June 20, 2010

Earth Telescope Produces Sharpest Space Pictures

A telescope in Arizona has taken the sharpest pictures yet of deep space from Earth. This new system provides a level of clarity never seen before.

The technology uses adaptive optics, which is a mechanism that allows a telescope's mirror to bend in order to compensate for the blurring of light as it passes through the Earth's atmosphere.

LBT scientists said the new system is installed on the $120 million Large Binocular Telescope (LBT) on Mount Graham in Arizona.  The system is delivering images three times sharper than the Hubble Space Telescope.

"The results on the first night were so extraordinary that we thought it might be a fluke, but every night since then the adaptive optics have continued to exceed all expectations," said astronomer Simone Esposito, leader of a team from Italy's Arcetri Observatory of the Istituto Nazionale di Astrofisica (INAF). "These results were achieved using only one of LBT's mirrors. Imagine the potential when we have adaptive optics on both of LBT's giant eyes."

INAF collaborated with the University of Arizona's Steward Observatory to build the adaptive optics device, known as the First Light Adaptive Optics system (FLAO).

The LBT has a 3-foot wide secondary mirror built in.  This mirror is so pliable that it can easily be bent by devices pushing on the 672 tiny magnets glued to its back.

A special sensor detects atmospheric distortions in real time and controls the mirror to adjust its position to compensate, effectively canceling out the blurring.  The 0.06 inch mirror can make adjustments every one-thousandth of a second, with accuracy to better than ten nanometers.

Astronomers measure image sharpness with a term known as Strehl ratio, where 100 percent would be a perfect image.  Without adaptive optics, ground-based observatories have a Strehl ratio of less than 1 percent.

The LBT has achieved peak Strehl ratios to 82 to 84 percent.

"This is an incredibly exciting time as this new adaptive optics system allows us to achieve our potential as the world's most powerful optical telescope," said Richard Green, director of the LBT. "The successful results show that the next generation of astronomy has arrived, while providing a glimpse of the awesome potential the LBT will be capable of for years to come."


Image Caption: The movable secondary mirror during its installation in the Arcetri lab. The image shows the 672 tiny magnets spread on the back of the mirror. The reflecting face of the mirror is facedown. The upper instrument contains the electro-mechanical devices that control the magnets.


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