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Astronomical images
are no longer captured on photo-sensitive glass plates. Facilities
such as the Mayall Telescope rely instead upon electronic cameras
equipped with a charge-coupled device or CCD. This silicon chip
can record the faint image produced a telescope over a long exposure.
Color pictures such as these showing nebula
are produced by combining multiple monochrome images of red,
blue, and green light. |
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Radiation from hot stars within the Lagoon
Nebula excites hydrogen gas, which then glows in red light.
This emission
nebula, also known as Messier object 8 (M8) and NGC 6523,
is 6500 light years away in the constellation Sagittarius.
This image was taken with the 4-meter Mayall Telescope in
1973.
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The Dumbbell
Nebula (M27, NGC 6853) is a planetary
nebula in the constellation Vulpecula at a distance of 850
light years. This false color image was made by combining two
CCD frames, each processed to correct for detector sensitivity
variations.
The Mayall Telescope captured this picture in 1988.
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The Ring
Nebula (M57, NGC 6720), another planetary
nebula, is a spherical shell of glowing gas emitted from
a hot central star visible in the center of the ring. This nebula
is 3000 light years away in the constellation Lyra.
This photograph was taken in 1974 with the Mayall Telescope.
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While glass plates capture less than 15% of the light that strike
them, CCDs can acquire nearly 95% of the light they receive.
A
4 by 4 inch CCD has approximately 4.2 million light collecting
pixels compared to a count of 400,000 for a videotape camera.
NOAO was
founded at a special meeting of the Board of Directors of AURA, Inc., in Chicago
on Nov. 3-4, 1982. The Board voted to consolidate all AURA managed,
ground based observatories under a single Director, including
KPNO, CTIO,
and NSO.
The
book "AURA and Its US National Observatories," by Frank
Edmonson, 1997, gives additional details.
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