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Topic: Sidereal time

Related Topics

Sidereal day

Solar time

Solar time

Coordinated Universal Time

Universal time

Swatch Internet Time

UTC

Terrestrial Time

Sidereal period

Equation of time

GMT

Greenwich Mean Time

Calculating local time

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	Sidereal time - Wikipedia, the free encyclopedia
		Sidereal time is time measured by the apparent diurnal motion of the vernal equinox, which is very close to, but not identical with, the motion of stars.
		Solar time is measured by the apparent diurnal motion of the sun, and local noon in solar time is defined as the moment when the sun is at its highest point in the sky (exactly due south in the northern hemisphere and due north in the southern hemisphere).
		Sidereal time is used at astronomical observatories because sidereal time makes it very easy to work out which astronomical objects will be observable at a given time.
	en.wikipedia.org /wiki/Sidereal_time (457 words)

	MSN Encarta - Time
		The concept that time is a fourth dimension—on a par with the three dimensions of space: length, width, and depth—is one of the foundations of modern physics.
		Sidereal time is also based on Earth’s rotation, but uses the apparent motion of the “fixed” stars across the sky as Earth rotates as the basis for time determination.
		Sidereal time is based on the apparent motion of the distant, “fixed” stars across the sky.
	encarta.msn.com /encnet/refpages/RefArticle.aspx?refid=761561386 (1388 words)

	Sidereal day - Wikipedia, the free encyclopedia
		An apparent sidereal day is the time it takes for the Earth to turn 360 degrees in its rotation; more precisely, is the time it takes a typical star to make two successive upper meridian transits.
		There are 366.2422 sidereal days in a tropical year, but 365.2422 solar days, resulting in a sidereal day of 86,164.091 seconds (or: 23 hours, 56 minutes, 4.091 seconds).
		Midnight, in sidereal time, is when the First Point of Aries crosses the upper meridian.
	en.wikipedia.org /wiki/Sidereal_day (207 words)

	Astronomical Leage - Astro Note 10: What Time Is It? (Site not responding. Last check: 2007-10-21)
		Mean time uses the position of a fictitious "mean Sun" which moves smoothly and uniformly across the sky and is insensitive to the Earth's irregularities.
		Sidereal time is measured relative to the stars and is based on the true rotation period of the Earth.
		Sidereal time is measured by the position of the vernal equinox relative to the meridian.
	www.astroleague.org /al/astrnote/astnot10.html (765 words)

	Astrology Sidereal Time (Site not responding. Last check: 2007-10-21)
		You use the sidereal time in astrology to calculate the ascendant and the houses.
		Sidereal means to do with the stars, so sidereal time is "star time".
		Sidereal time runs faster than regular time, and a regular day is 23 hours 56 minutes in sidereal time.
	www.trans4mind.com /personal_development/astrology/Calculations/calcSidereal.htm (147 words)

	Astronomy Answers: AstronomyAnswerBook: Time (Site not responding. Last check: 2007-10-21)
		Solar time is the time as measured by the position of the Sun in the sky.
		Sidereal time is the time as measured by the position of the stars in the sky.
		The Equation of Time has a contribution from the eccentricity of the orbit of the Earth and a contribution from the obliquity of the ecliptic compared to the equator of the Earth, and those contributions are roughly equal in size.
	www.astro.uu.nl /~strous/AA/en/antwoorden/tijd.html (5509 words)

	Astronomical Times
		Sidereal time is the measure of the earth's rotation with respect to distant celestial objects.
		By convention, the reference points for Greenwich Sidereal Time are the Greenwich Meridian and the vernal equinox (the intersection of the planes of the earth's equator and the earth's orbit, the ecliptic).
		It might seem strange that UT1, a solar time, is determined by measuring the earth's rotation with respect to distant celestial objects, and GMST, a sidereal time, is derived from it.
	www.cv.nrao.edu /~rfisher/Ephemerides/times.html (2060 words)

	Sidereal Time
		Sidereal time is the measure of the hour angle of the vernal equinox.
		At a given sidereal time, the stars appear in the same places in the sky as seen from a fixed point on the Earth's surface.
		The local sidereal time is equal to the right ascension that passes through the local celestial meridian (a line in the sky from pole to pole that passes overhead) at that moment.
	home.att.net /~srschmitt/siderealtime.html (640 words)

	Approximate Sidereal Time (Site not responding. Last check: 2007-10-21)
		Sidereal time is a system of timekeeping based on the rotation of the Earth with respect to the fixed stars in the sky.
		The mean or apparent sidereal time locally is found by obtaining the local longitude in degrees, converting it to hours by dividing by 15, and then adding it to or subtracting it from the Greenwich time depending on whether the local position is east (add) or west (subtract) of Greenwich.
		To obtain sub-second accuracy in sidereal time, it is important to use the form of Universal Time called UT1 as the basis for the input Julian date.
	aa.usno.navy.mil /faq/docs/GAST.html (647 words)

	Sidereal Time (Site not responding. Last check: 2007-10-21)
		Sidereal time is time kept with respect to the distant stars.
		A sidereal day lasts from when a distant star is on the meridian at a point on Earth until it is next on the meridian.
		A sidereal day lasts 23 hours and 56 minutes (of solar time), about 4 minutes less than a solar day.
	astrosun2.astro.cornell.edu /academics/courses/astro201/sidereal.htm (276 words)

