Austrian astronomer and mathematician who attempted to refine the Ptolemaic system with the use of sine tables written in Arabic numerals. He published his "new theory of the planets" in Theoricae Novae Planetarum, which contained a cosmological construction of the celestial spheres (which he believed to have solid reality). It became the primary astronomy textbook, replacing The Sphere. He was commissioned to translate the Almagest. He collaborated with his pupil Regiomontanus, who added a knowledge of Greek to Peurbach's understanding of Ptolemy's mathematics. Together, they produced the Epitome of the Almagest, the clearest rendering of Ptolemy's work yet translated. Peurbach also attempted to refine the Alfonsine Tables and Ptolemaic system with the use of sine tables using Arabic numerals, which had been introduced by Fibonacci but had not yet been universally adopted.