Lowell Observatory

Percival Lowell founded the observatory in 1894, largely to study Mars, whose surface he was convinced carried artificial canals - he was wrong about that, but the institution he built did serious work. Vesto Slipher measured the redshifts of spiral nebulae here from 1912, providing the observational basis Hubble later used to establish that the universe is expanding. Clyde Tombaugh, a farm boy hired to blink photographic plates, found Pluto in February 1930 by comparing images taken days apart; the telescope he used is preserved. Flagstaff became the world's first International Dark Sky City in 2001 with lighting ordinances protecting the observatory. Public evening programmes run telescopes for visitors.

What you actually see

• The telescope that found Pluto - preserved with the blink comparator work.
• Slipher's redshift measurements - the basis for cosmic expansion.
• Lowell's Mars canal obsession - which the observatory explains honestly.
• The first Dark Sky City - Flagstaff's lighting rules protect the site.

When to go

Year round; evening programmes are the point. An evening.

Honest expectations

Cloud cancels telescope viewing with no refund on some tickets. Flagstaff is at 2,100 metres and evenings are cold in any season. Programmes book out. The Mars canals were an error, and the site says so.

Nearby

The Grand Canyon is about ninety minutes north; Sunset Crater is north-east.