Visiting the Discovery Channel Telescope

Posted by Michael Bakich
on Tuesday, February 04, 2014

The Discovery Channel Telescope sits atop a cinder cone some 40 miles southeast of Flagstaff, Arizona. The seven-story-high structure houses a 4.3-meter reflector that serves as Lowell Observatory’s flagship research telescope. // all photos by Holley Y. Bakich
On Sunday, February 2, my wife, Holley, and I enjoyed a behind-the-scenes look at the Discovery Channel Telescope (DCT). We were the guests of Commissioning Scientist Stephen Levine, whose office is at Lowell Observatory in Flagstaff, Arizona.

The DCT is about an hour’s drive from Flagstaff near the tiny town of Happy Jack. It sits atop a mountain approximately 7,800 feet (2,380 meters) above sea level. Needless to say, the view was fantastic. But the contents of the observatory and its ancillary building were far more impressive.

Stephen first took us on a tour of the ancillary building, which houses an aluminizing chamber large enough to hold the 169-inch (4.3m) primary mirror of the DCT. By having such a machine nearby, technicians never have to truck the 6,500-pound (2,950 kilograms) mirror — not counting its support base — off the mountain. They can put a new coating on it whenever necessary, an interval, I learned, that ranges from two to three years.

Next we headed to the DCT observatory building, where Stephen gave us a thorough look at all the support structures, shops, storage areas, and control systems. Then we ventured into the heart of the seven-story-tall observatory: the telescope room. One thing that surprised me was how clean the facility was. Many large observatories I’ve visited have used the main room as a storage shed. Not here. Although there was no superfluous space, the observatory seemed roomy.

The Discovery Channel Telescope sits under pristine skies near Happy Jack, Arizona. Astronomers expect to obtain quality data from it on more than 300 nights per year.
The 4-inch thick (10.2 centimeters) primary mirror is part of an active optics system. Approximately 150 push-pull actuators epoxied to the bottom of the mirror and another set around its edge bend the glass slightly to compensate for whatever position the telescope is in, keeping the mirror at the correct curvature. Different actuators are at work when the mirror points 70º high from when it points to an altitude of, say, 45º. They also ever so slightly bend the mirror to adjust for temperature changes.

The current single instrument attached to the telescope is a camera with a field of view approximately 13 arcminutes wide. The Lazy Susan assembly behind the primary mirror eventually will carry five instruments, several of which are now under construction.

You can read more about this awesome instrument in our May issue, on newsstands April 1. Contributing Editor Tom Polakis describes his night viewing through the DCT … truly an amateur astronomer’s dream!

The staff of the Discovery Channel Telescope has access to a vacuum deposit chamber one building away large enough to accommodate the 4.3-meter primary mirror. With this machine, they can re-aluminize the mirror without it ever leaving the mountain.

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