As in our opening study “Astronomen, Akten und Affären” on the history of the Astrophysical Observatory Potsdam, all quotations from the holdings of the Brandenburg State Main Archive, the Archive of the Berlin-Brandenburg Academy, the Archive of the Prussian Cultural Heritage Foundation, and the Federal Commissioner for the Records of the State Security Service of the former GDR are italicized. These quotations are either available to the author as files or are taken from the book “Versagtes Vertrauen. Wissenschaftler der DDR im Visier der Staatssicherheit” by R. Buthmann, as indicated. Photographs were taken by the author or are in the public domain (gemeinfrei).