Astronomical Images : How to find the true centre and true motion of a superior planet
Georg von Peuerbach
Astronomical Images
<p style='text-align: justify;'>These two diagrams were introduced in the commentary on Peuerbach's <i>Theoricae novae planetarum</i> by Francescus Capuanus, which explains the details of the calculation of the planetary motions. According to the definitions in Gregor Reisch's <i>Margarita philosophica</i> (1503, o2v), the 'true motion' of a superior planet is the arc of the ecliptic between Aries and the intersection with the 'line of the true motion', that is, the line joining the centre of the World and the centre of the planet's body; and the 'true centre' of the planet is the arc of the ecliptic between the 'line of the true motion' and the '<i>linea augis</i>' (the line passing by the centre of the World, the centre of the deferent circle, and the apogee and perigee of the deferent circle).</p>