Endnote 15
Part I, §17, l. 6.  Ptholome.  The St. Jolm's MS. has ptolomeys almagest.  `Almagest, a name given by the Arabs to the megalh suntaxiz, or .great collection, the celebrated work of Ptolemy, the astronomer of Alexandria [floruit A.D. 140-160].  It was translated into Arabic about the year A.D. 827, under the patronage of the Caliph Al Mamun, by the Jew Alhazen ben Joseph, and the Christian Sergius.  The word is the Arabic article al prefixed to the Greek megistus, "greatest", a name probably derived from the title of the work itself, or, as we may judge from the superlative adjective, partly from the estimation in which it was held.' -- English Cyclopaedia; Arts and Sciences, i. 223.  The Almagest `was in thirteen books.  Ptolemy wrote also four books of judicial astrology.  He was an Egyptian astrologist, and flourished under Marcus Antoninus.  He is mentioned in the Sompnour's Tale [D 2289], and the Wif of Bathes Prologue, ll. 182, 324.' -- Warton, Hist. E. P. ii. 356, ed. 1871.  The word almagest occurs in the Milleres Tale, near the beginning (A 3208), and twice in the Wif of Bathes Prologue (D 183, 325).

Chaucer says the obliquity of the ecliptic, according to Ptolemy, was 23° 50'.  The exact value, according to Ptolemy, was 23° 51' 20"; Almagest, lib. i.c. 13.  But Chaucer did not care about the odd degree, and gives it nearly enough.  See note to ii 25. 19.