, stating that the Earth was like the Moon vastly complicated the relationship between Scripture and physics. For all these reasons, drawing parallels between the Moon and the Earth found resistance in both Protestant and Catholic circles throughout the seventeenth century.Footnote ²²

Despite these controversies, the comparison between the Earth and the Moon provided a common ground for selenography because it worked as a heuristic framework. Regardless of cosmological commitments, the simile gave observers guidelines for understanding the blurry telescopic views through optical principles. In the 1640s, John Wilkins synthesized the basic hypotheses used to translate light effects as topographic features in The Discovery of a New World. If the Moon, like the Earth, was a solid sphere covered by land and water, then the brighter parts of the Moon would be land, which reflects light, while the Moon's most opaque regions would be water, because this element refracts light. Other analogies with light behaviour on irregular surfaces triggered various nuanced hypotheses about hollows and reliefs on the satelliteʼs surface.Footnote ²³

The Earth–Moon analogy was not only an optical-research method; it also provided selenographers with a communication strategy. Large regions of the Moon were named seas and land to provide an intelligible, legible and practical base map over which smaller spots could be named, described and used for observation. Selenographers in the mid-seventeenth century did not overtly argue that the Earth–Moon analogy was a cosmological truth. Instead, this simile, with multiple possible readings, helped them make allusions and convey their own personal and collective agendas.

An instrument for longitude and peace

In May 1645 a detailed graphic of the Moon based on telescopic study came out of a Brussels printing press with the title Plenilunii Lumina Austriaca Philippica (Austrian–Philippine Luminaries of the Full Moon). It was a presented by its maker, Michael van Langren, the royal cosmographer of Brussels, as an instrument for observation: each prominent point indicated on thedisc was named so that the visual referents could be used for the determination of longitude. This device was surrounded by citations from Cicero, Seneca, Pliny and Achilles Tatius, all of which alluded to the terrestrial nature of the Moon.

Through its title and framing with classical quotes, the selenography turned a natural-philosophical hypothesis into a political conceit: the Earth-like Moon, like a mirror, reflected the light of Philippe IV (1605–65), head of the Spanish Monarchy. For this reason, Van Langren's invention has frequently been understood reductively as a cosmographer's strategy for obtaining patronage during the decline of the Spanish Empire.Footnote ²⁴ But this reading and its general historiographical assumptions should be given greater nuance. The selenography's making and publication process reveal that this technological innovation was not merely a scheme of imperial propaganda: it wasn't commissioned or rewarded by the Spanish Monarchy. Moreover, though the selenography did seek royal validation, it did so conveying the claims of Spanish subjects from an imperial periphery. It was a multilayered conceit that addressed inter-confessional audiences invested in the politics of technology, knowledge circulation and statecraft.

The topos of ‘empire conquering the heavens’ prevailed in the rhetoric of the Spanish Monarchy, to which Van Langren was under obligation. Offering the lights of the full Moon to Philip IV echoed the motto non orbis sufficit (the world is not enough) that had featured in Habsburg pageantry from the sixteenth century.Footnote ²⁵ Such rhetorical devices, moreover, had long been appealing to celestial mapping endeavours promoted by both Catholic and Protestant mathematicians and natural philosophers. In the Counter-Reformation world, the Dominican friar Tomaso Campanella advised Philip III to send astrologers to discover the stars of the southern hemisphere, to describe – and implicitly re-establish the authority of – the figure of the Holy Cross at the Antarctic pole, and to place monuments of the emperor and the House of Austria in the sky so that ‘astrology and local memory will be learnt together’.Footnote ²⁶

Creating ‘monuments’ or spaces of memory in the sky was also a rhetorical strategy in the mid-seventeenth-century Netherlandish mathematical culture. In 1642, the Capuchin Anton Maria Schyrleus de Rheita, also a selenographer, claimed to have found five new satellites of Jupiter and named them stellas urbanoctavianas in honour of Pope Urban VIII. In reponse, Johannes Hevelius, the above-mentioned Protestant astronomer from Gdańsk, countered that those bright cosmic bodies would have better been named Vladislavianas, alluding to his king, Vladislao IV.Footnote ²⁷ Back in the Southern Netherlands, the Jesuit mathematician Charles Malapert dedicated his Austriaca sidera heliocyclia to Philip IV of Spain.Footnote ²⁸ Van Langren's selenography thus rephrased the conceit associating the celestial splendour of the House of Austria with a lunar technique that would allegedly help improve the map of its empire: the luminaries of the full moon referred both to the illustrious subjects of the king of Spain and to the visible spots of the satellite that were useful for telescopic observation (Figure 1).

