Auroras in Nebraska are rare, but who needs auroras when you've got iridescence? University of Nebraska freshman Evan Ludes took this picture of cloud-colors over Omaha on the morning of Nov. 10th:

Colored Skies
© Evan LudesImage Taken: Nov. 10, 2011
Location: Omaha, Nebraska
"I walked out of class this morning and was greeted by one of the best iridescence displays I've ever seen!" says Ludes. "The colors formed on the leading edge of a long stretch of cirrocumulus clouds."

Iridescent colors appear when sunlight shines through water droplets in the edges of clouds. The mechanism is diffraction. The colors are at their brightest and most distinct when the droplets are small and uniformly-sized.

"I'm no optics expert," says Ludes, "but I'm guessing the colors were particularly vivid since these clouds were newly formed and therefore likely had water droplets of similar shape and size. It was incredible how distinct the bands of colors were even when zoomed in at 300mm!"

More images from Evan Ludes here.