The 13-inch Astrograph built for the search for Pluto, that Clyde Tombaugh used to find the “new planet” in 1930. Tombaugh used this instrument, now an historic site at the Lowell Observatory, to take images of the sky on glass plates which he developed in the darkroom one floor below. He used the blink comparator to compare plates take on different nights to look for objects that moved.
The Amazing Sky 