This is a 10 hour long exposure during a pitch black night.
Shot on some Fuji 4x5 slide film, cross processed.

^{There is a great aspect about film photograohy when doing long exposure: Due to the reciprocity effect there is no big difference between 1h and 10h exposure; so I can just leave the camera there and go to sleep (but have to wake up before it gets light!).}