Lowell Observatory

Percival Lowell, a Boston astronomer who hoped to find life on Mars, founded this observatory in 1894 on Mars Hill, a mesa about a mile west of downtown Flagstaff at 7,250 feet. He chose Flagstaff for its altitude, dark skies and railroad, and he spent years drawing what he believed were canals on Mars. The discoveries that made Lowell famous came from other questions. In 1912 V.M. Slipher measured the redshifts of spiral galaxies, the first evidence that the universe is expanding. In February 1930 Clyde Tombaugh, hired to run a new 13-inch astrograph in the search for a "Planet X", found Pluto on its photographic plates. In the 1960s the observatory's Clark Telescope was used to make detailed Moon maps for the Apollo missions. The observatory became a National Historic Landmark in 1965.

A visit is part museum, part working observatory. General admission covers the whole day, with re-entry, and includes guided tours, more than 150 exhibits, theater shows and evening stargazing. The centrepiece is the 24-inch Clark refractor, built by Alvan Clark & Sons in 1896, which is still used for public viewing from dusk to 9:30 p.m., weather permitting. Percival Lowell died in 1916 and is entombed in a mausoleum near it. The Rotunda, finished in 1916, houses a museum with his first telescope and the blink comparator Tombaugh used to spot Pluto, and its basement vault keeps the original Pluto discovery plates. The astrograph itself is in the Pluto Discovery Dome. The Giovale Open Deck Observatory has six telescopes for public use, with filtered solar viewing by day. The Astronomy Discovery Center, opened in November 2024, adds a children's exhibit hall, an astronomy gallery, a theater and a rooftop open-air planetarium with heated seats.

Telescope viewing usually starts around sunset, which can be as early as 4:30 p.m. in winter and as late as 8 p.m. in summer. Mars Hill is high and cold after dark, so dress in layers, and expect some walking on slopes. Lowell says the average stay is about two hours. Pets are not allowed on campus, only service animals, and there is no overnight parking. The observatory also started Flagstaff's dark-sky campaign: in 1958 it asked the city to limit searchlights, which led to what Lowell calls the first lighting ordinance designed to protect dark skies, and in 2001 Flagstaff became the world's first International Dark Sky City.