He married in 1925 and worked for two years in the Bonn Observatory[3] with Küstner, who was involved in the planning of star catalog Astronomische Gesellschaft Katalog 2 of the Northern Hemisphere.

[2] After Adolf Hitler had come to power in 1933, at least 48 colleagues in the science faculty at Göttingen were driven into exile because of their religious, or more rarely political beliefs (Gesetz zur Wiederherstellung des Berufsbeamtentums, 7 April 1933), amongst them Max Born.

[5] In September 1933, the local NSDAP judged Heckmann as "long time member of the leftist wing of the Catholic Zentrumspartei, unreliable and pro-Jewish (judenfreundlich)".

Likewise, in 1934 Walther Gerlach (1889-1979) suggested he come to München, but a Nazi official (Gaudozentenbundsführer Wilhelm Führer) and a member of the Nationalsozialistischer Deutscher Studentenbund turned him down.

In December 1936, he was urged to apply for the position vacated by Erwin Finlay Freundlich at the University of Istanbul, a highly political position serving military interests (observation of the sun’s surface for solar flares resulting in interference with radio communications on Earth), but eventually Hans Oswald Rosenberg was chosen.

[5] Until 1935, Heckmann measured star colors in the red and blue spectrum with photometry with a telescope costing "two years of painstaking adjustment until it began working properly".

[2] In the fall of 1937 the Hamburg University faculty finally called on Heckmann, after having been obstructed for years by the Government of the Reich, and by various agencies within the Nazi Party.

On May 1st, 1937 Heckmann joined the Nazi Party, encouraged by Werner Heisenberg in order to thwart members of Deutsche Physik to occupy teaching positions.