U.S. Naval Observatory at Flagstaff

The U.S. Naval Observatory began in Washington, D.C, but that site is no longer used for research because of fog and light pollution. The Flagstaff Station was created as the Naval Observatory's Research & Development arm. Not all of the observatory's research is for the Navy; work is also done for star catalogs, GPS, and other programs. The facility's specialties are instrument design, innovative programs, and detector development, design and testing.

I visited the USNO Flagstaff Station, located 5 miles west of Flagstaff, Arizona, on May 10, 2003 on a tour conducted by special arrangement for members of the East Valley Astronomy Club. On our tour we saw the Station's 4 major instruments. (The USNO has a 2nd facility in the Flagstaff area, an optical interferometer at Anderson Mesa 15 miles southeast of Flagstaff, but that facility was not included on this tour).


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The U.S. Naval Observatory Flagstaff Station has a terrific view of the San Francisco Peaks.


0.2 meter Transit Telescope (FASTT)

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Our tour group in the building that houses the transit telescope.


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The 0.2 meter Transit Telescope rotates in elevation only. It is completely automated, and uses CCD's to measure the position of hundreds of thousands of stars fainter than 17th magnitude. Focal ratio f/10.4.


1.0 meter (40 inch) Ritchey-Chretien Telescope.

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This is the dome for the largest and last Ritchey-Chretien telescope designed and built by George W. Ritchey. Completed in 1934 and originally located in Washington D.C., it was moved here in 1955. It is the oldest telescope at the USNO Flagstaff facility.


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The Ritchey-Chretien Telescope is being retrofitted with adaptive optics. It is used to get accurate measurements of minor solar system bodies, and may be used to get better orbits for Phobos & Diemos, the moons of Mars. Overall focal ratio f/7.3. Note the vintage Clarke refractor used for a finder scope.


1.3 meter Telescope

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The 1.3 meter is the facility's newest telescope, having been completed in 1999.


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A modified Ritchey-Chretien design, the 1.3 meter is completely automatic. It now uses a single CCD, but will be retrofitted with a CCD array. Overall focal ratio f/4.


1.55 meter (61 inch) Telescope

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The 1.55 meter is the facility's largest telescope. The dome is doubly walled, the 1 foot gap filled with crushed aluminum, which keeps the interior at the nighttime temperature. The station's office building is on the right.


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Installed in 1963, the 1.55 meter is a modified Cassegrain f/9.8 with a flat secondary mirror. It was designed and built by Kaj Strand, Scientific Director of USNO at the time. The mount's sturdy construction (total weight including the mount is 36 tons) is critical for its extremely accurate measurment of stellar parallax. It is also used as a test bed for near-infrared detectors.


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The control room for the 1.55 meter telescope. Dr. Alice B. Monet is on the left; her work is on detecting satellites of asteroids. EVAC Events Coordinator Howard Israel on the right. Thanks to Alice for acting as our tour guide, and thanks to Howard for arranging this tour and the other recent tours for the club.


All photos taken using Kodak Elite Chrome 400 slide film with Olympus OM-1 35mm camera, scanned with Nikon Coolscan LS-2000.

Tours of the observatory are by advance arrangement only; more information may be found at the U.S. Naval Observatory Flagstaff Station web page.


Revised: September 13, 2007
Copyright © 2004 Joe Orman
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