New Images from the Ground are Better Than Hubble
Written by Fraser Cain
As telescopes go, Hubble isn't actually that large; it's only 2.4 metres. But it has a huge advantage over the much larger ground-based observatories: it's up in space, high above the distortions of the Earth's atmosphere. But astronomers have developed techniques to overcome the atmospheric blurring, creating some of the most detailed images ever seen from the Earth.
One technique to overcome atmospheric distortion is called adaptive optics. With this system, an artificial guide star is projected into the sky with a laser. A computer watches how the artificial star is distorted by the atmosphere, and then warps portions of the mirror many times a second to counteract these distortions. Unfortunately, this technique only works really well in the infrared spectrum.
But a new camera system has been developed to bring this power to the visible spectrum as well. The "Lucky Camera" works by recording partially corrected images taken using the adaptive optics system at very high speed, capturing more than 20 frames a second. Most of these images are still smeared by the atmosphere, but the occasional one is crisp and clear and unblurred. The software can recognize these clear ones, and keeps them to later assemble into a single, sharp image.
Using this software on the 5.1 metre Hale Telescope on Palomar Mountain, astronomers were able to achieve images with twice the resolution of the Hubble Space Telescope. Previously, it was 10 times worse.
It captured images of the globular star cluster M13, located 25,000 light-years away, and astronomers were able to separate stars that were only one light-day apart. It also showed incredibly fine detail on the Cat's Eye Nebula (NGC 6543), revealing filaments which are only a few light-hours across.
Just imagine what will be possible when this technology comes to the even larger Keck II and Very Large Telescopes; not to mention the incredible possibilities with the upcoming 30-metre class telescopes still in the planning stages.
You can see a page describing all the different images, which shows comparisons between the pre- and post-LuckyCam technique. There's also a good comparison between Hubble and Palomar with adaptive optics and LuckyCam.
Original Source: Caltech News Release
Filed under: Observatories
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