Figure 1.

Michael van Langren, Plenilunii Lumina Austriaca Philippica, Brussels: s.n., 1645, Leiden University Libraries, COLLBN 505-10-003, available at https://digitalcollections.universiteitleiden.nl/view/item/2137526.

Van Langren had been developing his selenography since at least 1621. His work was embedded in the context of the ongoing research pursuits for improving longitude methods in the Iberian world.Footnote ²⁹ According to his own account in a pamphlet published in Antwerp in 1644, his patron, Isabella Clara Eugenia, Archduchess of Austria and regent of Belgium (1566–1633), made lunar observations with him in the court of Brussels and took great interest in his method for the determination of longitude in 1625. With her support, Van Langren received the title of royal cosmographer of Belgium and was sent to the Royal Palace in Madrid in 1631. In the Spanish court he presented two of his longitude inventions to Philip IV, who agreed to name the most prominent spots of the Moon after the ‘luminaries’ of his reign.Footnote ³⁰ The Council of Indies promised a reward of four thousand ducats. However, after the archduchess's decease, by royal orders, Van Langren was obliged to return to the Flemish territory in 1634 without his reward.Footnote ³¹

Eleven years later, in Brussels, Van Langren finally secured the support he needed to publish his invention. With a petition to the city's Privy Council, he submitted a manuscript model which showed what the finished map would look like.Footnote ³² An annotation in this document indicated, ‘Each mountain and island, which are needed for these astronomical and geographical observations, will bear the name of a renowned person of this art and profession, one for each nation.’Footnote ³³ In his official request, Van Langren asked that the naming scheme outlined in his prototype be approved so that it would not be altered in subsequent editions.

The petition was sent to two censors, Erycius Puteanus (1574–1646) and Godevert Wendelen (1580–1667). The former, a prolific humanist and active correspondent in the Netherlandish Republic of Letters, was the successor of Justus Lipsius (1547–1606) as chair of Latin in the Collegium Trilingue of Louvain and the founder of Palaestra Bonae Mentis, a private tutoring space for students from different parts of Europe pursuing careers as civil servants. The latter was one of the most accomplished and renowned mathematicians, astronomers and chronologers in the Southern Netherlands. Both examiners were acquainted with Van Langren's work and all three had all had been invested in longitude controversies since the 1630s.Footnote ³⁴

From February to May 1645, when the selenography was finally published, Puteanus provided advice concerning the Latin texts surrounding the Moon, the printed sheet's layout and the completion of the lunar nomenclature.Footnote ³⁵ Ultimately, the naming scheme that would be crucial to observation and notation embodied the decisions that were taken through this process of collaboration. Puteanus's involvement in the project inspired him to give a lecture in Louvain in early March 1645, in which he announced the upcoming selenography and discussed the Moon's ancient names. He also expounded on past understandings of the satellite's elementary composition. Lucian's fantasies, he joked in his report to Van Langren, were not entirely unlikely. He was referring to the renowned Menippean satire that used an imaginary journey to the Moon as a vehicle through which to critique earthly politics and poke fun at terrestrial philosophers.Footnote ³⁶ In another letter, he suggested to Van Langren that they should assign a spot on the lunar surface to those ancient philosophers who defended the Earth–Moon analogy. In the final phase of the map's production, Van Langren anounced that he had decided to name the spaces distinguishing land with the word terra (referring here to both land in general and to Earth as a planet) instead of regio (region). Puteanus expressed his approval, underscoring that terra would indeed emphasize that the Moon was an Earth.Footnote ³⁷

