Austrian mathematician and astronomer who studied at the University of Vienna, then traveled through Europe lecturing on astronomy in Germany, France, and Italy. He became the court astronomer of Hungary in 1454, and professor of astronomy at Vienna. He published detailed observations of the 1456 visit of what was later named Halley's comet. He also wrote on the computation of sines and chords, and produced tables of eclipse calculations. He taught Regiomontanus (1436-1476), and they collaborated on a number of texts.