Northern Lights over North Norway, September 2007.
Airglow, or nightglow. Airglow is caused by various processes in the upper atmosphere, such as the recombination of ions which were photoionized by the sun during the day, luminescence caused by cosmic rays striking the upper atmosphere, and chemiluminescence caused mainly by oxygen and nitrogen reacting with hydroxyl ions at heights of a few hundred kilometers. It is not noticeable during the daytime because of the scattered light from the Sun.
 
Even at the best ground-based observatories, airglow limits the sensitivity of telescopes at visible wavelengths. Partly for this reason, space-based telescopes such as the Hubble Space Telescope can observe much fainter objects than current ground-based telescopes at visible wavelengths.
 
The airglow at night may be bright enough to be noticed by an observer, and is generally bluish in color. Although airglow emission is fairly uniform across the atmosphere, to an observer on the ground it appears brightest at about 10 degrees above the horizon, because the lower one looks the greater the depth of atmosphere one is looking through. Very low down, however, atmospheric extinction reduces the apparent brightness of the airglow.
 
One airglow mechanism is when an atom of nitrogen combines with an atom of oxygen to form a molecule of nitric oxide (NO). In the process a photon is emitted. This photon may have any of several different wavelengths characteristic of nitric oxide molecules. The free atoms are available for this process because molecules of nitrogen (N2) and oxygen (O2) are dissociated by solar energy in the upper reaches of the atmosphere, and may encounter each other to form NO. Other species that can create air glow in the atmosphere are hydroxyl (OH) [1] [2] ,[3] molecular oxygen (O), sodium (Na) and lithium (Li).[4] See Sodium layer.
 
The sky brightness is typically quoted in units of astronomical magnitudes per square arcsecond of sky.
Northern Lights in WIsconsin taken on the night of 4/02/11.
Taken witha Canon 40D modified for astrophotography.
Lens used wa a Zenitar 16mm fisheye, and the exposure was 30secs @F/4 @1600ISO
I took this picture of "Airglow" in Beecher Wisconsin on the early morning of July 20th 2012. This was by far the most intense display of this phenomena that I have witnessed so far. Sometimes airglow, or "nightglow can be confused with aurora depending on the intensity. 
If you are in a dark location, and you think you might be seeing airglow, snap a long shot and see what transpires!

Photo info:
Camera: Canon 40D
ISO 1600
Lens Peleng 8mm @ F/4.5
Exposure: 3 mins
Information taken from wikipedia

Airglow, or nightglow. Airglow is caused by various processes in the upper atmosphere, such as the recombination of ions which were photoionized by the sun during the day, luminescence caused by cosmic rays striking the upper atmosphere, and chemiluminescence caused mainly by oxygen and nitrogen reacting with hydroxyl ions at heights of a few hundred kilometers. It is not noticeable during the daytime because of the scattered light from the Sun.

 Even at the best ground-based observatories, airglow limits the sensitivity of telescopes at visible wavelengths. Partly for this reason, space-based telescopes such as the Hubble Space Telescope can observe much fainter objects than current ground-based telescopes at visible wavelengths.

 The airglow at night may be bright enough to be noticed by an observer, and is generally bluish in color. Although airglow emission is fairly uniform across the atmosphere, to an observer on the ground it appears brightest at about 10 degrees above the horizon, because the lower one looks the greater the depth of atmosphere one is looking through. Very low down, however, atmospheric extinction reduces the apparent brightness of the airglow.

 One airglow mechanism is when an atom of nitrogen combines with an atom of oxygen to form a molecule of nitric oxide (NO). In the process a photon is emitted. This photon may have any of several different wavelengths characteristic of nitric oxide molecules. The free atoms are available for this process because molecules of nitrogen (N2) and oxygen (O2) are dissociated by solar energy in the upper reaches of the atmosphere, and may encounter each other to form NO. Other species that can create air glow in the atmosphere are hydroxyl (OH) [1] [2] ,[3] molecular oxygen (O), sodium (Na) and lithium (Li).[4] See Sodium layer.

 The sky brightness is typically quoted in units of astronomical magnitudes per square arcsecond of sky.
Aurora timelapse 4/12/12
Northern Lights over North Norway, September 2007.
Northern Lights over North Norway, September 2007.
Northern Lights over North Norway, September 2007.
See photo in original gallery.

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