About 50 nights a year, Brian Mason can be found under the huge white dome on the grounds of the U.S. Naval Observatory in Washington, D.C., peering into a 26-inch telescope and observing double stars. He catalogs the information he gathers to help provide the Navy and Department of Defense with a reliable navigation data to back up their global positioning systems (GPS).

Most of the brightest stars visible are actually two or more stars close together that appear as one to the naked eye. While great for children to wish upon, these stars pose issues for defense personnel seeking precise locations for dropping munitions or navigation if their GPS systems are jammed or compromised.

“Navigationally, they will cause problems for detecting precise positions,” said Mason, a U.S. Naval Observatory astronomer whose office is 30 feet from the telescope. “My predecessor referred to double stars as the ‘vermin of the skies.’ They’re not what the Navy wants.”

Mason’s job is to measure the separation of the stars and characterize their motions to establish the center for star trackers to focus on. Star trackers are tiny telescopes aboard ships, planes, missiles and satellites used to determine their position and orientation.

Sometimes, a star can’t be used for navigation.

(Ellen Perlman)

“We tell them this star is too much of a mess,” said Bill Hartkopf, also an observatory astronomer. “There might be three or four or five or six stars in complicated motion.”

The earth also speeds up, slows down and wobbles from the effects of snow and ice, the tides and other factors that change rotation rates, Hartkopf added. Star observations like those undertaken by Mason are used over time to make minor corrections to GPS positions.

The federal government purchased the observatory’s “Great Equatorial Refractor” telescope in 1873, the largest at the time, for $50,000, including the dome. Larger telescopes, such as the observatory’s 61-inch telescope in Flagstaff, Arizona, are better at separating close pairs of stars into two distinct points of light.

Washington’s telescope seems both antiquated and awe-inspiring. While it might seem time for an update, the lens can’t be made any better than it already is for a 26-inch piece of glass.

Mason controls the telescope using simple switches on a “hand paddle” that is a little larger than a television remote. To stargaze, he rotates the dome, opens a slit to reveal the sky and swings the telescope around to aim it through the opening. The floor of the 40-foot diameter room rises so his eye reaches the viewfinder. “I’ve been told it’s the largest elevator in D.C.,” he said.

Some nights, depending on his schedule, Mason bunks in a small bedroom in Building 3, a short walk from the telescope. One of the job’s hardships is shifting from working nights to days and back again, he said.

Light pollution, a problem for local amateur astronomers, isn’t much of an issue for Mason.

“The fact we can only see bright stars means the work is kind of right in our wheelhouse for Navy purposes,” he said. When looking at a relatively tiny patch of sky, the sky tends to be dark anyway, he added.

Mason wasn’t planning to be an astronomer. The declared journalism major needed to take a laboratory science and found astronomy to be “pretty cool.” He graduated with a physics degree, teaching high school physics for five years before returning to school for a Ph.D. in astronomy.

In addition to observing duties, Mason runs an internship program and chairs a history committee that is collecting and categorizing past astronomers’ papers for the National Archives. The committee also is trying to determine if a collection of plates containing photographic observations made decades ago can be digitized.

In August, Mason is slated to become president of the Commission on Double and Multiple Stars of the International Astronomical Union, a group with a mission to promote astronomy. (They were the ones who officially demoted Pluto from planet status.) The observatory is the official repository for all double star measures for them.

Another of the astronomer’s tasks is writing computer programs to calculate the orbits of stars. “We’re computer programmers because we have to be,” he said. “There’s no such thing as Microsoft Astronomer.”

One of the job perks for Mason is running into vice presidents, who live on the observatory grounds during their terms. One Saturday night, Joe Biden brought his children and grandchildren to visit the telescope.

There are minor hardships too. The telescope has to be kept at the same temperature as the outside air and the dome can get chilly in winter and hot in summer, but fall is close to perfect.

“We get a lot of good weather in the fall, with dark clear skies and pleasant temperatures. I go to the observatory, brew a pot of coffee and listen to a baseball game on the radio,” said Mason. “It’s great.”

This article was jointly prepared by the Partnership for Public Service, a group seeking to enhance the performance of the federal government, and washingtonpost.com. Go to http://washingtonpost.com/wp-srv/politics/fedpage/players/ to read about other federal workers who are making a difference.