Walcher of Malvern
Walcher of Malvern, also known as Walcher of Lorraine, was the second Prior of Great Malvern Priory in Worcestershire, England, and a noted astronomer, astrologer and mathematician. He has been described as an important transitional figure, whose observations and writings reflected the transformation of the astronomy of the Latin West from its traditional focus on computing dates in the ecclesiastical calendar and studying the rudiments of Roman astronomy to the use of ancient astronomical computational methods learned from Arabic zijes and other Islamic sources.
Life and WorkEdit
Walcher was from Lotharingia, a region influenced by the new scientific ideas coming from Spain, and arrived in England around 1091. Using an astrolabe to measure the time of several solar and lunar eclipses with an accuracy of about fifteen minutes.  Based on these observations, he computed a set of tables giving the time of the new moons from 1036 through 1111, which were considered important for medical astrology. His later observations revealed significant errors in his tables, reflecting the limitations of early medieval astronomical theory. 
In his later De Dracone (ca. 1116), Walcher drew on the knowledge of Arabic astronomy that his master, Petrus Alfonsi, had brought from Spain. De Dracone discussed the motion of the lunar nodes (the head and tail of the dragon) and their significance for the computation of lunar and solar eclipses. In De Dracone, Walcher recorded angles in degrees, minutes, and seconds, although he wrote these numbers using Roman, rather than Arabic numerals.
Walcher was Prior of Malvern Priory from 1120 to 1135. Walcher's gravestone in St Anne's Chapel at the Priory Church records his abilities:
Philosophus dignus, bonus astrologus lotharingus,
Vir pius et humilis, monachus, prior hujus ovilis
Hic jacet in cista geometricus et abacista,
Doctor Walcherus; flet plebs, dolet undique clerus;
Huic lux prima mori dedit Octobris seniori;
Vivat ut in coelis exoret quisque fidelis. MCXXXV.
"In this chest lies Doctor Walcher, a worthy philosopher, a good astronomer, a Lotharingian, a pious and humble man, a monk, the prior of his sheepfold, a geometer and abacist. The people mourn, the clergy grieve on all sides. The first day of October brought death to this elderly man. May each believer pray that he may live in heaven. 1135."
- McCluskey, Stephen C. (1998), Astromomies and Cultures in Early Medieval Europe, Cambridge: Cambridge University Press, pp. 180–184, ISBN 0-521-58361-6
- Nothaft (2017, pp. 1–7)
- Nothaft (2017, pp. 15–17)
- Nothaft (2017, pp. 114–5, 240–5)
- Nothaft (2017, pp. 188–90, 268–70)
- Haskins, Charles Homer (1927), "The Introduction of Arabic Science into England", Studies in the History of Mediaeval Science, Cambridge: Harvard University Press, pp. 112–117
- Nothaft (2017, pp. 46–55)
- Nothaft (2017, pp. 194–5, 271–2)
- Nothaft (2017, pp. 194–7, 275–7)
- Nothaft (2017, p. 10) The date of 1135 was found on the original version of the marker; the present, restored, version has 1125.