Counter-Reformation natural philosophers tended to dissociate telescopic descriptions of the Moon from hypotheses about the satellite's earthly nature. For example, in the context of Jesuit mathematics, Christoph Clavius, François d'Aguilon (1577–1617), Christoph Scheiner (1573–1650) and Giuseppe Biancani (1566–1624) all made telescopic observations, accepted that the irregularities on the lunar surface were visible, and agreed that the Moon was not a perfect sphere. Nonetheless, they continued to defend the position that the lunar substance was quintessential, incorruptible and thus fundamentally different from the Earth's.Footnote ³⁸ Notably, however, this opinion was not unanimously held by Catholic scholars. Discussions of the Earth–Moon analogy, and of the corruptibility of the heavens more widely, echoed across printed texts and epistolary correspondence in places such as the Southern Netherlands. For instance, the above-mentioned Jesuit Charles Malapert declared that the Moon, Venus and Mercury were each of an earthly substance.Footnote ³⁹ This type of claim was linked to questions regarding the mobility of the Earth, which were openly, although carefully, discussed in Van Langren's circle of courtly and university correspondents. As Vanden Broecke has demonstrated, Wendelen, the second censor of the manuscript proof submitted to the Privy Council, was an open proponent of a geo-dynamic cosmos in public spheres as well as in his epistolary correspondence, albeit without going so far as to assert this opinion in print. His natural-philosophical commitments were known to Puteanus.Footnote ⁴⁰ The humanist in Louvain may have embraced a similar opinion, and through Puteanus this discussion would have been known to Van Langren.

However, although the Earth–Moon analogy could be read as an argument in favour of a heliocentric world system, Van Langren's selenography was not a public pronouncement in favour of that cosmology. Here, the Earth–Moon analogy perhaps more explicitly played into debates concerning the corruptibility of the heavens, an argument that was relevant to Neo-Stoic frameworks. Such Neo-Stoic associations resonated widely in the Spanish Netherlands as a privileged context for natural philosophy in its connections with religion and morality.Footnote ⁴¹

Both censors of Van Langren's selenography, Wendelen and Puteanus, were engaged in studying and adapting this philosophy to the social order of the Spanish Netherlands.Footnote ⁴² Puteanus, particularly, was personally committed to publicly defending the Neo-Stoic philosophy of his mentor and predecessor Justus Lipsius. In the collection of orations that represented the pedagogy of his Palaestra Bonae Mentis, students were invited to adopt the Neo-Stoic ethics of concord, temperance and peaceful human action in their future political offices.Footnote ⁴³ Van Langren, in turn, came from a lineage of renowned Dutch printers, globe-makers and map-makers. His father was a skilled map and globe engraver who, among many other works, corrected maps for Balthasar Moretus's revision of Abraham Ortelius's Theatrum Orbis Terrarum. Thus, trained through this family apprenticeship, Michael van Langren was well acquainted with the Neo-Stoic discourse that bridged morality and nature through the mapping tradition of Gerard Mercator, Abraham Ortelius and Franz Hogenberg. From this perspective, maps were represented as spaces for contemplation of temperate and righteous world ideals.Footnote ⁴⁴ In this context, the Earth–Moon analogy acquired broader connotations that were not openly or necessarily committed to argumentative claims concerning the Earth's mobility.

The Earth–Moon analogy that supported this lunar nomenclature was used by Van Langren and Puteanus as a scholarly exercise that would give moral and political import to a mathematical instrument. The Neo-Stoic discourse was conveyed through the names attached to the lunar areas that were not ‘seas’. Puteanus convinced Van Langren to name the regions considered ‘land’ as spaces of virtue and suggested Terra Honoris, Terra Virtutis, Terra Scientiae, Terra Laboris, and Terra Pacis.Footnote ⁴⁵ This philosophy was further reinforced by the placements of the classical citations that surrounded the selenography, and most explicitly through the famous excerpt associated with Stoicism from Book VII of Seneca's Natural Questions announcing, ‘The time will come when careful study over long periods will bring to light things which now lie hidden’, set at the bottom right of the lunar disc.Footnote ⁴⁶ In the printed broadsheet, the viewer of the map would read such quotation right below ‘Terra Pacis’. This visual strategy strengthened associations between the astronomical instrument and its political time.

In 1645, when Pleniluna Lumina Austriaca Philippica came off the printing press, peace was a pressing political issue in the context of the wars between the Spanish Monarchy and the Dutch Republic.Footnote ⁴⁷ Puteanus had long advocated for a truce in his pamphlet Statera pacis et belli, later included in Dissertationes de induciis belli Belgici, both published in Leiden in 1633.Footnote ⁴⁸ The selenography, published more than ten years later, can be read as a continuation of his plea for peace. On this occasion, the argument was made visually, through a rare image that was also an instrument for scientific observation and communication.

