Toledo School of Translators
The significant early exponent of the 'circular 36,000' years method was Ptolemy and, due to the status placed upon Ptolemy by later scholars, the Christian and Muslim astronomers of the Middle Ages accepted the Great Year of 36,000 years rather than trepidation. However some scholars gave credence to both theories based on the addition of another sphere which is represented in the Alfonsine tables produced by the Toledo School of Translators in the 12th and 13th centuries. The Alfonsine tables computed the positions of the sun, moon, and planets relative to the fixed stars. The Italian astronomer Cecco d'Ascoli, professor of astrology at the University of Bologna in the early 14th century, continued to have faith in trepidation but believed it swung 10 degrees in either direction. Copernicus refers to trepidation in "De revolutionibus orbium coelestium" published in 1543.