He did his Ph.D.dissertation in 1918 at the Landessternwarte Heidelberg-Königstuhl (Königstuhl Observatory, near Heidelberg) at the University of Heidelberg[1] (http://www.lsw.uni-heidelberg.de/personnel/diss.phtml).
At the time, the observatory at Heidelberg was a center for asteroid discovery under the direction of Max Wolf. During his time there, Ernst discovered one asteroid.