American astronomer (1906–1997) best known for discovering Pluto in 1930. ALS, one page, 5 x 3.5, September 17, 1992. Letter to an admirer. In part: “If there are more planets beyond Pluto, they would have to be 2 magnitudes fainter than my plate limit. I made a thorough search over 2/3 of the entire sky in 14 years, scanned 90 million star images, detected by a 3 1/2 mm shift in 6 days.” In fine condition. RR Auction COA.
