Carolingian Eclipse Rules and the 'Liber Nemroth': Some Remarks on a Recent Hypothesis

2013

This paper deals with the analysis of data obtained from observations of two sets of three lunar eclipses in the Late Medieval Islamic Period. The first trio consists of the lunar eclipses of 7 March 1262, 7 April 1270 and 24 January 1274, observed by Muḥyī al-Dīn al-Maghribī from the Maragha Observatory (in northwestern Iran), and the second includes those of 2 June and 26 November 1406, and 22 May 1407, observed by Jamshīd Ghiyāth al-Dīn al-Kāshī from Kāshān (in central Iran). The results are that al-Maghribī"s values for the magnitudes of these eclipses agree excellently with modern data, and his values for the times when the maximum phases occurred agree to within five minutes with modern values. Al-Kāshī"s values for the times of the maximum phases show a rather larger divergence from modern data, varying from about ten minutes to about one hour. The errors in all six values both astronomers computed from their own solar parameters for the longitude of the Sun at the instant of the opposition of the Moon to the Sun in these eclipses remain below ten minutes of arc. The motivation for doing these observations was to measure the lunar epicycle radius r in the Ptolemaic model. Al-Maghribī achieved r = 5;12 and al-Kāshī r ≈ 5;17, 1 in terms of the radius of an orbit of R = 60 arbitrary units. It is argued that comparing with modern theory, neither of these two medieval values can be considered an improvement on Ptolemy"s value of r = 5;15.

Medieval Worlds, 2022

Published in Medieval Worlds 17 (2022), pp. 3-58 (peer reviewed): https://medievalworlds.net/?arp=0x003ddac6 The blinding of the Byzantine emperor Constantine VI in Constantinople in August 797 and his overthrow by his mother Eirene, who then ruled as the first female »emperor« of the Eastern Roman Empire until 802, was used as legitimation for the coronation of the Frankish king Charlemagne as emperor of the Romans on 25 December 800, by contemporaries in Western Europe. Some observers in the West may have even interpreted the downfall of the Eastern Roman emperor and his replacement by a woman as sign of an impending collapse of the Roman Empire and the entire world order, as already expected (based on chiliastic calculations). We equally find indications of apocalyptic expectations in Constantinople, where Constantineʹs blinding was linked with a spectacular celestial manifestation of divine disapproval – a darkening of the sun for 17 days. In this paper, this obfuscation of the sun is compared with the description of other atmospheric and climatic phenomena in the 8th and 9th centuries, as well as before and after this period. In addition, natural scientific data is used to disprove earlier hypotheses on the physical background to this event and to present a more probable scenario (i.e., the impacts of one or more volcanic eruptions) for the darkening of 797 and other phenomena, which provided a peculiar »atmospheric« framework for the interpretation of the events between the downfall of Constantine VI and the coronation of Charlemagne by contemporaries.

Suhayl. International Journal for the History of the Exact and Natural Sciences in Islamic Civilisation 21 (2024), pp. 209–340.

Abū Muḥammad Jābir b. Aflaḥ, a 12th-century Andalusian mathematician and astronomer, is recognized for his influential work al-Kitāb fī l-Hay ᾿ a, a work today better known as Iṣlāḥ al-Majisṭī. Jābir b. Aflaḥ's al-Kitāb fī l-Hay ᾿ a is a reedition of Ptolemy's Almagest in which he also included a number of criticisms of Ptolemy's work. The present study focuses on Jābir b. Aflaḥ's criticisms of Ptolemy's theory of solar eclipses, highlighting three key objections: two on Ptolemy's choice of the mid-heaven instead of the mid-heaven of the ascendant to obtain the parallax in longitude and its effect on solar eclipses; and an additional one on Ptolemy's treatment of the lunar parallax in latitude. While two of these criticisms appear unjustified, they offer insight into Jābir's methodology and his reliance on defective or abridged manuscripts. Jābir's novel approach, particularly in his use of the new trigonometry, together with his disregard for certain celestial motions, reveal both his mathematical strength and his limitations in practical astronomy. His failure to account for the Sun's additional motion in the computations of solar eclipses further underscores his inexperience. Nevertheless, Jābir b. Aflaḥ emerges as a creative astronomer, whose work demonstrates a deep engagement with and unfrequent understanding of Ptolemy's Almagest, albeit with notable oversights in the practical aspects of astronomy.

Journal for the History of Astronomy, 2016

The eclipse of a.d. 1239 June 3 was observed at no less than 10 sites in Europe, but the one from a.d. 1354 September 17 was observed only from two European sites. In this paper, we present several new references for the a.d. 1239 and a.d. 1354 solar eclipses, most of them from unpublished Spanish documents. In particular, we study three records engraved on stones whose existence was not known until recently. Such records are very rare in the rest of Europe. The study of ancient eclipses has proven to be useful for obtaining some astronomical data of interest to modern astronomy. In particular, the analysis of these eclipses may be useful for determining a range of ΔT for the epochs.

Journal for the History of Astronomy, 2023

(paper upon request) This study analysed four records of questionable authenticity of total solar eclipses between the fourth and sixth centuries CE in Byzantine narrative sources. As it has been difficult to evaluate their credibility, they have not been utilised in modern astronomical studies. Three records originated in the fourth century, all of which have problems with accurate dating and provenance. The one remaining record concerns the total solar eclipse on 512 June 29. This study first reveals the problems with and questions around the reliability of all these records from astronomical perspectives based on the latest ΔT spline curve and recently proposed ΔT constraints. It then explores their philological and historical contexts to understand how and why these records were written.

2006

At the very beginning of his article in the Coptic Encyclopedia on the dating of inscriptions, Pierre Du Bourguet remarked, "Broadly speaking, the dating of Coptic monuments and artifacts is one of the thorniest problems in this archaeological field". 1 The purpose of this paper is to reconsider one of the rare exceptions to this gloomy generalisation, a fixed point in the Coptic record-and in Coptic palaeography-which has received surprisingly little attention in the years since it was first published, well over a century ago.

Journal for the History of Astronomy, 2019

Existing research dealing with astronomical observations from medieval Europe have extensively covered topics such as solar and lunar eclipses and sightings of comets and meteors, but no compilation of occultations of planets by the Moon has been carried out and, till now, the data have remained scattered in different publications. The main reasons for this are the small number of observations that has reached us, their limited use for calculation of parameters associated with the rotation of the Earth, and the fact that between the fifth and fifteenth centuries, the period that we consider, almost none of these observations were made scientifically, since they usually appear in narrative texts, be they chronicles or annals. Our purpose is to make a compilation of these phenomena, trying to shed light on some of the most controversial observations after examining them in their historical context. We will examine European sources, but, occasionally, we will also consider reports from...

richardcarrier.info

Surveys various ancient beliefs regarding eclipse phenomena (both scientific and superstitious).

Suhayl. International Journal for the History of the Exact and Natural Sciences in Islamic Civilisation, 2017, 2017

This paper focuses on an extract from the treatise of al-Bīrūnī (973-1048 AD) "Comprehension of the possible ways for the construction of the astrolabe", where “the plate of the eclipses” is described. This is a device that can be attached on the back side of the astrolabe. It consists of a plate, engraved on both sides, and a grid that can be attached to either side of the plate and can rotate upon it. Given the date of the lunar month, one can find the time of the moon rising and the phase of the moon, using the front side of the plate. Knowing the latitude of the moon at the opposition, one can determine whether there will be a lunar eclipse or not, using the back side of the plate, and can also estimate the magnitude, start time and duration of the eclipse. The results are approximate.