In the location's words:

The Wilhelm Foerster Observatory in Berlin-Schöneberg is also open during the closing time of the Planetarium am Insulaner . At the "Observation night at the Wilhelm Foerster Observatory" you can expect an exciting guided tour and guided observation with the impressive "Bamberg refractor". There is also the opportunity to explore the Berlin night sky yourself through smaller telescopes on the roof. The "observation night" takes place on Fridays and Saturdays from 9 p.m. to midnight, and you can join in at any time during the three hours.

Das Planetarium am Insulaner und die Wilhelm-Foerster-Sternwarte sind ausschließlich zu den Veranstaltungen geöffnet. Die Kasse im Planetarium öffnet eine Stunde vor Veranstaltungsbeginn, die der Sternwarte kurz vor den Führungen.