Noctilucent Clouds Over Southern Sweden

October 16, 2014

Noctilucent Clouds Over Southern Sweden

Photographer: Ina Rendtel
Summary Author: Ina Rendtel; Jim Foster
 
Shown above are bluish-white noctilucent clouds (NLC) as observed over Ekstakusten, Gotland, Sweden, just before midnight on July 18, 2004. After sunset at this time of year in Scandinavia, the Sun is never far below the horizon (not more than about 16 degrees) and thus the night sky is never truly dark. Since NLCs occur so high in the atmosphere (approximately 50 mi or 80 km) they can reflect sunlight hours after local sunset -- or before sunrise. They form when water vapor condenses about minute particles in the mesosphere, possibly meteoric in origin.
 
Photo details: Camera Model: Canon EOS 400D DIGITAL; Focal Length: 32.0mm; Aperture: f/4.0; Exposure Time: 4.000 s; ISO equiv: 800. Taken at 11:47 p.m.