This is an auroral (Northern Lights) display which occured sometime in the early nineties. The image was taken from Central Illinois (about 40deg. N latitude), and the extent of the display was well overhead, even in the light of the full moon. Needless to say, it is one of the most intense aurora I have ever seen. If you have never seen this phenomenon, I highly suggest trying to do so when the opportunity arises. Photos simply can't convey the full impact of what is happening. The curtains are contantly moving, sometimes jarringly so, and the colors change from moment to moment.

I did not record the exposure times, but I believe they were less than 5 minutes as the stars do not have trails. The lens used was a standard 50mm lens with a screw-on type of fisheye converter which gave an almost 180 degree field of view. This is why the horizon looks curved in the photos. The odd rings in the center are an artifact of the less-than-precise optics of this converter.