Through its nomenclature, the selenography conveyed ideals around which its potential users and collectors, and even critics, could coalesce in the context of violent religious upheavals. Conveying Neo-Stoic philosophy through the names of lunar locations turned a technical necessity (giving memorable identifiers to observation and notation spots used for observation) into a rhetorical conceit integral to a commentary about Netherlandish and European politics around 1645. About 50 per cent of the names inscribed in the selenography evoked a complex political network of Italian dukes; electors of the Holy Roman Empire; and French, Danish and Polish sovereigns and diplomats who participated directly or indirectly in the peace negotiations to end the Thirty Years War, which coincided with the timing of the map's publication. Consider, for instance, the spots bearing names of the ambassadors who met in Münster and Osnabrück: Count Maximilian Trauttmansdorff from Austria, Johan Oxenstierna (1611–57) from Sweden, Gaspar de Bracamonte Guzman (1595–1676) from Spain, Henri de Valois–Longueville (1595–1663) from France, Isaak Volmar (1582–1662) from the Austrian imperial delegations, Fabio Chigi (1599–1667), the papal legate who became Pope Alexander VII, and Alvise Contarini (1601–84) of Venice. Placing these names, as well as those of the Catholic Italian princes, alongside the Protestant electors was Puteanus's design.Footnote ⁴⁹ In this way, the naming strategy for purportedly universal astronomical observation and notation also created a communication instrument about and for local politics.

Names of mathematicians and natural philosophers embedded in the religious and political turmoil were also clustered across the disc. Some were grouped through regional identity or political association: Dutch scholars such as Guerrit Janszoon Voss (1577–1649), Caspar van Baarle (1584–1648), Daniel Heins (1580–1655) and Constantyn Huygens were acknowledged in Terra Sapientiae; Puteanus, Jean della Faille (1597–1652) and Govaert were located in Terra Temperantiae around the large macula on the left side of the Moon. The spots containing Dutch humanists were scattered around Mare Eugenianum (after Van Langren's patron), Mare Belgicum and Sinus Batavicus (the Latin toponym for the Netherlands), creating a visual allegory of an undivided Northern and Southern Netherlands. Patronage on a local scale was also significant: a small circle touching the edge of that region referred to the patron who facilitated this publication – Manuel de Moura y Cortereal (1590–1651), governor of the Spanish Netherlands from 1644 to 1647 and a key figure in the early Münster peace negotiations. The spot given to this patron was an important reference point in lunar observation practices.

In this way, the nomenclature was a technical and rhetorical instrument that could ostensibly speak directly to its audience. It invited the reader to engage in the visual games of seeing who was located where and why. Some names were clustered by nationality or occupation, but this was not a rule of thumb. Ambiguity was used to arouse curiosity in the reader. Puteanus's letters to Van Langren do not suggest that this purposefully loose criterion was considered an obstacle to making a reliable notation and observation scheme.

Puteanus's investment in local politics and pedagogy reveals some crucial decisions in the establishment of the nomenclature. He did not hide his motivations from Van Langren: one of his sons, Andreas, was an army officer who wanted to be promoted to captain in the division of Octavio Piccolomini, Duke of Amalfi and commander of the Spanish forces in the Netherlands. Thus he asked Van Langren if the name of his illustrious son could be inscribed south of Sinus Batavicus. In another letter, he informed the cosmographer that there was a distinguished diplomat who had participated in the Italian peace treaties, in the papal conclave of 1644, and was strategically located in the papal court of Innocent X. Such gentleman was willing to be the primary distributor of the map in Rome and – as it transpired towards the end of the note – was also his son-in-law. He also asked for a spot to be named after an alumnus of his Palaestra, Jerzy Ossoliøski (1595–1650), who was Great Crown Chancellor of the Kingdom of Poland.Footnote ⁵⁰ The spot ‘Ossolinski’ was ultimately inscribed in Terra Iustitiae. Beyond these circumstantial requests that reveal Puteanus's investment in affairs ranging from the papal conclave to the peace negotiations for the Eighty and Thirty Years Wars, the lunar nomenclature was an ingenious strategy for displaying political relations across ecclesiastic, civil and scholarly spheres in Louvain and the courts of Brussels, and beyond. Many names legible on the Moon map also featured in Puteanus's published correspondence collected in Epistolarum Apparatus.Footnote ⁵¹ Sociability was built into the selenography because gaining social credit would help secure its reception amongst potential users, collectors and patrons.

