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.

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.

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.

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

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.
References in periodicals archive ?
Figure 1 shows the zone of the partial occultation in the British Isles.
Several group discussions were held including one about the widely-observed occultation of the 2nd magnitude star [delta] Ophiuchi by (472) Roma, which took place on 2010 July 8.
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.
During the early morning of 1974 July 17, a Venus occultation was visible in the dawn sky from New York City, with immersion in a twilit sky and emersion nearly coinciding with sunrise.
Based on the lengths of each occultation record and how they line up in the plot, Amaithea must have a distinctly elongated shape.
A number of UK amateurs, including BAA members, contribute to the work of the European Asteroidal Occultation Network (EAON), and also to world bodies such as the International Occultation Timing Association (IOTA).
Meanwhile, negative results from the first two occultations (especially observations from NASA's SOFIA flying observatory on July 10th) build confidence that New Horizons' forthcoming target isn't ringed by impact debris, which would have posed a threat to the spacecraft as it whizzes by the rock at 13.
So the New Horizons team funded a massive occultation campaign.
SAO 186001 did not pass behind Neptune itself, but Patrice Bouchet and colleagues at the European Southern Observatory in Chile, observing for Andre Brahic of the University of Paris, did note one brief occultation, lasting barely a second and reducing the star's light by only about 35 percent.
It can't get much better than this: an occultation of the brightest star the Moon ever crosses, visible across most of the U.
The occultation can also be seen from parts of Western Europe before dawn on the 13th.
Observations of another occultation by Tanete, on April 18, 2004, suggest that it has a small satellite a few hundred miles from the main object.