Two-page autograph letter signed "Clyde W. Tombaugh" on New Mexico State University Department of Astronomy letterhead, 2 July 1991, to John Adams, Toronto: Charon's orbit has been edgewise, allowing "the first reliable measure of its size: diameter of Pluto = 1,420 miles... Charon = 750 miles"; Pluto's light "is very faint, = 1 candle at a distance of 200 miles"; scanning "many pairs of 14x17 inch plates thru a microscope eyepiece... is brutally tedious"; and on finding a possible tenth planet he refers to his article in Sky and Telescope, April 1991. A superb scientific letter from the discoverer of Pluto. Condition: clean.
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