Beyond the turmoil of European politics, Van Langren and Puteanus also aspired to reach high ecclesiastics and missionaries around the world through their connections with the Society of Jesus, the clearest institutionally identifiable group in the lunar map.Footnote ⁵² To engage this audience they emphasized the selenography's function as a unique instrument for a new method for the calculation of longitude that could be useful to apostolic missions. The plan was that missionaries would carry out observations of lunar eclipses with the selenography and Van Langren's instructions. They would send their results back to the cosmographer major of the Council of Indies and he, in turn, would convey the observations to Van Langren.Footnote ⁵³

Well-placed intermediaries such Jean della Faille, an Antwerpian professor of mathematics at the Imperial College in Madrid and cosmographer major of the Council of Indies, helped conceive this plan. Della Faille had collaborated with Van Langren in longitude research since the 1630s, so in 1645 he spread news of the publication. Notably, he announced Van Langren's invention to the papal nuncio in Spain. The diplomat was delighted, wrote della Faille to Van Langren, and offered to send the instructions for calculating longitude with the selenography throughout the world. Using the circuits of Jesuit bureaucracy for this distribution would drastically reduce the costs of dissemination. Additionally, the Jesuit underscored, it would be possible to use the upcoming papal election in Rome as an opportunity to distribute the paper moons amongst Jesuit procurers (delegated mission administrators) across the West Indies.Footnote ⁵⁴ Van Langren and Puteanus wanted the nomenclature to be ecumenical and, at the same time, targeted these particular audiences in Catholic circuits to secure its wide distribution amongst other colonial instruments of confession.

As this shows, lunar nomenclature was an observation and notation scheme that was made to speak to its desired users, collectors and channels of distribution. It was designed with the aspiration of pleasing a wide range of audiences, so that it could be accepted and used for collective observation. At the same time, it also materialized personal and local interests. Heavily rhetorical, it was an encoded allegory: both a plea for inter-confessional peace and a mathematical instrument for religious colonization that would further the prestige of its makers.

A lunar observation language for the legitimation of astronomy

In 1651, six years after Van Langren's map was published, Giambattista Riccioli published the Almagestum Novum.Footnote ⁵⁵ This work was part of an ongoing Counter-Reformation project to produce Catholic encyclopedias of ancient and modern knowledge, such as Antonio Possevino's Bibliotheca Selecta. Both Riccioli's and Possevino's scholarship emphasized the significance of the mathematical sciences as tools for theology.Footnote ⁵⁶

Riccioli, who focused on astronomy, would update the Epitoma in Almagesti Ptolomei (Epitome of Ptolemy's Almagest), completed by Regiomontanus (1436–76) and published in Venice in 1496.Footnote ⁵⁷ It would also provide a modernized alternative to the most esteemed seventeenth-century annotated edition of Sacrobosco's Sphere (the reduced Latin version of Ptolemy's Almagest used as a textbook in universities from the thirteenth century) produced in the Catholic world by the Jesuit Christoph Clavius.Footnote ⁵⁸ Within the vast body of knowledge that Riccioli sought to represent in his ambitious compilation, the Moon had a central role: it was the unruly luminary which, adequately described, would yield better data for measuring the cosmos and correcting chronology.Footnote ⁵⁹ Producing a more accurate selenography would provide astronomers with a powerful tool for better observations and informed theory.

By the time the work was published, Riccioli had taught logic, physics and metaphysics in the College of Santa Lucia in Bologna for fifteen years. References to the process of producing the Almagestum Novum are found in his correspondence with a censor of the Collegio Romano, written most likely in December of 1646.Footnote ⁶⁰ Riccioli was asked to submit a section of the book detailing his own inventions (quam de propiis inventiis inscribit).Footnote ⁶¹ Censors wanted to know if he would add anything new to eminent masters (artifices) such as Tycho, Kepler and Lansberg. They also wanted to know precisely which instruments and methods Riccioli used in his astronomical observations of the motion of heavenly bodies. The censor's requests did not imply an institutional condemnation of the works of Protestant astronomers but instead reflected a complex process of regulation practices to control printing within mid-seventeenth-century Jesuit bureaucracy.Footnote ⁶² Riccioli replied in detail. He assured his censor that it was not his intention to put forward his own inventions, but to revise all existing astronomical knowledge through instrumental practices in order to reconcile what could be reconciled, and to assess what could not, providing clear criteria on either side to justify the position and ensure that anyone could follow their preferred hypothesis.Footnote ⁶³

