How did Johannes Kepler use Tycho Brahe’s observations after Brahe died?

After Tycho Brahe died in 1601, Johannes Kepler gained access to his extensive collection of observational data following a political struggle with Tycho’s heirs.123

Kepler had initially hoped to use these records to refine his own cosmological theories, but he found that the data required significant analysis to be put into a usable form. He focused specifically on the observations of Mars, as its large orbital eccentricity made it ideal for testing deviations from circular motion.1

When Kepler attempted to model the orbit of Mars using traditional circular paths and Ptolemaic laws, he encountered a discrepancy of 8 minutes of arc compared to Tycho’s precise observations. Believing that Tycho’s data was accurate to within 2 minutes of arc, Kepler refused to ignore this error, which forced him to abandon the ancient assumption of uniform circular motion. This rigorous empirical approach led him to discover that planets move in elliptical orbits with the Sun at one focus, forming the basis of his laws of planetary motion.1345