This short note responds to a recent article on “Occultation Records in the Royal Frankish Annals for A.D. 807: Knowledge Transfer from Arabia to Frankia?” by Ralph Neuhäuser and Dagmar L. Neuhäuser ( JHA 55, no. 3). It shows that, contrary to a key claim made in this article, the presence of rules for predicting solar and lunar eclipses in manuscripts associated with the so-called Seven-Book-Computus of 809 is due to the influence of the Liber Nemroth , a text with roots in the pre-Islamic Near East.
A manuscript now in Bamberg preserves the only surviving fragment of a thirteenth-century treatise on comets or 'new stars', which was written as a letter addressed by an unknown Dominican author to the Master General of his order, John of Vercelli. The present article offers the first discussion of this forgotten work, which was composed in the year after the Great Comet of 1264. Although most of the text has been lost, the inclusion of a geometrical diagram in the manuscript makes it possible to reconstruct a crucial part of its overall argument. The Dominican author was openly critical of the Aristotelian doctrine of comets as atmospheric phenomena and considered the possibility that reliable distance estimates might instead place such objects in the celestial realm. His geometrical investigation of this question is historically significant for containing the earliest known analysis of the effect of cometary distance on its observable parallax, thus anticipating aspects of Johannes Regiomontanus's seminal 16 Problems on comets.
This article is intended to serve as a supplement to the volume Medieval Latin Christian Texts on the Jewish Calendar published in 2014. It provides references to previously neglected Latin texts and/or numerical tables related to the rabbinic lunar calendar, which appear in manuscripts copied between the twelfth and sixteenth centuries. Among the material covered are comments on the Jewish calendar in some recently published computus treatises of the twelfth century and a fourteenth-century Italian manuscript containing decision trees for the year-types in the rabbinic calendar. The article also documents the thirteenth- and fourteenth-century spread of Latin tables for finding the date/time of mean conjunction (molad) according to the Jewish calendar, including those contained in a work by the Franciscan John of Pershore. In addition it covers various late-medieval calendars in which conjunction times are given in the Jewish manner of dividing the hour into 1,080 halakim.
Abstract While the study of the solar corona is barely two centuries old, and the study of its physics even more recent, the prediction of eclipses goes back much further in time. A wide variety of theories and techniques put ancient and medieval astronomers in a position to foretell the occurrence and appearance of total solar eclipses. Geographically and chronologically, the following chapter ranges from the ancient Near East to Renaissance Europe, placing a particular focus on the status of eclipses in Hellenistic Greek and later Arabic astronomy and the transmission of the relevant knowledge and tools to Latin Europe during the Middle Ages.
Two Latin sources from the years around 1300 (John of Sicily's commentary on the canons to the Toledan tables and a parchment slip documenting the astronomical activities and observations of Alard of Diest) contain brief references suggesting that Parisian scholars of this period had access to a set of astronomical tables for Tunis known as tabulae Benesac. According to the argument developed in this article, the tables in question probably corresponded to a Maghribi zij originally created by Ibn Ishaq al-Tunisi in c.1222. The article goes on to discuss the possible channels of transmission that could have brought these tables to Paris as well as the potential implications of this finding for the history of Latin astronomy in the late 13th and early 14th century. Attention is also drawn to the presence of eclipse-related material from the Muqtabas zij by Ibn al-Kammad in a Northern French manuscript of the second half of the 13th century, which was independently translated from the Arabic and accordingly does not derive from the well-known translation by John of Dumpno (Palermo, 1260).
Abstract: "Liber de wazalkora" is the title of an unpublished Latin treatise on the construction and use of the planispheric astrolabe, which appears to have been compiled in southeast Germany (Bavaria) in the second half of the 12th century. It is to a large extent derived from other astrolabe sources available in the Latin West before 1100, but also contains material that has no precedent in any of the known literature. The analysis presented in this article concentrates on the Liber de wazalkora’s section on the use of the astrolabe, which is unusual for both its extraordinary length and frequently atypical astronomical content. A study of the Arabic loan vocabulary in this section leads to the conclusion that some parts of the text were derived from an unidentified Arabic source, presumably via a Latin intermediary. How to cite: Nothaft, C. P. E. “On the Liber de wazalkora, A 12th-Century Treatise on the Astrolabe”. Aestimatio: Sources and Studies in the History of Science (2023) 4: src02 1–58. https://doi.org/10.33137/aestimatio.v4.44061
Abstract The idea of reconciling Ptolemaic planetary theory with Aristotelian natural philosophy by imagining epicycles and eccentric deferents as three-dimensional orbs or orb-segments within larger spheres is frequently associated with Georg Peurbach and his widely read astronomy textbook, the Theoricae novae planetarum (1454). This article cautions against existing tendencies to overstate the originality or revolutionary force of this work by taking a closer look at the early history of the same Ptolemaic-Aristotelian compromise in a Latin European context. Using previously unpublished or unused source material from the twelfth to early fourteenth centuries, it documents the gradual spread and acceptance of an orbicular interpretation of Ptolemy’s planetary models among astronomers and university teachers.
The idea of reconciling Ptolemaic planetary theory with Aristotelian natural philosophy by imagining epicycles and eccentric deferents as three-dimensional orbs or orb-segments within larger spheres is frequently associated with Georg Peurbach and his widely read astronomy textbook, the Theoricae novae planetarum (1454). This article cautions against existing tendencies to overstate the originality or revolutionary force of this work by taking a closer look at the early history of the same PtolemaicAristotelian compromise in a Latin European context. Using previously unpublished or unused source material from the twelfth to early fourteenth centuries, it documents the gradual spread and acceptance of an orbicular interpretation of Ptolemy's planetary models among astronomers and university teachers.
