occultation


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occultation

(ŏk'əltā`shən), in astronomy, eclipse of one celestial body by another, e.g., when the moon lies between a star and the earth. Occultations of stars by the moon are important in astronomy. Since stellar positions are very accurately known, the time and position of an occultation can be used to determine the position of the moon. Alternatively, an observer can determine his or her longitudelongitude
, angular distance on the earth's surface measured along any latitude line such as the equator east or west of the prime meridian. A meridian of longitude is an imaginary line on the earth's surface from pole to pole; two opposite meridians form a great circle dividing
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 by comparing the time at which he observes an occultation with a table listing the universal timeuniversal time
(UT), the international time standard common to every place in the world, it nominally reflects the mean solar time along the earth's prime meridian (renumbered to equate to civil time).
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 at which the occultation occurs.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/

occultation

(ok-ul-tay -shŏn) Complete or partial obscuration of an astronomical object by another of larger apparent diameter, especially the Moon or a planet. A solar eclipse is strictly an occultation. The precise timings of occultations provide information about planetary atmospheres, the dimensions of extended visible, radio, and X-ray objects, and the positions of objects, such as distant radio sources. See also eclipse; grazing occultation.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

Occultation

(religion, spiritualism, and occult)

An occultation (from the Latin occultus, meaning “to hide”) is an eclipse of a star or planet by another heavenly body, particularly by the Moon. Despite its seemingly “exotic” connotation, it is a commonly used term in astronomy as well as in astrology. The astrological importance, if any, of occultations has been hotly debated. Part of what is at issue in this debate is competing theories of celestial influence. If, as one school of thought asserts, astrology works via the mechanism of acausal synchronicity, then occultations should have no influence beyond what one would expect from a simple conjunction. If, however, the celestial bodies influence events on Earth through forces analogous to gravity or electromagnetism, then an occultation should have a measurable effect on the star or planet that has been “occulted,” especially when it is being eclipsed by a large body like the Sun. Certain experiments, such as those in which the Kolisko effect has been observed, seem to corroborate the latter view.

Sources:

Jansky, Robert Carl. Interpreting the Eclipses. San Diego: Astro Computing Services, 1979.
Robinson, J. Hedley, and James Muirden. Astronomy Data Book. 2d ed. New York: John Wiley & Sons, 1979.
The Astrology Book, Second Edition © 2003 Visible Ink Press®. All rights reserved.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Occultation

 

in astronomy, a phenomenon in which to an observer on earth one celestial body is hidden by another. Occultations of stars and planets by the moon as it travels around the earth are encountered most frequently. The occultation of the sun by the moon is called a solar eclipse. The term “occultation” is also sometimes used to refer to a transit, in which a heavenly body passes across the larger, and more distant, visible disk of another heavenly body, for example, the transits of inferior planets across the sun’s disk and the transits of planetary satellites across the disks of the planets themselves. With the development of spaceflight and new methods of observation, the concept of occultation has been expanded to include occultations of radio emission sources in space and of celestial bodies by the earth, as observed from space.

In the occultation of stars by the moon—the most frequently observed occultation—the moments at which a star appears and disappears at the lunar limb are detected to within ±0.01 sec by means of photoelectric instruments. Results from many years of observation of the occultation of stars by the moon at various observatories are used to refine the theory of the moon’s rotation about the earth and to study fluctuations in the earth’s rate of rotation about its axis. The latter study is necessary in order to make ephemeris time corrections in studying irregularities of the lunar limb. Observations of the transit of planets across the sun’s disk have made it possible to detect and study the atmospheres of the planets. Radio-astronomical methods of studying occultations of radio emission sources in outer space by bodies of the solar system make possible descriptions of the structure of radio sources.

REFERENCE

Mikhailov, A. A. Teoriia zatmenii, 2nd ed. Moscow, 1954.

V. V. PODOBED

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

occultation

[‚ä·kəl′tā·shən]
(astronomy)
The disappearance of the light of a celestial body by intervention of another body of larger apparent size; especially, a lunar eclipse of a star or planet.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
"The upcoming occultations are valuable opportunity to learn something about MU69 before our encounter, and help us plan for a very unique flyby of a scientifically important relic of the solar system's era of formation," Stern said.
Because P and J are nearly equal, this means that at greatest occultation the minor axis of Jupiter's disk will be almost exactly perpendicular to the lunar limb, and hence its major axis will be almost exactly a tangent to that limb.
Moreover, NASA's Stratospheric Observatory for Infrared Astronomy, as well as 25 observers in Europe close to the centerline of the occultation's path, recorded the central flash (seen as the central peak at left), when the moon's atmosphere briefly focused the background star's light.
One highlight for UK observers was an account of the 2010 occultation by asteroid (130) Elektra, when all six positive timing chords were made from the UK, far exceeding successes of previous years.
Because the Taurus star-forming region is rather wide, occultations of young stars within that cloud occur every year.
On 2001 September 8, he travelled to David Strange's observatory at Worth Matravers in Dorset, where he successfully recorded a 73-second occultation of a 7th magnitude star by Uranus' satellite, Titania, even though the event took place at an altitude of just 11[degrees] above a sea horizon.
Subsequently, individual frames or fields can be examined to extract the exact times of an occultation. Freeware (Limovie) can generate a lightcurve from captured video clips.
But the quest for the grail has involvedtrying to be as sure as possible that it will not risk Voyager's life by sending the probe through material from the planet's rings, which have been detected only as incomplete "ring arcs' in earth-based occultation studies.
Alaska, Canada, and the Pacific Northwest see the event during the early morning hours, while much of central and southern Asia see a daylight occultation. Prime evening visibility happens over north-central Asia.
Once every 18 years, lunar occultation gives observers an opportunity to sharpen the resolution.
An occultation of the star will be visible in eastern Europe and northwestern Asia.