Riccioli's reply to the censor's examination is, in a nutshell, the ethos of both the New Almagest and his new selenography. Like every other chapter of the volume, his selenography was driven by a spirit of collection, revision, correction and synthesis. It was presented in Book 4, dedicated to the Moon, following the order of Ptolemy's Almagest, as an instrument made to improve the quality of lunar libration observations. First, the Jesuit aimed to evaluate all available studies on the nature and motion of the satellite (Figure 2).Footnote ⁶⁴ Following arguments by Christoph Clavius, Christoph Scheiner and François d'Aguilon, he concluded that, though the Moon did receive reflected light from the Sun (like the Earth), the satellite was nonetheless made of celestial, incorruptible matter. Thus he denied Earth–Moon analogy and disassociated his work from theological controversies on the matter.Footnote ⁶⁵ This attitude was further reinforced by a verbal statement inscribed at the heading of his new selenography: ‘Nec homines lunam incolunt. Nec Animae in Lunam migrant’ (‘Men do not inhabit the Moon; souls do not migrate to the Moon’).

Figure 2.

‘Figura pronomenclatura libratione lunari’, in Giovanni Battista Riccioli, Almagestum Novum, Bologna, 1651, between pp. 204 and 205. Courtesy of Linda Hall Library of Science, Engineering & Technology. Available at https://catalog.lindahall.org/discovery/delivery/01LINDAHALL_INST:LHL/12100908460005961.

Francesco Maria Grimaldi (1618–1663), who studied with Riccioli in the Jesuit colleges of Parma and Santa Lucia and eventually became his closest collaborator, carried out the technical endeavour of comparing observations made through different telescopes and with the best available printed selenographies (Figure 3).Footnote ⁶⁶ Riccioli and Grimaldi were concerned with consensus: they wanted their readers to know that their selenography was made through a process of collection, comparison, synthesis and revision with every telescope and selenography that they could procure. The fold-out engraving that presents their project communicated their methodology to their audience. The heading reads

Figure 3.

‘Selenographia P. Francisci Mariae Grimaldi Soc. Iesu’ in Riccioli, Almagestum Novum, op. cit., between pp. 204 and 205. Courtesy of Linda Hall Library of Science, Engineering & Technology.

The new selenography was both an original conceit and a highly synthetically encoded tool. In it, Riccioli and Grimaldi presented a nomenclature that acknowledged but did not reproduce the schemes of their predecessors. They used geographical terminology to generally classify lunar regions as oceans, seas, islands, land and so on, but noted the Earth–Moon analogyʼs problematic relation to exegesis. Though they kept some names from Van Langren's nomenclature, they did not develop their system based on patrons or prominent members of the Republic of Letters. Instead, they erected their nomenclature upon their medical–astrological and astronomical tradition, and included names of scholars whose work informed the Almagestum Novum.Footnote ⁶⁸

Riccioli and Grimaldi examined the rhetorical possibilities that the selenography and its nomenclature could offer to its users. They resorted to mnemotechnical strategies of spatially organizing and visualizing clusters that related thematically. First, in order to function as an observational instrument, the circle was divided in into octants so that the main planetary configurations (conjunctions, oppositions and syzygies) could be easily recorded diagrammatically over the circle. Second, the largest divisions between bright and shaded spaces of the lunar disc were outlined to contain key observational spots – as with other contemporary selenographies. Then, those particular spots were further crafted to function as parts of a diagrammatic mnemotechnic device with referents to the history of astronomy. The establishment and distribution of the lunar nomenclature was likely inspired by the circular diagrams produced within the tradition of Isidore of Seville's De Natura Rerum. These figures, which were used and reappropriated widely from late antiquity to early modernity, served to organize, sometimes by dividing and classifying, elements of different doctrines or ideas in order to reveal their contradictions.Footnote ⁶⁹

