Astronomical Images : Table of the equation of days

Georg von Peuerbach

Astronomical Images

<p style='text-align: justify;'>Georg Peuerbach (Georgius Aunpekh) was born in Peuerbach, near Linz. He studied at the University of Vienna, obtaining his BA in 1448 and MA in 1453. He held positions as court astrologer to the king of Hungary, and then to Emperor Frederick III. The <i>Tabulae eclypsium</i>, originally dedicated to Johann Vitez, Bishop of Grosswardein (now Oradea, Hungary), were probably completed around 1459 and is Peuerbach's most impressive work. The tables allow the calculation of the course of the Sun and Moon and therefore the prediction of eclipses. Although they were based on the <i>Alphonsine Tables</i>, they also contain new computations by Peuerbach. This table of 'the equation of days' relates to the correction of days, and indicates the time difference between the true solar day (which is variable) and the mean solar day (which is constant). The solar day is variable because the daily solar velocity is variable and because the correspondence of the degrees on the ecliptic (the path of the Sun) to the degrees on the equator (the basis of time) varies. The left-hand column shows the solar longitude.</p>