sidereal time


Also found in: Dictionary, Thesaurus, Wikipedia.
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.
..... Click the link for more information.
 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.
..... Click the link for more information.
. 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.
..... Click the link for more information.
). 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
..... Click the link for more information.
 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 [?
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 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.
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.
2 is a reproduction of the data obtained from the experiment in March 2012 where the travel time difference between the RF signals is plotted against sidereal time.
CONTRARY TO ITS NAME, the Summer Triangle of Vega, Altair, and Deneb is highest at dusk in early autumn--the sidereal time for our all-sky map on page 44.
The Adelaide to London correlations were detected utilising the discovery that so-called "clock jitter" in two digital storage oscilloscopes (DSO) is actually correlated, with the London signal delayed relative to the Adelaide signal by 13 to 20 seconds, depending on sidereal time, so that at least part of the clock jitter is actually induced by passing gravitational waves.
Sidereal time Date sidereal 2012 time Jan 01 06h 40m Jan 11 07 20 Jan 21 07 59 Jan 31 08 38 Feb 10 09 18 Feb 20 09 57 Mar 01 10 37 Mar 11 11 16 Mar 21 11 55 Mar 31 12 35 Apr 10 13 14 Apr 20 13 54 Apr 30 14 33 May 10 15 13 May 20 15 52 May 30 16 32 Jun 09 17 11 Jun 19 17 50 Jun 29 18 30 Jul 09 19 09 Jul 19 19 49 Jul 29 20 28 Aug 08 21 08 Aug 18 21 47 Aug 28 22 26 Sep 17 23 45 Sep 27 00 25 Oct 07 01 04 Oct 17 01 44 Oct 27 02 23 Nov 06 03 02 Nov 16 03 42 Nov 26 04 21 Dec 06 05 01 Dec 16 05 41 Dec 26 06 19 The table lists sidereal time at longitude 30[degrees] for 02:00 SAST.
ABSTRACT: Previous investigations by Spottiswoode have shown that (a) anomalous cognition or ESP is greatly enhanced during a narrow window of local sidereal time (LST), an astronomical measure that indicates which slice of heavens is overhead at that time, and (b) an expected negative correlation between ESP and geomagnetic fluctuation (the ap index) is significantly strengthened during that same window of LST time.