Peurbach's planetary theories. Title page to Commentaria in Novas Theoricas Planetarum Georgii Purbachii (Commentaries on George Peurbach's New Theories of the Planets, 1556) by the Austrian astronomer and scholar Erasmus Oswald Schreckenfuchs (1511-1579). The text is in Latin, with the author's name at top, followed by the title and a description of the contents. The artwork is of one of Purbach's models, while at bottom are publication details. Georg von Peuerbach (1423-1461) was an Austrian astronomer whose 1472 work on planetary theories was an attempt to reconcile the theories of Aristotle and Ptolemy.