Recent research has shown that the use of astronomy as a chronological problem-solving tool has deep roots in the scholarly practices of the Latin Middle Ages, as is manifest from the writings of Marianus Scotus, Gerland, and other "critical computists" of the eleventh and twelfth centuries. This essay enlarges the existing picture by introducing a hitherto unknown epistolary treatise of the mid-twelfth century. Written in Lotharingia in 1144, this poorly preserved work documents an attempt to reconstruct the timeline of world history via techniques that had emerged within the Latin computus tradition prior to the advent of Greco-Arabic astronomy. Drawing on the so-called computus naturalis, the author performed lunar computations on the basis of observed eclipses and used them to propose new dates for the Creation and the Last Supper. He also relied on a revised estimate of the time and date of the vernal equinox, placing it on 16 March, and gave a detailed account of how this result can be derived from solar observations with a meridian line. By virtue of these methodological features, the Chronology of 1144 represents an important transitional stage between the "critical computists" and the use of eclipse-based dating methods by later scholars such as Giles of Lessines (fl. 1260).
Manuscripts in Oxford and Erfurt preserve evidence of the earliest known efforts made in Latin Europe to remeasure the eccentricity and maximum equation of the Ptolemaic solar model. The present article analyses and contextualizes this evidence, while also revisiting Ernst Zinner’s hypothesis according to which the relevant observations were made by Alard of Diest ( fl.1308).
This article surveys surviving evidence for the determination of geographic longitude in Latin Europe in the period between 1100 and 1300. Special consideration is given to the different types of sources that preserve longitude estimates as well as to the techniques that were used in establishing them. While the method of inferring longitude differences from eclipse times was evidently in use as early as the mid-twelfth century, it remains doubtful that it can account for most of the preserved longitudes. An analysis of 89 different estimates for 30 European cities indicates a high degree of accuracy among the longitudes of English cities and a conspicuous displacement eastward (by 5°–7;30°) shared by most longitudes of cities in Italy and France. In both cases, the data suggest a high level of interdependence between estimates for different cities in the same geographic region, although the means by which these estimates were arrived at remain insufficiently known.
MS Vienna, Österreichische Nationalbibliothek, 5311, fol. 137r, contains an unusual record of astronomical observations, among which are measurements of solar and stellar altitudes carried out with large quadrants in Bologna, Montpellier, and Genoa between 1305 and 1312. An analysis of this observational data reveals a high level of precision and accuracy, as the astronomer responsible achieved a mean error of only 0;2° during an extended run of measurements of solar noon altitudes made between December 1305 and March 1306. Other passages on the same manuscript page mention Johannes de Luna, a German astrologer-astronomer active in Bologna between c.1299 and 1312. References to his name in 14th-century manuscripts shed light on his involvement in contemporary attempts to correct the Toledan Tables and revise their model of precession on an observational basis.
This article surveys measurements of celestial (chiefly solar) altitudes documented from twelfth- and thirteenth-century Latin Europe. It consists of four main parts providing (i) an overview of the instruments available for altitude measurements and described in contemporary sources, viz. astrolabes, quadrants, shadow sticks, and the torquetum; (ii) a survey of the role played by altitude measurements in the determination of geographic latitude, which takes into account more than 70 preserved estimates; (iii) case studies of four sets of measured solar altitudes in twelfth-century Latin sources; (iv) an in-depth discussion of the evidence relating to altitude measurements performed in Paris in the period 1281–1290. The findings from the last part indicate that by the end of the thirteenth century Parisian astronomer had developed rigorous standards of observational practice in which altitudes were typically measured to a precision of minutes of arc and with a level of accuracy higher than ± 0;5°, and sometimes exceeding ± 0;1°.
Two Latin manuscripts in Oxford and Florence preserve diverging recensions of a previously unnoticed astronomical treatise beginning Infra signiferi poli regionem (Oxford recension) or Circulorum alius est sub quo (Florence recension). It can be shown that this anonymous text was originally intended to accompany the Tables of Marseilles in Raymond of Marseilles's twelfth-century Liber cursuum planetarum (ca. n41). While the core tables for planetary longitudes in this set were founded on Ptolemy's kinematic models, as known from the Almagest, this new source frequently deviates from the Ptolemaic norm, for instance by explicitly rejecting an epicyclic explanation of planetary stations and retrogradations. In place of the latter, it argues in favour of a heliodynamic theory inspired by Roman sources such as Pliny, which underwent certain developments in the works of twelfth-century Latin writers such as William of Conches. Rather than being wholly exceptional, these features are indica-tive of a degree of disconnect between planetary theory and computational practice in twelfth-century Latin astronomy, which is also detectable in other sources from this period.
Since the appearance of its first volume in 1993, Micrologus, a periodical published by the Società Internazionale per lo Studio del Medioevo Latino (SISMEL) under the editorial aegis of Agostino Paravicini Bagliani, has developed into a significant forum for historical scholarship on medieval ideas about/approaches bearing on the natural world and their social settings—as indicated in the subtitle Nature, Sciences and Medieval Societies. Known for its annual volumes on themes such as “the Human Skin” and “Silence”, Micrologus has maintained a consistent approach of publishing the proceedings of highly focused academic colloquia rather than going down the conventional route of a submission-based journal. A broadly similar thematic outlook combined with a greater diversity of formats has come to characterize Micrologus Library, a companion book series launched in 1998 and now exceeding 110 volumes. Its entries have included proceedings volumes, single-author essay collections, textual editions, and a few monographs.
