Wilhelm Foerster had been appointed a second assistant in 1855 and in 1865 he succeeded Encke as director. He modernised the Observatory, promoted the founding of Potsdam Astrophysical Observatory and founded the Urania Society to promote popular interest in Science.
In 1860, he discovered the asteroid Erato, the 62nd. asteroid to be discovered.
During the DDR-period, he received especial mentions for his anti-Bismarck stance, particularly during the period of the anti-socialist laws at the end of the 19. century. When the First World War broke out, he appealed to the government, along with Einstein, to cease hostilities.