Canada - Robert Downie
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Blood Aurora

A rare 'blood' Aurora fills the sky across the Northern Rockies. Red or ‘blood' aurora’s are created by oxygen atoms at an altitude of between 200–500 km (120-300miles) colliding in a high energy state and emitting red light at 630 nm. In contrast the more common green aurora are oxygen atoms at a lower altitude of 70-200km (40-120 miles) and lower energy state emitting light at 557.7 nm. In most cases to see a red aurora you need an extremely dark sky and to be looking from a lower latitude across the top layers of a distant high latitude aurora. When the aurora is closer or overhead, the subtle high altitude red fringe is drowned out by the intensity of the lower altitude green aurora. In this shot the green aurora is also visible spilling over the mountains however it has taken a more yellow hue as it’s mixed with the light of the red aurora from behind it. If you look at the high resolution version of this shot you can see 7 shooting stars in the time it took for this 20 second exposure, although 6 of them are quite faint. The shot was taken at a latitude of 55 North looking across the rugged Hart Ranges of the Northern Rocky Mountains which form part of the Pine Le Moray Provincial Park. British Columbia, Canada


From Astrophotography