Serena added more about him.

Tycho Brahe's contributions to astronomy were enormous. He not only designed and built instruments, he also calibrated them and checked their accuracy periodically. He thus revolutionized astronomical instrumentation. He also changed observational practice profoundly. Earlier astronomers had been content to observe the positions of planets and the Moon at certain important points of their orbits, Tycho and his cast of assistants observed these bodies throughout their orbits. This resulted in a number of orbital anomalies never before noticed and were made explicitly by Tycho. Without these complete series of observations of unprecedented accuracy, Kepler could not have discovered that planets move in elliptical orbits. Tycho was also the first astronomer to make corrections for atmospheric refraction. In general, whereas previous astronomers made observations accurate to perhaps 15 arc minutes, those of Tycho were accurate to perhaps 2 arc minutes, and it has been shown that his best observations were accurate to about half an arc minute.
Tycho's observations of the new star of 1572 and comet of 1577, and his publications on these phenomena, were instrumental in establishing the fact that these bodies were above the Moon and that therefore the heavens were not immutable as Aristotle had argued and philosophers still believed. The heavens were changeable and therefore the Aristotelian division between the heavenly and earthly regions came under attack, like with Galileo's 'Dialogue', and was eventually dropped. Further, if comets were in the heavens, they moved through the heavens. Up to now it had been believed that planets were carried on material spheres (spherical shells) that fit tightly around each other. Tycho's observations showed that this arrangement was impossible because comets moved through these spheres. Celestial spheres faded out of existence between 1575 and 1625.