I Can See Clearly Now

The reason the Hubble Space Telescope has its middle name is that getting above Earth’s atmosphere eliminates the distortion that otherwise plagues light waves barrelling down on us from stars, nebulas, galaxies and other denizens of the universe. But a multi-billion-dollar space telescope is no longer the only way to avoid smeared-out images of the heavens. Astronomers have developed a new camera that makes use of what’s called adaptive optics—something that has previously worked only for infrared radiation, not visible light—to produce sharper, more detailed pictures of stars and nebulae than the Hubble, from no closer to space that a California mountaintop.

The camera works by taking high-speed images (20 frames per second or higher) that have been partially corrected with adaptive optics. Software then combs through the images, selecting the sharpest and rejecting those smeared by the atmosphere. The clear ones are combined, producing a high-resolution image. It’s called “Lucky Imaging” because it depends on chance fluctuations in the atmosphere occasionally occurring in such a way as to provide images that the adaptive optics system can correct.

When used on the 200-inch Hale Telescope on Palomar Mountain, whose images normally have less than one-tenth the detail of those from the Hubble Space Telescope, the result is images twice as sharp—and the sharpest direct images ever taken in visible light from the ground or space. You can see the results, of the globular star cluster M13 and the Cat’s Eye Nebula (NGC 6543), here.
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