|The Brightest Noctilucent Clouds - Intensely bright and extensive NLCs shone over Europe on the nights of 17/18 and 18/19 June. Their electric bright streaks and whorls were easily visible in the north west not long after sunset. These images are by Martin McKenna (site) of Maghera, Northern Ireland.
"The most spectacular NLC structures I have ever seen in my life. These could be seen moving in real time with the naked eye while casting shadows. The multi-colours, consisting of blue, gold, yellow, green and white, could be seen reflecting off passing tropospheric cloud which was amazing. It was the sight of a lifetime. Images are not 'super processed', just one click of contrast and a very slight unsharp mask."
NLCs are Earth's highest clouds 50-53 miles up in the immensely rarefied upper atmosphere where the pressure is around five millionths of that at sea level. The clouds of tiny ice crystals are a few miles below the mesopause, the atmosphere’s coldest point. The clouds need its exceptionally low temperatures (below –123C) for the crystals to form in the ultra dry conditions. Paradoxically, the mesosphere is at its coldest in summer.