Kepler

Johannes Kepler (1571-1630), a German astronomer, is commonly considered to be the first astrophysicist. Most of his work was theoretical rather than observational, possibly due to his poor eyesight.

Kepler is perhaps best known for his Laws of Planetary Motion: he was the first to develop a mathematical description of the movements of the planets. Much of his work depended on the high-precision observations of Tycho Brahe, for whom he worked, and later succeeded, near Prague.

Kepler is not best known as a maker of telescopes, but he did build them and improved the design. The Keplerian Telescope, the design named after him, is a refracting telescope using two convex lenses.