Lowell Observatory's Amazing Anderson Mesa

Posted by David Eicher
on Tuesday, July 25, 2017

A junction of the incredible new Navy Precision Optical Interferometer (NPOI), operated by the U.S. Naval Observatory and Lowell Observatory, at the Anderson Mesa site near Flagstaff, Arizona. Photo by Art Storbo.

In June I had the great fortune to attend my first meeting of the Board of Advisors at Lowell Observatory. This great institution is unique in the astronomy world, as I’ve written before, and should be treasured by all who adore the stars. 

I’ve been here, there, and everywhere since, and finally have my feet back on the ground in Wisconsin for more than a few days. This situation allows me to finally share some photos by a fellow board member, Art Storbo, who sent me these nice images a few weeks ago. 

During part of one day on the Lowell visit I joined a small group including Art and his lovely wife Sharon and Lowell astronomer Gerard van Belle. We headed to Anderson Mesa, some 15 miles southeast of Flagstaff, where Lowell and the U.S. Naval Observatory have facilities. 

I had been out to Anderson Mesa a couple times before — once long ago to observe — to see the 1.8-m Perkins Telescope and the 1.1-m John Hall Telescope. The former originally (1931) stood at Perkins Observatory in Delaware, Ohio, and was moved to Arizona for better skies in 1961. It’s a joint venture of Lowell, Boston University, and Georgia State University. 

The Hall Telescope was installed at Anderson Mesa in 1970. Both telescopes have performed incredible, workhorse duty for all manner of astrophysics projects over the years, and are now considered to be elder statesmen. 

Our main objective stood nearby: the Navy Precision Optical Interferometer (NPOI). This joint project of the U.S. Naval Observatory, the Naval Research Laboratory, and Lowell represents the kind of cutting-edge instrumentation that will revolutionize astronomy. As such, you should definitely be aware of this facility and what’s happening here. Our group was proud to be given a tour of the facility, which is laid out in a triaxial arrangement, by Gerard, as this summer he was announced as Director of NPOI. We were getting a ground tour of the facility from the head man. 

NPOI is an optical interferometer that uses, splayed out on its tracks, multiple telescopes to create the effect of a single, enormously large instrument. The interferometric technique is analogous to that used by the Very Large Array radio telescope, although this one is of course an optical instrument. NPOI is the largest such facility in the world, employing potential telescope separations of up to 432 meters and is the only one specifically for the challenges of visible light work. 

By precisely beaming the light from up to six telescopes through long tubes and reassembling them at very high precision, the facility can produce extraordinary image detail from the resulting data. 

You can read more about NPOI and take an online tour here:


Enjoy! And many thanks to Art Storbo for the great photos used here. 

Lowell astronomer Gerard van Belle at the 1.8-m Perkins Telescope, Anderson Mesa. Photo by Art Storbo.

The dome of the 1.8-m Perkins Telescope at Lowell’s Anderson Mesa. Photo by Art Storbo.

Lowell astronomer Gerard van Belle stands beside the 1.1-m John Hall Telescope at Anderson Mesa. Photo by Art Storbo.

Inside the control room of the 1.1-m John Hall Telescope, Anderson Mesa. Photo by Art Storbo.

The dome of the 1.1-m John Hall Telescope, Anderson Mesa. Photo by Art Storbo.

An overhead Google Earth view of the NPOI Array. Photo by Art Storbo.

A portion of the NPOI contains a siderostat and a “lizardhead” directing the beams into the long tubes for reassembly. Photo by Art Storbo.

Inside one of the stations, Gerard van Belle explains the siderostat operation. Photo by Art Storbo.

Beam equalization tubes are used to make the effective distances between the different telescopes precisely equal for the image reassembly. Photo by Art Storbo.

Gerard van Belle explains the control room at NPOI. Photo by Art Storbo.

A whiteboard in the NPOI control room: interferometry made simple! Photo by Art Storbo.

In a special equipment room, equalized beams enter for reassembly into a single image. Photo by Art Storbo.

Equipment showing elements of the NPOI beam reassembly process. Photo by Art Storbo.

The newest NPOI beam recombination array. Photo by Art Storbo.

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