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| Green Sky Utah Airglow Astrophotography Canon 60Da |
About 60% of the natural brightness of the night sky at zenith is made up of Airglow. Maximum brightest usually appears at about 10-15 degrees above the horizon, because of the greater the depth of atmosphere at this angle. Airglow is not always uniform. Gravity waves may create considerable variation of Airglow brightness.
You can see Airglow only in real dark sky, but naked eye could not recognize colors. Photos with long exposure able get the colors of Airglow.
The usually dominant color of airglow is green originated from molecular oxygen at 90 to 100 km high. Orange and reddish hue caused by atomic oxygen in 150-300 km above the ground, Yellow light comes from sodium atoms in a layer at about 90 km.
