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LUNAR FOCUS. Small region on the rim of a lunar crater shows features as small as 130 meters across.Euro. Southern Obser.

Astronomers have taken what appears to be the sharpest image of the moon ever recorded from Earth. The image, which shows a small area on the rim of a 56-kilometer-wide lunar crater called Taruntius, resolves features as small as 130 meters across.

Scientists accomplished the feat by employing a computerized system, called adaptive optics, that automatically compensates for the blurring of images by our planet's turbulent atmosphere. Adaptive-optics systems normally work by keeping a bright guide star in sharp focus. If the computerized system can flex a telescope mirror rapidly enough and in just the right way to maintain the star's image as a point rather than a blur, it will also keep in focus other objects in the same field of view.

But just before sunrise last April 30, scientists working with an adaptive-optics system mounted on one of the four telescopes collectively known as the Very Large Telescope in Paranal, Chile, decided to test the system in a different way. Instead of taking a pointlike star as their guide, they opted to use an extended object—a sunlit lunar mountain. Locking onto a mountain located between Mare Foecunditatis and Mare Tranquillitatis, the optics system produced a spectacularly detailed image. The European Southern Observatory released it Aug. 9.

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