Fires, Lasers, Squirrels, and Telescopes: A Tour of the Large Binocular Telescope on Mt. Graham, Arizona

Story first featured on the University of Arizona Steward Observatory’s education program “Active Galactic Videos” here

In June of 2004, the Nuttal Fire began along the southern rims of the Pinaleño Mountains in southern Arizona, sparked in two separate locations by lightning strikes. Over the course of a month, the fire burned nearly 30,000 acres and cost over $8 billion dollars.


The mountain views at LBT (Source: Active Galactic Videos)


“A pair of wildfires in southeastern Arizona skirted the Mount Graham International Observatory earlier this month,” wrote Science Magazine. “The telescopes escaped unscathed, but scientists fear that the endangered red squirrels living on the mountain were not as fortunate.”

Both the Mount Graham red squirrel and the Mount Graham International Observatory have been in danger of deadly fires. More recent fires in 2012 and 2016 have threatened the squirrels and observatory, but the observatory has so far fared better than the squirrels. Squirrel populations continue to fluctuate while the observatory operates uninterrupted and advances astronomical knowledge.

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Close-up of the LBT (Source: Active Galactic Videos)

Construction of the Mount Graham International Observatory began in 1989 as a joint program with the University of Arizona, U.S. Forest Service, U.S. Fish and Wildlife Service, and Arizona Game and Fish Department. While the telescopes would have use of the ridges of the mountain, wildlife researchers would have the rest of the mountain to use for the protection of the red squirrel.

Since construction began on Mount Graham, three main telescopes have been housed in the observatory. The first instruments engineered were the Vatican Advanced Technology Telescope and the Heinrich Hertz Submillimeter Telescope, which began operations in 1993 and both are still in operation today. But the most prized possession of the observatory is the Large Binocular Telescope (LBT), which began operations in 2004.

The Large Binocular Telescope is composed of two identical 8.4 meter telescopes, like a binocular. The purpose of having two telescopes is that the two sides increase the light collecting area as well as the spatial resolution . This means that the telescope is able to collect more light from distant objects and examine details that are too small or too close together for other telescopes to tell apart.

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Close-up of the LBT (Source: Active Galactic Videos)

Along with the telescope itself, the LBT utilizes other technologies to observe the cosmos.

“Also attached to the telescope are several different objects to help observing, one of which is the DIMM (Differential Image Motion Monitor),” Barry Rothberg said. “It is basically a small telescope with two apertures, and it compares the motion of the stars in the two apertures, and from that we are able to tell just how steady the atmosphere is.”

For non-astronomers, an aperture is an opening in the lens or mirror of a telescope where light is allowed to enter. The data from the mini DIMM telescope is used to measure how much Earth’s atmosphere might affect the telescope’s observations and what instruments would be best for observing, which is important in calculating the motions of the stars.



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ARGOS in action. (Source: LBTO News)

Barry Rothberg is a support astronomer at the LBT. His main tasks at the observatory consist of preparing astronomers for their observing programs and providing technical, in-person night support during their observation times with the telescope. When not assisting other astronomers, Rothberg conducts his own astronomical research observing asteroids, planets, and other more recently discovered objects such as galaxy mergers and active galactic nuclei.

“We also have a laser guide star system, which we call ARGOS,” Rothberg said. “It is a ground laser optics system. It’s six green lasers which create artificial stars in the sky.”

The purpose of the lasers is to simulate the motions of the stars with the light that comes from the lasers when they are shot into the sky.

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A piece of machinery that rotates the dome of the LBT (Source: Active Galactic Videos)


In order for the LBT to view astronomical objects, a giant dome that encompasses the telescope must rotate 360-degrees so that a rectangular slit opened for viewings can point to different locations in the sky.

“The building rotates on an outer pier, the telescope rotates on an inner pier,” Michael Wagner said. “We can reconfigure the telescope within 20 minutes or less, depending on the configuration. It really gives us an advantage in the astronomy world over other telescopes… which may take much more manpower.”

Michael Wagner is an assistant observatory manager at the LBT. As assistant observatory manager, Wagner plans and supervises many of the activities, maintenance, engineering, and safety procedures at the LBT.

Since it first began operations in 2004, the LBT has continued to expand and challenge modern technology and capabilities.

“LINC NIRVANA is our newest instrument,” Rothberg said. “It is an infrared imager that uses multi-conjugate adaptive optics to help clear the sky up. So very simply, it works [with] lots of little detectors looking at little stars and measuring how the stars move around.”

A person standing next to the LBT for size (Source: Active Galactic Videos)

Adaptive optics compensates for atmospheric turbulence and movement, which may cause an image to distort or become unclear. LINC-NIRVANA and its’ multi-conjugate adaptive optic systems at LBT allows images to be corrected over a larger field of view than older adaptive optics systems.

UA astronomers and LBT staffers alike pride themselves on the premier technologies of the observatory.

According to the website of the Large Binocular Telescope Observatory (LBTO), “LBTO has a dual mission: (1) to be the first Extremely Large Telescope (ELT), experimenting with new technologies that will be used for the ELT generation now currently under construction by enabling 23m-aperture class science and (2) to be one of the leading 8-m class telescopes.”

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Outside the LBT (Source: Active Galactic Videos)

The LBT is the first of the Extremely Large Telescopes, which is an elite group of telescopes. These telescopes challenge new technologies in order to look deeper into space; many of these telescopes can produce higher resolution images than the Hubble Space Telescope. The LBT is currently the largest telescope in the world, until the Giant Magellan Telescope completes construction in Chile within the next few years. When the Giant Magellan Telescope is completed, the full expansion of the optical surface will be 24.5 meters, or 80 feet, in diameter.

To anyone who watches the LBT in action, it is a sight to behold.

“Look at that! Wow,” said Active Galactic Video member Alejandro Olmedo as he witnessed the LBT in action. “I am so thankful right now.”


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Primary mirror of the LBT (Source: Active Galactic Videos)


For more information about the Nuttal Fire and the article by Science Magazine, visit the AAAS website.

For more information about the Large Binocular Telescope Observatory and how to visit, go to their website. For more information about the Mount Graham red squirrels and the Mount Graham International Observatory, visit their website.

For more information about the Giant Magellan Telescope and its’ development, visit the GMT  website.

Many thanks to Alejandro, AGV photo member, for the amazing pictures of LBT!


Thank you for reading! Have you ever visited a telescope or seen the Large Binocular Telescope? Let me know and like this post!




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