

Kepler, a student of the "cautious Copernican" Michael Maestlin in Tübingen, used Copernicus's theory of heliocentrism as the basis for his treatise, and combined it with the observational accuracy of Tycho Brahe, whose calculations he acquired through his post as imperial mathematician to Rudolf II, following Tycho's death in Prague in 1601. Disagreement with Tycho's heirs led to delays with the publication which only commenced in the summer of 1608, once Tycho's son-in-law, Franz Tengnagel, was able to add a note to the reader regarding Kepler's deviance from Tycho's calculations. The publication was supposed to be distributed privately by the Emperor, but Kepler sold some copies to the printer in an attempt to recoup some of his salary which was in arrears.