Instead of using the Moon to convey cosmological possibilities and political ideals, as in Van Langren's map, Riccioli and Grimaldi projected lunar scholarship. They drew the basis of their naming system from classical and medieval medico-astrological traditions, through which the closest celestial body to Earth was understood as an agent that affected meteorology, behaviour and health. For instance, users would record observations relative to the largest dark region of the lunar disc in Oceanus Procellarum (the Sea of Storms), which was Riccioli's equivalent of Oceanus Philippicus. Surrounding this area, the nomenclature for smaller spaces conveyed a juxtaposition of medical and meteorological imagery: the Peninsula Deliriorum (Peninsula of Madness) and Peninsula Fulgorum (Peninsula of Lightning), Mare Humorum (Sea of Humours), Sinus Epidemiarum (Bay of Diseases), Mare Imbrium (Sea of Rain) and Insula Ventorum (Island of Winds). With these signifiers, the western hemisphere of the Moon conveyed decline. Negative attributes continued towards the north, with signifiers alluding to cold and death. Such connotations were counterbalanced on the eastern side of the disc with positive qualifiers such as tranquillity, fecundity and pleasantness, through Mare Serenitatis (Sea of Serenity), Mare Tranquilitatis (Sea of Tranquility), Mare Nectaris (Sea of Delight) and Mare Vigoris (Sea of Vigour). The nomenclature poetically evoked and repurposed signifiers associated with traditional lunar medicine. Those referents were known widely across universities, courts and popular culture in Europe and beyond through practice and early modern almanacs, such as those printed in Bologna from the fifteenth century.Footnote ⁷⁰

Over that surface, the Jesuit mathematicians conjured up names from a canon of scholars pertinent to the history of astronomy. Riccioli explained that, much like a diagram, the disc was divided into octants that organized physicoastronomers through chronological, philosophical or party (secta) associations.Footnote ⁷¹ The binomial physicoastronomers is intriguing: it is found but once in the entire text and Riccioli did not clearly explain what he implied. However, the Jesuit seemed to be proposing a reorganization of the canon in which natural philosophers (physici) and astronomers (here distinguished from mathematici, astrologi and cosmographi, as celestial observers were broadly defined in the early modern period) were blended into one and the same disciplinary classification.

Such a proposition was unusual considering the official distinctions between natural philosophy and mathematics adopted in the politics of the Counter-Reformation and Jesuit teaching. Astronomy was traditionally considered a mathematical science concerned with physical phenomena and quantity, not causes; whereas ‘physics’, or natural philosophy, sought to reveal causes and essential natures. In the Thomistic–Aristotelian framework, the mathematical language that supported astronomy was viewed as abstract and alienated from physical reality, bearing no relation to natural causes. Geometrical demonstration, moreover, was viewed by theologians and natural philosophers as an arbitrary construction that did not resist syllogistic reasoning. This led to a distinction of mathematics and physics in the Jesuit curriculum known as the ratio studiorum.Footnote ⁷² Yet, in the new selenography, which places natural philosophers within a scheme that alludes to astronomy's history, a new place for the celestial discipline is advanced: as Riccioli argues in the book's preface, astronomy was a tool for natural philosophy that ultimately served theology.Footnote ⁷³

The nomenclature's spatial organization was thus a thematic and chronological account of the history of astronomy that included natural philosophers. Named observation points followed a clockwise orientation, reading from left to right. The first and second octants clustered designated markers relating to classics such as Plato and Aristotle. In the third and fourth sections, Riccioli and Grimaldi grouped ancients such as Manilius, Vitruvius, Pliny and Macrobius, with mythological or literary characters, such as Atlas, Hercules, Hermes and Menelaus. The sixth octant represented Ptolemy, Albategni and Alphonsus, alongside sixteenth-century authors of cosmographies who elaborated on the writings of those scholars, such as Gemma Frius, Oronce Fine and Francesco Barozzio. In the fifth, sixth, seventh and eighth octants, modern astronomers with differing cosmological attitudes were scattered around. Riccioli deliberately joked that, in Oceanus Procellarum, Protestants such as ‘Copernicus, Rheticus, Maestlin, Rheinhold and other of their party … swam around the islands owing to the instability of the earth that they affirmed’ (Figure 4).Footnote ⁷⁴

Figure 4.

Detail of the protestant astronomers ‘swimming’ amongst the islands of Oceanus Procelarum.

As Protestant Copernicans were placed in a region signifying turbulence and conflict, a number of scholars have suggested that the Jesuit was either presenting a condemnation of the heliocentric world system, or insinuating his crypto-Copernicanism.Footnote ⁷⁵ Yet this image was not intended to convey Riccioli's personal cosmological commitments in any explicit way. Here, Riccioli is not arguing for a particular world system (he does so explicitly in the second tome of the Almagestum Novum).Footnote ⁷⁶ As Renée Raphael's analysis of student notebooks in Jesuit colleges has shown, heliocentrism, for instance, was taught in courses of mathematics in order to instruct students in the defence of doctrines traditionally associated with their institution.Footnote ⁷⁷ This hypothesis and its proponents were discussed in courses of mathematics, to train students to debunk the model, at the very least. The nomenclature embedded in the selenography was a means of visualizing different controversies. Designing the graphic in this way aligned with the Jesuit pedagogy outlined in the Ratio Studiorum, in which images (verbal, pictorial, exegetical, rhetorical, poetic, to mention examples from a wide and fluid topology) were given an educational, rhetorical and hermeneutic function.Footnote ⁷⁸

