Astronomical Images : Position of the centres of the eccentric spheres of the Universe

Johannes Kepler

Astronomical Images

<p style='text-align: justify;'>Plates [<i>Tabellae</i>] 1, 2, 4 and 5 of Johannes Kepler's <i>Mysterium cosmographicum</i> were, as Gerd Grasshoff has shown, designed by Kepler's collaborator in production of the work, his former teacher at Tuebingen Michael Maestlin, who had insisted on the need for diagrams to convey the central arguments of the work. They represent the specificities of the Copernican planetary models as calculated by Maestlin on the basis of Reinhold's <i>Prutenic Tables</i>. Plate 5, seen here, together with Plate 4, shows the thicknesses of the planetary orbs required to accommodate their eccentric paths. It shows the maximum and minimum distances of the planets from the Sun, crucial for the confirmation of Kepler's spacing of the planetary orbs in accordance with their placements within and around the regular solids. The diagrams on the left and right show the directions of the apsides (lines joining the points of maximum and minimum distance) in the times of Ptolemy (140 AD) and Copernicus (1525 AD), respectively. Kepler explicitly credits Maestlin both with the calculation of the distances on the basis of Reinhold's <i>Prutenic Tables</i> and with preparation of Plate 5. In fact, as Max Caspar and E. J. Aiton have shown in detail, the figures that Kepler gives in the accompanying text (largely derived, with a few slips, from Copernicus) are inconsistent with Maestlin's - ironically, given that Maestlin's figures confirm Kepler's model rather better than his own.</p>