Observatorio Naval de los Estados Unidos
Charon was discovered by United States Naval Observatory astronomer James Christy, using the telescope at United States Naval Observatory Flagstaff Station (NOFS). On June 22, 1978, he had been examining highly magnified images of Pluto on photographic plates taken with the telescope two months prior. Christy noticed that a slight elongation appeared periodically. The bulge was confirmed on plates dating back to April 29, 1965. The International Astronomical Union formally announced Christy's discovery to the world on July 7, 1978.