Johannes Kepler, astronomer 1571 - 1630 BORN: Germany Johannes Kepler, German astronomer, was an advocate of the Copernican theory and was an assistant to Tycho Brahe. On Brahe's death, Kepler was appointed his successor and consequently fell heir to his material. After making special studies of Mars, based on Brahe's data, Kepler published Astronomia nova (1609). In this classic he announced the first two of his three great laws of planetary motion. This treatise served as a bridge between Copernicus and Newton. Emperor Rudolph II, Brahe's patron, supplied the funds for publishing Astronomia nova. The Milestones of Science edition contains an engraving of the Emperor which is not found in many copies. This dedication copy is of particular interest in that it is from the library of the Archduke Ferdinand of Graz; his initials, coat of arms, and the date 1610 are on the cover, and the library entry "Bibliotheca Archii Ferdinandi" is on the title page. Another page shows the diagrams of the theories of Copernicus, Ptolemy, and Tycho Brahe, the latter being a compromise between the former two. His studies were further facilitated by the Galilean telescope and the invention of logarithms by John Napier. Several years later in Harmonices mundi (1619) he announced his third law of planetary motion. Bound with the Harmonices mundi is the second edition of one of Kepler's most important works, Prodromus dissertationum cosmographicarum (1621; first edition, 1596). It contains his recognition of the fact that there must be a regularity in the movements of the planets and their distances from the sun. This edition had some revisions which Kepler had found according to his three laws since the first publication. A third book is bound with the Harmonices mundi which is a reply to Robert Fluud, the Oxford Rosicrucian, who had attacked Kepler's theories on musical harmony. The 1622 edition is titled Pro suo opere Harmonices mundi apologia. In 1627 Kepler issued the Tabulae Rudolphinae, based on data supplied by Brahe in reference to 777 stars. These tables remained the foundation of all planetary calculations for over a century. Also of importance is the table of logistic logarithms, Kepler's own invention, and that of refractions. The book has an elaborate frontispiece containing figures of Hipparchus, Copernicus, Brahe, and Ptolemy in consultation.