One of the two original photographic plates used in the discovery of Pluto.
One of the two original photographic plates used in the discovery of Pluto. All writting is that of Clyde Tombaugh on the original envelope that contained the plate, now taped to a new storage envelope. The other plate resides at the Smithsonian Institution. Skyscrapers were very fortunate to have this "behind the scenes tour" at historic Lowell Observatory!
Lowell Observatory/Arizona Trip 2005