Noctilucent Clouds

This is my first sighting of these clouds which occur during June in the northern hemisphere. They appear about 60-90 minutes after sunset or before sunrise, low down on a broadly northern horizon.
Tonight they reached a relatively high altitude. They form when water vapour freezes around meteoroid dust at a height of around 85 kms (55 miles) and are illuminated by the Sun which is well below the horizon.
They glow with a strange electric blue colour and are unmistakable. Sadly they are also unpredictable and do not form every night. Still worth looking for if it's clear.
This shot was taken at 11.15pm.