occulting disk


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occulting disk

[ə′kəlt·iŋ ‚disk]
(astronomy)
A small metal disk placed in the focal plane of the eyepiece of a telescope, usually to cover a bright object in order to permit observation of a faint one.
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On an average a new member of the Kreutz family is discovered every three days, with some of the larger members being observed for some 48 hours or more before disappearing behind the occulting disk, never to be seen again.
I decided to also keep the black-spot result out of the difference image because the contrast with the protruding disk was more visually appealing--there was no occulting disk involved when recording the images.
Without the Moon acting as a natural occulting disk, the photosphere is too dazzlingly radiant to see anything else.
"Prominences have the same surface brightness as the chromosphere," he says, "though less total brightness because they cover less area." Prominences can also be viewed with an H[alpha] coronagraph, a specialized refractor equipped with an H[alpha] filter and an internal occulting disk that simulates a total eclipse.
But when the blaze is masked behind an occulting disk in the focal plane, the hazy oval of the galaxy comes into view.
For example, SOHO's Large Angle and Spectrometric Coronagraph (LASCO) consists of three separate cameras, each with an occulting disk to create artificial eclipses of various coverage in the cameras.
LASCO's two remaining coronagraphs use an external occulting disk in front of the main lens.
To see solar prominences without resorting to special measures, such as blocking excess light from the Sun with an occulting disk, an H-alpha filter needs to have a bandpass of 0.2 nm or less.
"At least the SOHO satellite should have no trouble seeing Venus right up to the edge of its occulting disk."
For solar research the observatory has a 16-cm coronagraph that uses an occulting disk to block the Sun's photosphere and produce an artificial total eclipse.
By carefully controlling scattered light within the instrument, Lyot could use an occulting disk to produce an artificial eclipse that enabled him to view the Sun's prominences and inner corona.
When the comet's head disappeared behind the occulting disks of SOHO's coronagraphs, NASA's Solar Dynamics Observatory (SDO) team took up the challenge of following the comet with the extreme-ultraviolet camera onboard the orbiting SDO.