Calling All Amateur Astronomers: Help Solve a Mystery

"For nearly 200 years, astronomers have been wondering why the star epsilon Aurigae turns down its light once every 27 years. Based on careful observations of the star’s periodic dimming, scientists believe that the supergiant star must have a mysterious companion that blocks its light periodically. But they still don’t know what that companion is."

http://www.wired.com/wiredscience/2009/08/citizensky/