Noctilucent (“night-shining”) clouds are a rare phenomenon: the highest clouds in the atmosphere, at altitudes between 47-53 miles, consisting of tiny crystals of water ice about 100nm in diameter and requiring very cold temperatures to form. Not fully understood, they are a recently discovered meterological phenomenon with no record of their observation before 1885.
They also make a beautiful display of pale bright fibrous blue against the cobalt velvet of night…
Two views, part of a stitched panorama.