News has just come out this month that Pluto occulted a 15th magnitude star (UCAC2 25823784) in the constellation Sagittarius, with the resulting shadow that crossed over parts of the central U.S. One amateur astronomer in the state of Colorado observed a drop in brightness of about 0.45 magnitude when Pluto blocked the light of the star on March 18, 2007. The duration of the occultation lasted about five minutes.

For more on Pluto's atmosphere and the occultation see ~
http://pluto.jhuapl.edu/science/everything...atmosphere.html