David Origanus · 1609
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David Origanus (David Tost, 1558–1628) taught Greek and mathematics at the Viadrina University in Frankfurt an der Oder. His Ephemerides Brandenburgicae gives the day-by-day positions of the Sun, Moon and planets for the sixty years from 1595 to 1655. The positions of the two great lights are computed twice, on the Tychonic and on the Copernican basis.
The book opens with its dedication to Johann Sigismund, Elector of Brandenburg, and with the imperial and French royal privileges that protected it from piracy. Then comes Origanus’s long introduction, which is a textbook in its own right.
Its first part, On Time, covers calendars and chronology: the old and the Gregorian calendars and the cycle of epacts, a table aligning the kings of Judah and Israel, the length of the day at different latitudes, the equation of time, and a catalogue of places for converting the ephemerides to other parts of the earth. The second part, On Motions, treats the stars, the orbs and the aspects, the motion of the heavens, and how to compute a planet’s true position for any time and place. The ephemerides themselves follow, with their supporting tables.
Ephemerides were the working tools of early modern astronomy, used by astronomers, physicians, calendar-makers and astrologers alike. Setting Tycho’s parameters beside Copernicus’s in a single work let the reader see where the two systems actually diverged in prediction, at a time when that question was still open.
The source is the 1609 Frankfurt an der Oder printing, from the Bavarian State Library.