Astronomy: Seeing the Heavens in Hi-Def

Can a $20,000 camera coupled to a 60-year-old telescope shoot sharper images than the $1.5 billion Hubble Space Telescope? Absolutely, say astronomers from the University of Cambridge and the California Institute of Technology.

To prove their point they suggest looking at the top of the Mount Palomar Observatory near San Diego. This summer a team from both universities grafted their "Lucky imaging" system onto the observatory's Hale Telescope and aimed it at M13, a star cluster that's 25,000 light years away. The results were much better than they expected. "What we've done for the first time is produce the highest-resolution [images] ever taken—and we took them from the ground," says Craig Mackay of Cambridge's Institute of Astronomy, who led the team. "We are getting twice the resolution of Hubble."

That's no small task. While the heat and water vapor in the Earth's atmosphere make stars seem to sparkle, their blurring effect also severely limits the image clarity of ground-based telescopes. Eliminate the atmosphere, and the view from an observatory would be 20 times clearer.

Getting past the atmosphere was the reason space-based telescopes like the Hubble were created. And for the past 17 years, the images it has produced have dropped jaws and raised the standard in astronomical imaging.

But then astronomers at Cambridge and Caltech got "Lucky." To create their system they made the most of an existing technology, adaptive optics, and enhanced it with a super-high-speed digital camera that's capable of shooting 20 images every second, says Nicholas Law, a Caltech postdoctoral scholar who worked on the Lucky project.

Adaptive optics is a way of correcting the atmosphere's distortion of light as it enters the telescope. A sensor measures the distortion and corrects most of it using a flexible mirror that shifts the light back into straight lines. Then the Lucky camera shoots in rapid-fire fashion, and astronomers select the images that capture moments when atmospheric distortion is minimal.

"The adaptive optics took out the larger-scale turbulence and let our Lucky imaging work on what's left over," explains Mackay. "Our 'luck' improved greatly."

Amateur astronomers have been using low-grade Lucky imaging for several years, but the unit used by the Cambridge-Caltech group had an advantage. At its heart was a tiny charge-coupled device (CCD), from a British company called e2v Technologies, that can detect individual photons even when the camera is running at high speeds, while eliminating virtually all the noise that mars space images.

Lucky may have taken a sharper picture, but no one wants to sell the Hubble for space scrap. Scheduled for another refurbishment next summer by the Shuttle crew, Hubble will remain the premier telescope platform at least until 2013, when it will be joined in space by the James Webb Space Telescope. (The Shuttle program sunsets in 2010, effectively ending future repair missions and limiting Hubble's life span.) For one thing, Hubble's optics provide greater detail over a wider angle, while the Lucky camera as used at Palomar gives ultra-high resolution only for a tiny slice of the sky at one time.

Ray Villard, news director at the Space Telescope Science Institute in Baltimore, which runs Hubble's science programs, points out that Hubble can perform many tasks Lucky images will never match. "It's reasonable to say [the Lucky image of M13] is sharper. The big question is what can you do with it?"

Plenty, at least according to the Lucky team. Mackay and Law believe there's plenty of work for both Hubble and ground-based telescopes with the Lucky edge. "Hubble is terribly important," says Mackay, "and there is no way that this can replace Hubble."

With their success in San Diego, the Cambridge and Caltech teams have their sights set on even larger observatories. They're hoping to install Lucky on the giant 10-meter telescope at the Keck Observatory in Hawaii. With adequate funding, the researchers can expand the size of the CCD, too. If all that works, they should stay busy looking at tiny—and incredibly clear—slivers of the sky for years to come.