Abstract
From a comparison with calculation of the dates and descriptions of the allusions to lunar and solar eclipses recorded in the Anglo-Saxon Chronicle, we confirm the identifications of the eclipses given by Swanton in his 1996 translation and annotation. The details of the analysis on which this is based are given in the supplementary material published as an appendix in the on-line edition of the Journal.
Keywords
Introduction
Twenty allusions to lunar and solar eclipses in the period AD538 to 1140 are cited in the various extant manuscripts of the Anglo-Saxon Chronicle. The dates of these eclipses provide an independent, absolute check on the historical dating in the Chronicle, which are recorded in the Julian calendar. These dates have already been checked and amended by previous investigators, and the suggested amendments can be found in the footnotes given in the monograph by Swanton. 1
The aim of this research note is to confirm or otherwise adjust previously published amendments of the dates in the Chronicle. This is achieved by comparing with modern computations the supplementary information in the reports regarding the local time and description of the eclipses. Our computations in the Appendix to this paper incorporate the latest knowledge of past changes in the rate of rotation of the Earth, measured by the parameter
Our main source of the eclipse records is Swanton. 3 We have also consulted the texts published in the original Anglo-Saxon by Bately 4 and Irvine. 5 Most of the records are to be found in the Peterborough manuscript 6 but a few are in the other manuscripts. The manuscripts and geographical co-ordinates of the five places associated with them are listed in Table 1, and the dates of the eclipses can be found in Table 2.
The positions of the places associated with the manuscripts.
[Alphabetic] codes of the manuscripts as in Swanton. 7
Latitude and Longitude are given in degrees.
Comparison of manuscript (MS) dates with the calculated dates.
The disparities in the manuscripts are shown in
The correct dates are given under the ‘Calculation’ column.
The detailed analysis of the 11 lunar and nine solar eclipse records in the Chronicle are given in the Supplemental Appendix, which is available in the online supplement to this paper. By way of illustration, we give here an example of the depiction and discussion of one of the lunar and one of the solar eclipses.
Lunar eclipses
We refer the reader to the plot of AD734 (Figure 1) as an illustration of the visual aspects of a lunar eclipse relative to the observer’s horizon. We use these representations in our discussion of the individual lunar eclipses in the Supplemental Appendix.
Total lunar eclipse of AD 734 January 24, showing the progress of the eclipse in the sky at 30 minute intervals.
Due to the diurnal rotation of the Earth, the celestial sphere rotates from east to west in the course of the day. Thus, the Moon and the Earth’s shadow move from left to right relative to the observer’s horizon in the figure. Meanwhile, the Moon also moves slowly in the opposite direction relative to the shadow due to its monthly orbit around the Earth, traversing its own angular diameter (0°.5) in about an hour. The figure shows the progress of the eclipse in the sky at 30 minute intervals. Each image shows the position of the Moon relative to the Earth’s shadow at that time. The Moon entered the shadow from the right at an altitude of about 55° at 1:15 am local time, and emerged from the left at an altitude of about 25° at 4:55 am.
The angular diameter of the terrestrial umbral shadow at the lunar distance is about 1°.4. Therefore, a maximum of
The translation of each report is taken from Swanton, 8 with the alphabetic code and page number therein. We allow for the fact that the Anglo-Saxon reckoning of the date started at sunrise, as opposed to the preceding midnight in our computed date. Where the date in the Chronicle disagrees with the reckoning on the Julian calendar, the correct date is given in square brackets.
As an example of the treatment in the Appendix, we reproduce here the discussion of AD734.
Total lunar eclipse of AD734 January 24, U1 1:15 am, U4 4:55 am
[A, p.44] AD734
Here the Moon was as if suffused with blood; and Tatwine and Bede passed away.
[E, p.45] AD734
Here the Moon was as if suffused with blood; and Archbishop Tatwine passed away, and also Bede; and Egbert was consecrated as bishop.
Just the year is given. However, January 24 is the only total lunar eclipse visible from England in that year. The Bede Continuation 9 erroneously gives the date as January 31 (see Stephenson et al. 10 ). It is not unusual for the totally eclipsed Moon to appear red. Rayleigh scattering in the Earth’s atmosphere is responsible for giving the Moon a reddish or orange hue during some lunar eclipses. The condition of the Earth’s atmosphere, including the amount of pollution and dust from storms and volcanic eruptions, can affect the shade of red the Moon takes on during an eclipse.
The year and description of the eclipse in the manuscripts are correct, and the allusion to the colour of the Moon strongly affirms totality. Therefore, there is no doubt that the record accords with the eclipse of AD734 January 24.
Solar Eclipses
A detailed discussion of the nine solar eclipse records can be found in the Appendix to this paper. The track of totality for each eclipse is used to aid the detailed analysis. We give here the example of AD 733 August 14 (Figure 2).
