1195-1256

English astronomer and mathematician, also known as John of Holywood or John of Halifax, whose Tractatus de sphaera (1220) helped popularize the ideas of Ptolemy (fl. 100s). In 1472 the book became Europe's first printed work on astronomy, and despite a number of errors, it continued to be widely used until the seventeenth century. Sacrobosco called for calendar reform in De anni ratione (1232), and discussed the use of the quadrant by astronomers in Tractatus de quadrante.