which I've covered before, is of airglow, fainter, but generally more visible from anywhere on the Earth's surface. Shown at left is the view from the International Space Station, with airglow seen as a diffuse greenish glow in the atmosphere. An excellent discussion of various properties of airglow is presented in the archives of Atmospheric Optics and Optics Picture of the Day, maintained by Les Cowley.
discovered by Aden Meinel in the 1950s, a well known astronomer of the middle of the last century that all Arizonans likely know (and I had occasion to meet several times). Fortunately, I brought my IR-modified Canon 20D, which captures near-IR redward of 720nm. At left is shown a fisheye view showing this OH emission - it looks like clouds, but the sky is just aglow from a multitude of emission lines. There was no moonlight, no city lights to illuminate these "clouds" from below... Looking North towards Polaris, just above center, the fisheye view shows the Big Dipper at left to Cassiopeia at right.
So here are the full-size frames from the fisheye
view in visible light at left, and at right is a frame from an 80mm lens shooting across the Canyon to the North Rim Lodge and stars and airglow to the horizon. Certainly if there were clouds (as it appears in the IR view above, but it was perfectly clear), there would be obscuration of the rising stars. You can also see from these images that the airglow is not uniform in intensity nor static. "Gravity Waves" propagate from the lower atmosphere, affecting the density and chemical abundance, changing the appearance of the airglow pattern.
And while single frames are of interest, many frames taken over time show the change in airglow illumination. While I didn't invest a lot of time in taking frames (a cold wife, waiting in the car tends to shorten the imaging session), taking frames over a 15 minute period, and cycled several times will have to do for now... Enjoy the view, and keep looking up!
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