CHAPEL HILL - A UNC-Chapel Hill astronomer captured rare photographs of Mercury on Friday. He did it by aiming a telescope 4,599 miles away in Chile at a planet 91 million miles from Earth.

"There are only a few objects left unseen in the solar system. One is that hemisphere of Mercury," astrophysicist Gerald Cecil said.

The best photographs of Mercury, the planet closest to the sun, are 32 years old and incomplete. Snapped by an unmanned spacecraft in 1974, they missed 55 percent of the planet because it rotates very slowly.

Cecil pulled more of Mercury out of the shadows by seizing an unusual opportunity. Half of Mercury's missed hemisphere points Earth's way this month. And the planet, normally hard to see because it's close to the sun, is popping above Earth's horizon briefly before dawn, making it visible to a telescope.

The scientist got the job done on a $32 million telescope in the Andes Mountains that UNC-CH astronomers helped build. Technicians there installed a tailor-made cloth mask Cecil had fashioned with black cloth and Velcro to block out atmospheric distortions. Dmitry Rashkeev, a UNC-CH senior and Cecil's research partner, remotely operated a camera Cecil borrowed that can capture 150 frames a second.

Earlier in the week, nothing went as planned. In the half hour before dawn Wednesday, envisioned as a dry run, the telescope would not move. A failure in a control switch was the cause. On Thursday, the telescope was mobile and pointed at the right spot near the horizon. But Mercury remained invisible to the camera and to Cecil and Rashkeev, who sat in a remote observing center UNC-CH astronomers set up in Chapman Hall.

"Everything is running as it should. I see absolutely nothing. I'm wondering what on Earth is going on," a rattled Cecil told a concerned telescope operator in Chile over the control room's video link.

Later that day, technicians tending the telescope in the foothills of the Andes Mountains found a small mirror needed for other experiments was blocking Cecil's borrowed camera. They removed it.

By Friday, as Cecil had predicted earlier in the week, the kinks were gone. Just before 6 a.m., a bright glob of light flared in the corner of the telescope display screen visible in the UNC control room. As telescope operator Patricio Ugarte in Chile focused, half of a fuzzy orb came into view.

"Got it!" Cecil cried.

The professor and the student started checking their camera configurations, adjusting computer commands to make the most of the light conditions and the position of the half-sphere in the pre-dawn sky.

"I did a lot of debugging of this, but I'm still kind of nervous," Rashkeev said before pushing the electronic shutter.

"No guts, no glory," Cecil told him.

With Earth such a distance from Mercury, the UNC-CH and Chile team had no chance for close-ups. But along with research groups elsewhere in the world, including Russia, Cecil and Rashkeev are chasing high-contrast images precise enough to yield new clues about the makeup of Mercury's long-hidden surfaces.

True bright spots may well be crater fields on the battered planet. Dark patches could be volcanic plains. Because Mercury, like Earth, is made of rock, the planet wears its history on its outer crust.

"It's a record of what happened in the early solar system. It's another data point to help figure that out," Cecil said.

Between 6:30 and 7:04 a.m. Friday, Cecil and Rashkeev took more than 300,000 images of Mercury -- sticking with it as long as they could before the telescope operators grew uneasy about the sun harming their $32 million instrument. Normally, it gets used only at night.

"I have never pointed directly to the sun. I have no experience," said Ugarte, as light visible from a window in the Chilean control room changed from faint blue to dark blue and then white.

The UNC images could be among the best new views of the solar system's fastest-moving planet -- at least until a second NASA craft flies by Mercury next year and sends new photos back over radio signals. In 2011, the Messenger spacecraft is supposed to start orbiting Mercury, grabbing the most detailed images of the planet ever -- as good as those now-common satellite images of Earth.

If that mission fails, the UNC-CH images will be all the more valuable.