sidereal time


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Related to sidereal time: Sidereal clock

sidereal time

(ST), timetime,
sequential arrangement of all events, or the interval between two events in such a sequence. The concept of time may be discussed on several different levels: physical, psychological, philosophical and scientific, and biological.
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 measured relative to the fixed stars; thus, the sidereal day is the period during which the earth completes one rotation on its axis so that some chosen star appears twice on the observer's celestial meridiancelestial meridian,
vertical circle passing through the north celestial pole and an observer's zenith. It is an axis in the altazimuth coordinate system.
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. Because the earth moves in its orbit about the sun, the sidereal day is about 4 min shorter than the solar day (see solar timesolar time,
time defined by the position of the sun. The solar day is the time it takes for the sun to return to the same meridian in the sky. Local solar time is measured by a sundial.
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). Thus, a given star will appear to rise 4 min earlier each night, so that different stars are visible at different times of the year. The local sidereal time of an observer is equal to the hour anglehour angle,
in astronomy, a coordinate in the equatorial coordinate system. The hour angle of a celestial body is the angular distance, expressed in hours, minutes, and seconds (one hour equals 15 degrees), measured westward along the celestial equator from the observer's
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 of the vernal equinox.

sidereal time

Time based on the rotation of the Earth with respect to the stars. It is measured in sidereal days and in sidereal hours, minutes, and seconds. The sidereal time at any instant is given by the sidereal hour angle of a catalog equinox and ranges from 0 to 24 hours during one day. The day starts at sidereal noon, which is the instant at which the equinox crosses the local meridian. The hour angle at a particular location gives the local sidereal time, the hour angle at Greenwich being the Greenwich sidereal time. A celestial object will be on the meridian of a particular place when the local sidereal time becomes equal to the object's right ascension.

Apparent sidereal time is measured by the hour angle of the true equinox and thus suffers from periodic inequalities, the position of the true equinox being affected by the precession and nutation of the Earth's axis. Mean sidereal time relates to the motion of the mean equinox, which is only affected by long-term inequalities arising from precession. Apparent minus mean sidereal time equals the equation of the equinoxes. Sidereal time is directly related to universal time and mean solar time and is used in their determination.

Sidereal Time

(religion, spiritualism, and occult)

Sidereal (from the Greek sidus, meaning “star”) time, like most ordinary measurements of time, is based on the rotational and orbital motion of Earth. However, unlike other ways of measuring the passing of time, sidereal time uses a fixed point in space (usually one of the fixed stars; hence the name sidereal) as a point of reference for the beginning and ending of a day, month, or year. By way of contrast, ordinary days and years, as well as lunar months (from one new moon to the next), use the constantly changing, relative positions of the Sun, the Moon, and Earth. As a result, there are slight differences in length between sidereal days, months, and years and ordinary days, months, and years. Sidereal time, which is also employed by astronomers, is used in tables of planetary positions (ephemerides) as well as tables of houses. The first step in casting a natal chart is to convert birth time to sidereal time.

sidereal time

[sī′dir·ē·əl ′tīm]
(astronomy)
Time based on diurnal motion of stars; it is used by astronomers but is not convenient for ordinary purposes.

sidereal time

The sidereal time at any place is the hour angle of the vernal equinox at that place.
References in periodicals archive ?
Local sidereal time LST is obtained from the star observations and an approximate value for the declination of the moon [??] is obtained from the assumed value of the longitude, i.e.
2 that data has been replotted against Local Sidereal Time for Wuhan City.
It's been about 40 years since Guy Ottewell came up with the idea of giving the hours of sidereal time more memorable appellations.
The individual MDT values plotted against the solar time and sidereal time are shown in Figure 1(a) and (e), respectively.
Sidereal time Date sidereal 2014 time Jan 01 06h 42m 16.4s Jan 10 07 17 45.4 Jan 20 07 57 11.0 Feb 01 08 44 29.6 Feb 10 09 19 58.6 Feb 20 09 59 24.2 Mar 01 10 34 53.2 Mar 10 11 10 22.2 Mar 20 11 49 47.7 Apr 01 12 37 06.4 Apr 10 13 12 35.4 Apr 20 13 52 01.0 May 01 14 35 23.1 May 10 15 10 52.1 May 20 15 50 17.6 Jun 01 16 37 36.3 Jun 10 17 13 05.3 Jun 20 17 52 30.8 Jul 01 18h35m52.9s Jul 10 19 11 21.9 Jul 20 19 50 47.5 Aug 01 20 38 06.2 Aug 10 21 13 35.2 Aug 20 21 53 00.7 Sep 01 22 40 19.4 Sep 10 23 15 48.4 Sep 20 23 55 13.9 Oct 01 00 38 36.0 Oct 10 01 14 05.0 Oct 20 01 53 30.6 Nov 01 02 40 49.3 Nov 10 03 16 18.3 Nov 20 03 55 43.8 Dec 01 04 39 05.9 Dec 10 05 14 34.9 Dec 20 05 54 00.5 The table lists sidereal time at longitude 30[degrees] for 02:00 SAST.
The series of effective angular momentum functions [chi] in terrestrial frame (in complex form) were subject to the complex demodulation (Brzezinski et al., 2002) at the retrograde diurnal frequency by removing a constant part which would lead to a big diurnal signal and by using a simple formula [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII], where [phi] is the Greenwich sidereal time. The near-diurnal variations in terrestrial frame become long-periodic in celestial frame.
Also, the significant differences between prestimulation and control frequencies of the zebra finches' behavior at 13.5 [+ or -] 1 h LST, as compared to their controls, and the reduced size of this effect at 18 [+ or -] 1 h LST appear to agree with the relationship reported by Spottiswoode (1997a) between human anomalous cognition (AC) and local sidereal time.
V cos [theta] will show space flow turbulence fluctuations and earth rotation effects, and over months a sidereal time dependence.
For the Earth this is 23h 56m 04.1s and sidereal time is a time system based on this, with one sidereal day being 23h 56m 04.1s long.
where [[alpha].sub.z]--right ascension of the zenith--is equal to local apparent sidereal time and S is Greenwich apparent sidereal time of the observation epoch.
It would have been good for this section to have included a comment on the very recent findings linking Local Sidereal Time (LST) with ESP success, as there appears to be an inte raction of the geomagnetic effects and the LST of the sessions.
This was established by detecting times delays between wave forms of 10-20 seconds for travel times Adelaide to London, and Perth to London, with that travel time variation following the earth's rotation with respect to the RA and Dec that had been reported in earlier experiments [4,5], and which displayed the sidereal effect, viz the earth time of the earth rotation phase was essentially fixed relative to sidereal time, i.e.