Tycho Brahe produce much of his astronomical data, Tycho relied heavily on the then new technique of "prosthaphaeresis", an algorithm for approximating products based on trigonometric identities that predated logarithms. Although Tycho admired Copernicus and was the first to teach his theory in Denmark, he was unable to reconcile Copernican theory with the basic laws of Aristotelian physics, that he considered to be foundational. He was also critical of the observational data that Copernicus built his theory on, which he correctly considered to have a high margin of error. Instead, Tycho proposed a "geo-heliocentric" system in which the Sun and Moon orbited
Tadeáš Hájek is unfortunately lost now. In 1564 he received the Emperor's privilege stating that no astrological prognostication could be printed in Prague before he had seen and approved it. In 1566–1570, he served as an army doctor in Austria and Hungary during the war with the Ottoman Empire. He published his studies of a supernova in the constellation Cassiopeia in 1572. Tadeáš Hájek was in frequent scientific correspondence with the recognized astronomer Tycho Brahe (1546–1601) and played an important role in persuading Rudolph II to invite Brahe (and later Kepler) to Prague. His voluminous writings in Latin were mostly concerned with