Circumpolar star trails at dawn over the historic Butala homestead at the Old Man on His Back Prairie and Heritage Conservation Area in southwest Saskatchewan, taken May 2015. This is a stack of 70 frames from a larger time-lapse sequence, from the start of the sequence in the dusk twilight, with some aurora active and adding green and magenta to the sky. Cassiopeia is at left over the house. <br /> <br /> Each exposure is 40 seconds with the 14mm lens at f/2.8 and Canon 60Da at ISO 1600. Stacked with Advanced Stacker Actions, Comet effect. The foreground comes from a stack of 8 of the first exposures, mean combined, to smooth noise.