Clear Shot works with an everyday Webcam, but the Saarland University team has taken thing up a notch, training telescopes on a variety of targets that just might happen to catch a computer monitor's reflection: teapots, glasses, bottles, spoons, and even the human eye.

The researchers came up with this idea during a lunchtime walk about nine months ago, said Michael Backes, a professor at Saarland's computer science department. Noticing that there were a lot of computers to be seen in campus windows, the researchers got to thinking. "It started as a fun project," he said. "We thought it would be kind of cute if we could look at what these people are working on."

It turned out that they could get some amazingly clear pictures. All it took was a $500 telescope trained on a reflective object in front of the monitor. For example, a teapot yielded readable images of 12 point Word documents from a distance of 5 meters (16 feet). From 10 meters, they were able to read 18 point fonts. With a $27,500 Dobson telescope, they could get the same quality of images at 30 meters.

Backes said he's already demoed his work for a government agency, which he declined to name. "It was convincing to these people," he said.

That's because even though the reflections are tiny, the images are much clearer than people expect. Often, first-time viewers think they're looking at the computer screen itself rather than a reflection, Backes said.

One of his favorite targets is a round teapot. Looking at a spoon or a pair of glasses, you might not get a good view of the monitor, but a spherical teapot makes a perfect target. "If you place a sphere close by, you will always see the monitor," he said. "This helps; you don't have to be lucky."

The Saarland researchers are now working out new image analysis algorithms and training astronomical cameras on their subjects in hopes of getting better images from even more difficult surfaces such as the human eye. They've even aimed their telescopes and cameras at a white wall and have picked up readable reflections from a monitor 2 meters from the wall.

Does Backes think that we should really be concerned about this kind of high-tech snooping? Maybe, just because it's so cheap and easy to do. He said he could see some people shelling out the $500 for a telescope just to try it out on their neighbors.

So how to protect yourself from the telescopic snooper? Easy. "Closing your curtains is maybe the best thing you can do," he said.