It is undocumented where he learned his clockmaking skills, but eventually he became the most innovative clock and scientific instrument maker of his time. Among his major horological inventions were the cross-beat escapement, and the remontoire, two mechanisms which improved the accuracy of mechanical clocks of the time by orders of magnitude. This allowed for the first time clocks to be used as scientific instruments, with enough accuracy to time the passing of stars (and other heavenly bodies) in the crosshairs of telescopes to start accurately charting stellar positions.