This Saturday members of the Ryerson Astronomical Society visited Yerkes Observatory to use the 41-inch reflector. Luckily the clouds cleared for observing until midnight or so, when the clouds reappeared. While taking a break, I noticed a faint glow low to the north, and assumed it was scattered light from the setting first quarter moon, but then I realized the moon was too far to the west for that to happen. Then the glow turned green, and I knew we had an aurora. The clouds cleared out, and we were treated to a fantastic display of the northern lights. It started out green and in the north, and spread overhead, where it suddenly changed color and we saw light pastel blue and violets in addition to the green. The display continued until dawn at 4AM.