One of the main objectives of Almagestum Novum was ‘to be a library of universal ancient and modern astronomical knowledge, including associated controversies, for the members of the Society of Jesus and others who did not possess books on those subjects or who did not have the leisure to read them’.Footnote ⁷⁹ This aim was extended to, supported by and embedded in the new selenography. Every name on the map can be cross-referenced with the Almagestum Novum's two prefatory indexes, one chronological and the other alphabetical, which collected dates and biographies of astrologers and astronomers, scholars ranging from Zoroaster to Riccioli. In this sense, the selenographic nomenclature was not just a celestial observation instrument but also a reading tool for internal reference within the vast compendium in which it was published.Footnote ⁸⁰ The selenography, as a visual index for Riccioli's history of astronomy, conveyed a storehouse of knowledge. Understood in this way, it was useful as a learning or memory aid for students when they were challenged to discuss and defend their institution's cosmological commitments in different settings, such as the private courses that supplemented the Jesuit syllabus.Footnote ⁸¹

Moreover, the nomenclature, which is a highly rhetorical and technical artefact, gives a prominent place to mathematical teaching in Jesuit institutions, as in Van Langren's case. That is, the selenography was a space of recognition for Jesuit mathematicians in Bologna, where Riccioli himself taught. Framed within the sixth and eighth octants of the discseventeen of the forty-nine lunar spots represented members of Jesuit Colleges. Thus in this new lunar observation scheme was inscribed a particular sociability that acknowledged institutions, confessional circuits of knowledge circulation, and master–apprentice relations, as discussed above in the Brussels printed lunar map. As in Van Langren's case, this selenography, within or independent of its book, travelled beyond Bologna and Jesuit European circuits to the New World and provided both a technical and a rhetorical instrument to its readers in missionary colleges and colonial courts.Footnote ⁸²

Universal enough

Selenographies cannot be reduced to visual renderings of verbal statements concerning cosmological beliefs or to disembodied epistemic images that substituted telescopic views of the Moon through credited virtual technologies. These graphics were astronomical paper instruments created to work within a wide scope of knowledge systems and users. Ingeniously made, these tools mobilized knowledge through lunar nomenclatures that were technical, rhetorical and political.

Mathematics, religion and politics were aligned and articulated in the nomenclatures created by Van Langren, Puteanus, Riccioli and Grimaldi, in a reflection of early modern understandings of the uses of astronomy. As discussed in the two case studies, technical and rhetorical aspects of these schemes were mutually embedded and intertwined within the spaces and actors of scientific practice. Lunar nomenclatures were tools for observation and notation that functioned, simultaneously, as spaces of social and institutional recognition, as a didactic tools and as emblems of political and epistemic ideals. Lunar nomenclatures, selenography's key observation notation and communication devices, were designed through their makers’ awareness of the interconnectedness between technical research, social order, the politics of publication, competition, and collaboration in knowledge making.

The selenographies by Riccioli and Van Langren studied in this essay were unique graphical artefacts made in the fragile times of war and peace following the Thirty Years War. Religious considerations did not determine the technical function of these paper instruments, but they did play a role in the decisions taken to create mnemotechnical devices for lunar observation. Religious audiences, such as the Society of Jesus, provided channels of distribution for selenography and were evoked in the nomenclatures themselves. Selenographers were aware that with their naming schemes, their observation tools could be used in apostolic missions as instruments for imperial mapping. However, their nomenclatures were contrived to work across religious divides.

Through their nomenclatures, selenographers wanted their instruments to be universal enough. They aspired for them to be ecumenically received, yet they also desired that their artefacts speak to particular audiences who would extend their technical, epistemic, and political agendas. Ultimately, selenographers such as Van Langren, Riccioli and Grimaldi were self-conscious instrument makers who endeavoured to make efficient technical aids for an extended and diversified network of users. At the same time, they infused their paper technologies with a level of irony, ambiguity and open-endedness, and even a sense of humour which, like the Moon, resists being fully captured.