All photographs copyright (2003-2013) by Kris H. Light

This is the comparison scope that Clyde Thombaugh used at the Lowell Observatory to discover Pluto. The observatory is located on top of a large hill in Flagstaff. This instrument let astronomers look at two photos taken on  different nights and compar...
This is the comparison scope that Clyde Thombaugh used at the Lowell Observatory to discover Pluto. The observatory is located on top of a large hill in Flagstaff. This instrument let astronomers look at two photos taken on different nights and compare them. The stars didn't move, but Pluto did.

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