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Noctilucent Cloud
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There was a fine display of noctilucent clouds (NLC) in Lund last night. I had heard that there might be a display of northern lights, so I left my Canon EOS 750D outside, pointing northwards and taking 15-sec exposures all night at ISO 200.
You can see the whole video that I recorded on YouTube here: https://www.youtube.com/watch?v=Rwev9hQy_JA
In the event, the northern lights didn't come this far south -- I think they were visible about 100 miles north of here. But as a consolation prize, I picked up a bright display of NLC instead.
NLC are caused by ice crystals forming at 80km altitude - high enough to be illuminated by the Sun even when the ground below is in darkness. They're only seen at high latitudes, and curiously there are no recorded observations of them before 1885, although they are now quite common.
This was my second sighting of NLC since moving to Lund, and once again, I was struck by how bright they were - I could see them out the window without turning the light out. They persisted until eventually fading into dawn twilight.
Comments
Dominic I love the time lapse
Dominic I love the time lapse video; my attempt to do something similar went awfully wrong. It's fascinating to see the changing morphology of the clouds, and see the display widening as Sandra recently described, which is presumably the changing altitude of the Sun rather than changes in the clouds themselves. Really impressive capture.
Technical details
I use a program called gphoto2 to control the timelapse photography. It lets you connect your DSLR to your laptop over USB, and then send commands to the camera to change exposure and take pictures. You do need to be able to do a bit of programming in order to actually automate that into a loop, though. I use a simple python script, and there are some tutorials on how to do this around the web.
As it happens I nearly screwed it up myself -- the Canon 750D is a relatively new model, and gphoto2 doesn't seem to support it very well yet. So about one in every ten exposures didn't work, but that wasn't the end of the world.
Then I imported all the images into Adobe Lightroom to zoom in, and adjust exposure and contrast. From there, the images went into Premiere Pro so I could pan across the frame to follow the most interesting clouds.