Astronomical Images : Size of the lunar sphere

Johannes Kepler

Astronomical Images

<p style='text-align: justify;'>This figure is one of six used to illustrate 'On the Dimensions of the Heavenly Orbs and Spheres, according to the <i>Prutenic Tables</i>, Following the Opinion of Copernicus', appended by Michael Maestlin to Kepler's <i>Mysterium cosmographicum</i>. In this appendix Maestlin provides an exposition of Copernican models for the paths of the Earth, Moon and planets. These models, together with data from Reinhold (in fact, largely from his unpublished <i>Commentary</i> on Copernicus, rather than from his <i>Prutenic Tables</i>), provided the basis for his calculations of the dimensions of the circumsolar spheres. In this diagram AB is the semidiameter of the Earth; BC is the line from the point of sight to the Moon lying on the horizon; AC is the distance of the Moon from the centre of the Earth.</p>