Simplify the following text for a Grade 10 native English-speaking person.
Original: Charon was discovered by astronomer James Christy on June 22 , 1978 , when he was examining highly magnified images of Pluto on photographic plates taken a couple of months earlier .
Simplified: Charon was found by astronomer James Christy on June 22 , 1978 , when he was looking at highly blown up picture of Pluto on a photographic plate that taken a couple of months before .