The Sternwarte Düsseldorf (a.k.a. Sternwarte Bilk, Sternwarte Charlottenruhe; Bilk Observatory or Düsseldorf-Bilk Observatory in English) in Düsseldorf-Bilk was a private observatory founded in 1843 by Johann Friedrich Benzenberg. The observatory's main feature was a refracting telescope with 1800mm focal length. After Benzenberg's death the observatory was bequeathed to the city of Düsseldorf.