Nacreous Clouds, Göteborg, Sweden    Imaged by Håkan Pleijel on 19th January 2008 approximately 45 minutes after sunset. The clouds, 9-16 miles high, are still in sunlight and their miniscule ice crystals diffract light to form the iridescent colours. Type II PSCs surround the nacreous clouds. The clouds were seen over large parts of Sweden and southern Norway on this and the following day 1,2.   Image ©Håkan Pleijel, shown with permission.