Comment on Kepler: The most interesting aspect of reading about the development of astronomy is learning how each pivotal figure struggled with past theories, moved forward (sometimes) in an attempt to either refute or further develop those theories, and developed a theory which would eventually be disproven by others. Kepler realized that Copernicus's math was off, but the calculations could be made more accurate by showing that the planets moved in elliptical, rather than circular, orbits. However, Kepler based his theory on perfect elliptical orbits so his calculations remained slightly off. He had not calculated in the various planetary wobbles caused by the various gravitational pulls among the planets (and other bodies moving through the solar system)that led to variations in the elliptical orbits.

But these early astronomers are amazing in how they carried out their observations and worked calculations to support their theories--and without the aid of a telescope. Galileo was just up ahead of Kepler, but I must edit here: I don't know what effect Gallileo's telescope had on Kepler's math. [Did we have to wait for Newton to factor in gravitational pull of the planets upon each other?] Or any of the astronomers preceding Galileo. Of course, that's as much a waste of time to consider as adding twenty years to Mozart's life and trying to predict how his music may have developed.