In this short video I present real-time and time-lapse sequences of noctilucent clouds (aka NLCs or polar mesospheric clouds, PMCs) photographed from southern Alberta on June 4/5, 2019.
It demonstrates the amount of motion these high-altitude clouds typically exhibit, usually in an east-to-west direction across the north.
NLCs are water vapour clouds at roughly 80 km altitude, above the stratosphere and at the edge of space. Their origin is still a bit of a mystery. They are visible only in summer around solstice and only from mid-latitudes of about 50° to 60° North. They are visible at night (thus "nocti - lucent") because they are illuminated by sunlight streaming over the pole.
The video includes real-time video shot at 24 frames per second showing that, unlike auroras, NLCs show little motion to the eye. It takes the time-lapse clip shot over 30 minutes to show their characteristic east-to-west motion, and the "standing wave" pattern of the clouds. It also shows the clouds dimming as the Sun angle drops lower below the horizon and the illumination of the clouds decreases.
The real-time video was shot with a 135mm telephoto lens in 4K at 24 fps and with a 1/8-second shutter speed at ISO 6400, then processed in Photoshop to brighten the scene.
The time-lapse was from 540 frames, each 2-second exposures at 1-second intervals at ISO 1600. Both sequences were shot with the Sony a7III camera. I processed and rendered the time-lapse frames using LRTimelapse 5.2.
I started the time-lapse sequence after shooting the real-time video.
Music is "Lonely Nights" by Adi Goldstein, used with permission.
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