It was a great night for shooting meteors as the annual Perseids put on a show.
For the Perseid meteor shower I went to one of the darkest sites in Canada, Grasslands National Park in southern Saskatchewan, a dark sky preserve and home to several rare species requiring dark nights to flourish – similar to astronomers!
This year a boost in activity was predicted and the predictions seemed to hold true. The lead image records 33 meteors in a series of stacked 30-second exposures taken over an hour.
It shows only one area of sky, looking east toward the radiant point in the constellation Perseus – thus the name of the shower.
Extrapolating the count to the whole sky, I think it’s safe to say there would have been 100 or more meteors an hour zipping about, not bad for my latitude of 49° North.
The early part of the evening was lit by moonlight, which lent itself to some nice nightscapes scenes but fewer meteors.
But once the Moon set and the sky darkened the show really began. Competing with the meteors was some dim aurora, but also the brightest display of airglow I have even seen.
It was bright enough to be visible to the eye as grey bands, unusual. Airglow is normally sub-visual.
But the camera revealed the airglow bands as green, red, and yellow, from fluorescing oxygen and sodium atoms. The bands slowly rippled across the sky from south to north.
Airglow is something you can see only from dark sites. It is one of the wonders of the night sky, that can make a dark sky not dark!
The lead image is stack of 31 frames containing meteors (two frames had 2 meteors), shot from 1:13 am to 2:08 a.m. CST, so over 55 minutes. The camera was not tracking the sky but was on a fixed tripod. I choose one frame with the best visibility of the airglow as the base layer. For every other meteor layer, I used Free Transform to rotate each frame around a point far off frame at upper left, close to where the celestial pole would be and then nudged each frame to bring the stars into close alignment with the base layer, especially near the meteor being layered in.
This placed each meteor in its correct position in the sky in relation to the stars, essential for showing the effect of the radiant point accurately.
Each layer above the base sky layer is masked to show just the meteor and is blended with Lighten mode. If I had not manually aligned the sky for each frame, the meteors would have ended up positioned where they appeared in relation to the ground but the radiant point would have been smeared — the meteors would have been in the wrong place.
Unfortunately, it’s what I see in a lot of composited meteor shower shots.
It would have been much easier if I had had this camera on a tracker so all frames would have been aligned coming out of the camera. But the other camera was on the tracker! It took the other composite image, the one looking north.
The ground is a mean combined stack of 4 frames to smooth noise in the ground. Each frame is 30 seconds at f/2 with the wonderful Sigma 20mm Art lens and Nikon D750 at ISO 5000. The waxing Moon had set by the time this sequence started, leaving the sky dark and the airglow much more visible.
— Alan, August 13, 2016 / © 2016 Alan Dyer / AmazingSky.com