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United States Naval Observatory Flagstaff Station, Arizona
- Art & landmarks
- In Flagstaff, Arizona
- 0.7 mi from Route 66
The Naval Observatory Flagstaff Station, known as NOFS, is the U.S. Navy's dark-sky observatory on a 7,600-foot hill about five miles west of downtown Flagstaff, AZ, roughly 0.7 miles off Route 66. Its 61-inch telescope took the 1978 photographs that revealed Charon, the largest moon of Pluto. Set up in 1955, the station measures star positions with great precision. It is a working military site, open to visitors only on rare tour days.
What it is
NOFS is the dark-sky branch of the U.S. Naval Observatory, which is based in Washington, D.C. Its specialty is astrometry, the exact measuring of where stars and other objects sit in the sky. The star catalogs made here serve Defense Department programs, and together the two sites keep the official celestial reference frame for the Secretary of Defense.
The centerpiece is the 61-inch Kaj Strand Astrometric Reflector, dedicated in 1964 and still the station's main instrument. The hill also holds the 40-inch telescope that started the station, a 1.3-meter telescope built to find faint, cool objects such as brown dwarfs, and smaller automated instruments.
A bit of history
The Navy's 40-inch telescope went into service in Washington in 1934, but the bright city sky kept it from doing its best work. Survey teams tested sites across the West, and a hilltop west of Flagstaff won for its clear, dark skies, easy access and the help of astronomers at nearby Lowell Observatory. The telescope was moved here in late September 1955.
In 1978 Naval Observatory astronomer James Christy, measuring photographs of Pluto made with the 61-inch, noticed a bump on the planet that came and went. It turned out to be a moon, later named Charon. Flagstaff works to keep its night sky dark, and in 2001 it became the world's first International Dark Sky City.
Visiting tips
This is a working Navy facility with no regular visiting hours, not a drop-in attraction, so do not plan to drive up on your own. Staff have offered small guided tours on special occasions, such as during the Flagstaff Festival of Science in September 2025, with reservations required.
For a sure visit, Lowell Observatory, where Pluto itself was discovered in 1930, is about 4.5 miles away and runs public tours and telescope viewing. The Arboretum at Flagstaff is about 1.7 miles from the station, and Braeside Observatory, a small private site, about 0.7 miles.
Practical info
- Address
- 10391 W Naval Observatory Rd, Flagstaff, AZ 86005
- Phone
- +1 928-779-5132
- Website
- nofs.navy.mil
- Hours
- We have no opening hours for this stop yet — check the official site.
- On site & nearby
Sources: OpenStreetMap contributors (ODbL) · Wikidata · official site — may be outdated. Suggest a fix
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Nearby stops
All of Arizona0.7 mi from United States Naval Observatory Flagstaff Station
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Questions
Can you visit the Naval Observatory in Flagstaff?
Only on special occasions. The station is a working Navy facility with no regular visiting hours. It has opened for small guided tours with reservations, for example during the Flagstaff Festival of Science in the fall. Lowell Observatory, about 4.5 miles away, is the place in Flagstaff for everyday public stargazing.
Why is there a Naval Observatory in Flagstaff?
The Navy needed darker skies than Washington, D.C., could offer. After testing sites across the West, it picked a hilltop about five miles west of Flagstaff, at roughly 7,600 feet, for its clear nights and easy access, and moved its 40-inch telescope there in 1955. Flagstaff's strict lighting rules help keep the sky dark.
What was discovered at the Naval Observatory Flagstaff Station?
Charon, the largest moon of Pluto. In 1978 astronomer James Christy found it on photographs of Pluto taken with the station's 61-inch telescope. He named it after his wife Charlene, whose nickname was Char, and the name also belongs to the ferryman of Greek myth. The moon is about half the size of Pluto.
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