Alessandro Piccolomini

Alessandro Piccolomini (1508 to 1579) was an Italian humanist, astronomer and philosopher from Siena who promoted the popularization in the vernacular of Latin and Greek scientific and philosophical treatises. His treatises Sfera del mondo and De le stelle fisse of 1540 adhered to Ptolemaic theories, and De le stelle fisse contained what is generally regarded as the first printed star atlas, with charts of 47 of the 48 Ptolemaic constellations and stars down to fourth magnitude, labelled with Roman letters, a forerunner of the Greek letter system introduced by Johann Bayer over 60 years later. In his Trattato della grandezza della terra e dell acqua of 1558 he opposed the Aristotelian and Ptolemaic opinion that water was more extensive than land. At the behest of Cosimo de Medici he wrote a proposal for reforming the calendar in 1578, and in 1574 Pope Gregory XIII appointed him titular bishop of Patras and Coadjutor Archbishop of Siena. He also wrote comedies, sonnets and translations, and a lunar crater is named after him.