Tycho Brahe (1546-1601) is considered the greatest astronomer prior to the introduction of the telescope. His observations of a nova in the constellation Cassiopeia in 1572 brought him fame and secured funding for building a very expensive observatory on the island of Hven close to Copenhagen, Denmark. The observatory employed over 100 scientific assistants and was the first dedicated astronomical observatory built in Europe. Around 1595 the Danish king, Christian IV, cut his support in order to afford a larger Navy, and in 1597 Tycho left Denmark with his considerable collection of scientific instruments and his data. He settled down in Prague where he took in Johannes Kepler as an assistant. Upon the death of Tycho in 1601 Kepler inherited the data which were key to the subsequent formulation of Keplers three laws. Although Tycho Brahe could not fully accept the heliocentric cosmology, his work is nevertheless a critical element in the Copernican revolution started by Nicholas Copernicus (1473-1543) and completed by Isaac Newton (1643-1727).