NLC's are are Earth's highest clouds and occur in altitudes of about 80 km to 85 km. These clouds consists in tiny ice crystals of up to 100nm. NLC's are too faint to be seen in daylight and they are only visible if the sun is between 6° and 16° below horizon. Then the NLC's are illuminated by sunlight while lower layer of the atmosphere are in shadow and sky becomes dark.
The moving filaments that can be seen in the video are caused by gravity waves, the same type of waves which occur if you drop a stone into a pool af water.
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|Date:||Jun 17, 2019 between 22:10 and 23:42 CEST (=UTC+2h)|
|Instrument:||Sky surveillance camera pointing to north|