Track of the annular eclipse of AD733 August 14, showing the shadow at greatest phase at Peterborough. The inset shows the annular appearance of the eclipse at Peterborough at that time.
Annular eclipse of AD733 August 14
[A, E, F, pp.44, 45] 733
Here Aethelbald captured Somerton; and the Sun grew dark; … (and all the circle of the Sun became like a black shield … about nine o’clock in the morning : copied from Bede’s Ecclesiastical History and its Continuation).
Bede Continuation 11
In the year 733 (anno DCCXXXIII) the Sun was eclipsed on 14 August (XVIIII kal. Sep.) about the third hour (circa horam diei tertiam) with the result that almost (pene) the whole of the orb of the Sun seemed to be covered with a black and terrifying shield.
Only the year 733 is recorded in the Chronicle, whereas in the Continuation to Bede the correct date of August 14 and a description of central annularity are given.
The eclipse reached maximum magnitude at 8:47 am, in very good agreement with the recorded time of ‘about the third hour’, which corresponds to between 7:48 am and 9:24 am. In southern England, the eclipse was central, with 2.5% of the Sun remaining visible at Peterborough (see Figure 2). The Moon and the ring of annularity around it could indeed have been compared to a black shield on the face of the Sun. This is undoubtedly a report of the annular eclipse of AD733 August 14 as seen from southern England.
Conclusion
The comparison of the manuscript dates with calculation in the Appendix to this paper are collected together in Table 2.
Our analysis of the recorded supplementary descriptions and/or time of night or day in the reports aids the identification of 14 of the 19 allusions to eclipses in the Chronicle. We confirm that all of the identifications of the eclipses given by Swanton, 12 in his translation and annotation of the manuscripts are correct.
Allowing for the Anglo-Saxon day beginning at sunrise rather than the preceding midnight, as in our computed date, eight of the dates of the eclipses in the manuscripts agree with computation, two differ by 1 year, one by 2 years, four by 1 or 2 days and 1 differs in the month. The various reasons for these discrepancies are summarised in Table 2. Regarding the two 1-year in arrears (795, 827), Swanton, 13 points out in his introduction to the Chronicle, that the chronology is dislocated at times because a year-number was accidentally repeated and consequently the year-numbers for the following events are a year in arrears. The reverse is the case for the solar eclipse of 1133, where the year is given 2 years in advance, presumably as a result of the scribe omitting year-numbers in the preceding events.
According to the Chronicle, the total solar eclipse of AD1140 March 20 occurred around noon, when people were dining. Calculation shows that this is incorrect in respect of the time of day because totality occurred around 3 pm. Nevertheless, it is still correct in stating that people were dining at that time because it was permitted to break the daily fast during Lent at the hour of Nones, which is equivalent to 3 pm.
Supplemental Material
sj-pdf-1-jha-10.1177_00218286221097111 – Supplemental material for Accuracy of eclipse records in the Anglo-Saxon Chronicle
Supplemental material, sj-pdf-1-jha-10.1177_00218286221097111 for Accuracy of eclipse records in the Anglo-Saxon Chronicle by Leslie V Morrison, F Richard Stephenson and Catherine Y Hohenkerk in Journal for the History of Astronomy
Footnotes
Acknowledgements
The authors acknowledge HM Nautical Almanac Office and the International Astronomical Union’s Standards of Fundamental Astronomy.
Supplemental material
Supplemental material for this article is available online.
Notes on Contributors
Leslie V. Morrison worked in the fields of astrometry and the Earth’s rotation at the Royal Greenwich Observatory, 1960–1998. He has collaborated with F. Richard Stephenson on several studies of the long-term variations in the Earth’s rotation, including, Measurement of the Earth’s rotation: 720 BC to AD 2015.
F. Richard Stephenson is an Emeritus Professor at the University of Durham, in the Physics department. His research concentrates on historical aspects of astronomy, in particular analysing ancient and medieval astronomical records to reconstruct the history of Earth’s rotation, as exemplified in his book Historical Eclipses and Earth’s Rotation, Cambridge University Press.
Catherine Y. Hohenkerk worked at the Royal Greenwich Observatory from 1971 and in the late 1970’s transferred to H.M. Nautical Almanac Office (HMNAO), where she worked on the Nautical and Astronomical Almanacs. She retired from the U.K. Hydrographic Office, latterly HMNAO’s host organisation, at the end of January 2017. She is a fellow of the Royal Institute of Navigation and chair of the International Astronomical Union’s Standards of Fundamental Astronomy (SOFA) Board. She collaborated with Stephenson and Morrison in the paper Measurement of the Earth’s rotation: 720 BC to AD 2015.
Notes
Supplementary Material
Please find the following supplemental material available below.
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