Sharon Begley
|
Sep 5, 2007 10:17 AM
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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