1616/1617, Scheiner worked as a successor to Father Johannes Lantz S.J. in Ingolstadt, teaching mathematics (physics and astronomy) and Hebrew. He lectured on sun dials, practical geometry, astronomy, optics, and the telescope.

In 1611, Scheiner observed sunspots; in 1612 he published the "Apelles letters" in Augsburg. Mark Welser had the first three Apelles letters printed in Augsburg on 5 January 1612. They provided one of many reasons for the subsequent unpleasant