Volkssternwarte Köln

In the page's words:

100 years ago, a few enthusiasts founded the "Association
of the Friends of the Stars of Cologne". The first observatory was later built at
the school on the Großer Griechenmarkt. For 50 years our
observatory - home of the CLT (Cologne Large Telescope),
the largest publicly accessible telescope in NRW - in Cologne-Sülz.
in Cologne-Sülz. The observatory offers regular lectures,
observations and astronomy courses for young and old. And
And if you want to be more than just a visitor, but perhaps also actively
actively involved, is very welcome as a member.