Rocket exhaust cloud "over" Kuopio, Finland, in July 1987. This exhaust cloud was left by a Soviet rocket, launched from the Kola peninsula. In this photo, the cloud is already quite spread over, but very colourful. The colours actually revealed that these were not noctilucent clouds, and the structures are quite unusual too. This photo was taken during a noctilucent cloud watch, around midnight.

(© Timo Nousiainen)