It’s noctilucent cloud season again, and last night was a stunning display. Image taken looking North East at 01:30am.

Noctilucent clouds are the highest clouds in Earth’s atmosphere, located in the mesosphere at altitudes of around 76 to 85 km (200,000ft). They are too faint to be seen in daylight, and are visible only when illuminated by sunlight from below the horizon while the lower layers of the atmosphere are in Earth’s shadow.

Noctilucent clouds are produced by tiny water ice crystals (up to 100nm in size) reflecting sunlight while the sun is below the observers horizon. All of the noctilucent clouds I have witnesed over the past few years have been pale blue in colour, (other colours including red and green occur can also occur).  The characteristic blue colour comes from absorption by ozone in the path of the sunlight illuminating the noctilucent cloud.

Looking forward to more displays over the next few days.

Steve