Clyde here at least gets equal billing with Percival Lowell. Notice that in June 1930 astronomers are still puzzling out Pluto’s size. They’re getting closer — rather than being 1200 times the size of Earth, now it’s “judged to be the same size as earth.”  (Today we know its mean radius to be 0.18 of Earth.)  Estimates of Pluto’s size decreased over the course of the 20th century; in 1976, astronomers determined that Pluto’s surface featured methane ice, which meant that the planet’s albedo was higher than had been theretofore suspected — which, in turn, meant the planet was smaller than it appeared.

The discovery of Pluto’s moon, Charon, in 1978, allowed for very accurate measurements of Pluto’s mass — now determined to be about 0.2% of Earth’s.

Here’s the larger version of that iconic picture of Lowell at his 24″ Clark.  Notice the handsome chair.  As his descendents say, “Percy brought a lot of Yankee with him to Flagstaff.”

If you visit Lowell Observatory you can see this telescope still in operation — in fact, you can look through it!  Check out Lowell’s visiting hours and directions here.