Brahe

Tycho Brahe
Epistolarum Astronomicarum Libri
Astronomiae Instauratae Mechanica

Despite his accurate observations and measurements of the positions of stars and movements of the planets, Tycho Brahe (1546-1601) could not abandon the idea of an "Earth-centered" universe. However, his two-year long observations of the color and magnitude change of a "new star" in the Constellation of Cassiopeia's helped bring the Aristotelian theory of unchanging celestial spheres to an end. His records on this new star identify it as a supernova.

Brahe's "naked-eye" observations and the observation tools he designed proved helpful in developing the Gregorian calendar still in use today. Brahe's work also was useful to his assistant Kepler, who defended the Copernican sun-centered view and developed Kepler's laws.

Brahe is an interesting figure as he can be understood as trapped between the two worlds of geocentrism and heliocentrism.  He recognized the strengths of the Copernican system but could not entirely abandon the age-old view that the earth was at the center of the universe.  This led him to adopt a hybrid system.  For Tycho, the earth was at the center of the universe and was orbited by the sun and moon.  The sun, while circling the earth, was itself circled by the other known planets.

Brahe had astronomical instruments, built in wood, brass and iron, of every known variety. His observations and measurements through these instruments changed or improved almost every single aspect of astronomical theory.