Barring the common late afternoon thunderstorms of June, Coloradans will get a rare chance to see the moon slide across the face of the sun during a partial solar eclipse on June 10. Solar eclipses usually occur twice a year, but are not always visible from the United States, according to experts at Fiske Planetarium and Sommers-Bausch Observatory at the University of Colorado at Boulder. In fact, the next chance to see a solar eclipse in Colorado won't be until May 20, 2012, according to Robert Stoller, operations manager at Fiske Planetarium.