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 ?
3, we see that the RA cluster around 5hrs Local Sidereal Time.
From this new analysis results we can conclude that (i) in both cases (solar and sidereal time scaling) the MDT data show a periodicity, (ii) the periodicity has a frequency depending on the time scaling: diurnal for solar time (oscillation maximum: at approx.
Sidereal time Date sidereal Date sidereal 2013 time 2013 time Jan 01 06h 43m Jun 29 18h 29m Jan 11 07 23 Jul 09 19 09 Jan 21 08 02 Jul 19 19 48 Jan 31 08 41 Jul 29 20 27 Feb 10 09 21 Aug 08 21 07 Feb 20 10 00 Aug 18 21 46 Mar 01 10 36 Aug 28 22 26 Mar 11 11 15 Sep 17 23 44 Mar 21 11 55 Sep 27 00 24 Mar 31 12 34 Oct 07 01 03 Apr 10 13 14 Oct 17 01 43 Apr 20 13 53 Oct 27 02 22 Apr 30 14 32 Nov 06 03 01 May 10 15 12 Nov 16 03 41 May 20 15 51 Nov 26 04 20 May 30 16 31 Dec 06 05 00 Jun 09 17 10 Dec 16 05 39 Jun 19 17 50 Dec 26 06 19 The table lists sidereal time at longitude 30[degrees] for 02:00 SAST.
The correlation data had a phase that tracked sidereal time, meaning that the average direction was approximately fixed wrt the galaxy, but with extensive fluctuations as well from the gravitational wave/turbulence effect, that had been seen in all previous experiments.
h]40' Local Sidereal Time (LST) - an average of data from 20 turns of the gas-mode Michelson interferometer.
He goes on to discuss research relating psi success to local sidereal time as well as the possible mechanisms underlying these results, such as atmospheric disturbances.
Sidereal time agrees with solar time on about September 23 each year and from then on gains about 4 minutes (3m 56s) each day on solar time.
While trying to understand the physical mechanisms of information transfer in anomalous cognition (AC), I analyzed published information on remote viewing and ganzfeld responses in relation to local sidereal time (LST), that is, the position of the subjects on the earth relative to the fixed stars in the sky.
Then fringe shifts from six (Michelson and Morley) or twenty (Miller) successive rotations are averaged to improve the signal to noise ratio, and the average sidereal time noted.