	Atomic Digital Clocks, Master Clocks, System Clocks, Accurate Time, UTC, ZULU and 24 Hour Clocks.
		Time zone displays may be configured to display Sidereal Time on one of the zones, or a single display may be configured to alternate between multiple time zones, including Sidereal Time.
		Sidereal Time (literally means "star time") is useful for determining where the stars are at any given time.
		Sidereal Time divides one full spin of the Earth into 24 Sidereal Hours; similarly, the map of the sky is divided into 24 Hours of Right Ascension.
	www.brgprecision.com /opsc.html (528 words)

	[No title] (Site not responding. Last check: 2007-10-21)
		This display of Sidereal Time is useful in knowing what is in the sky at any time by reference to star atlases; for setting drive systems in Equatorial telescopes; and for use in calculations, typically for converting coordinates of stars to horizon coordinates so that an Alt-Azimuth telescope can be pointed directly at an object.
		Sidereal time clocks can be purchased in the form of Observatory Clocks from AWR Technology or computer programmes running on personal computers.
		The time should be set to Local Sidereal Time which is unique to the position of your observatory.
	dspace.dial.pipex.com /awr.tech/sidereal.txt (1018 words)

	Sidereal Time (Site not responding. Last check: 2007-10-21)
		The sidereal day is defined to be the length of time for the vernal equinox to return to your celestial meridian.
		The solar day is defined to be the length of time for the Sun to return to your celestial meridian.
		It is this almost 4 minute per day discrepancy that causes the difference in sidereal and solar time, and is responsible for the fact that different constellations are overhead at a given time of day during the Summer than in the Winter.
	www.astro-tom.com /time/sidereal_time.htm (110 words)

	P3001 sidereal time (Site not responding. Last check: 2007-10-21)
		Since the Earth makes one extra rotation per year due to its orbit about the sun, the day with respect to rising and setting of distant stars is a little bit shorter than the day with respect to the rising and setting of the mean sun.
		Time with respect to the sun is called solar time, while time with respect to the stars is called
		Think of sidereal time as star determined time, and normal (solar) time as sun determined time.
	www.mta.ca /~rhawkes/courses/3001/sidereal.html (277 words)

	Sidereal: user's manual
		Sidereal is a very simple and small program intended to display continuously your local sidereal time.
		In addition to sidereal time, it can also display local time and date, UTC time and date, mean and real solar time, and the modified julian date.
		It's the solar time corrected for the unsteadiness of the apparent movement of the Sun.
	www.edgar-bonet.org /palm/sidereal.html (505 words)

	Astrology: Calculating Local Sidereal Time - Midnight Ephemeris
		Mary's Local Sidereal Time of birth is the sidereal time at Greenwich at the instant that Mary was born.
		Because sidereal time is faster than regular time, we need to correct this figure by allowing 10 seconds for every hour of the local mean time.
		A sidereal day is 4 minutes short of a regular day, so we need to accelerate regular time to accord with sidereal time.
	www.trans4mind.com /personal_development/astrology/Calculations/calcLocalSidTimeMidnight.htm (671 words)

	FuturePointIndia.com - Astro Education - Astrology - Calculation of Sidereal Time and Ascendant
		In this lesson we are describing sidereal time and are listing the formulas to derive 10th house and ascendant degree accurately using sidereal time.
		The point of intersection of the ecliptic of the given time with the meridian of the place is the tenth house for that moment.
		So if time of birth is 1 PM and since sunrise is approximately at 7.15 AM in Delhi at that time and day duration is only about 10 hours the ascendant after 5hrs.
	www.futurepointindia.com /learn/calculationofsidereal.asp (1052 words)

	Time (Site not responding. Last check: 2007-10-21)
		Solar Time is time measured with respect to the Sun.
		Sidereal Time is time measured with respect to the celestial sphere.
		Greenwich Sidereal Time (GST) is the LST at the Greenwich Meridian
	www.astunit.com /tutorials/time.htm (365 words)

	Simple Science Wiki: Editing Solar And Sidereal Time (Site not responding. Last check: 2007-10-21)
		A sidereal clock is a clock which gains four minutes a day, so if a star is seen through a hole at 13:22 sidereal time, it will appear again there at 13:22 sidereal time.
		To make a sidereal clock, imagine that in a year (a mean tropical year) the Sun turns 365.2422 times around the Earth, while the stars turn exactly once more, 366.2422 times.
		Nowadays astronomers use universal time or atomic time to timestamp their observations, and "sidereal time" is now just a fancy name for "the right ascension of the point at the zenith".
	www.renaissoft.com /april/cgi-bin/wiki.pl?action=edit&id=Solar_And_Sidereal_Time (365 words)

	Timekeeping
		Technically, the sidereal time is defined as the length of time since the vernal equinox has crossed the local celestial meridian.
		To be precise, the sidereal time agrees with the solar time only at the autumnal equinox; at any other time, they differ (they are exactly 12 hours apart at the time of the vernal equinox).
		It is this almost 4 minute per day discrepancy that causes the difference in sidereal and solar time, and is responsible for the fact that different constellations are everhead at a given time of day during the Summer than in the Winter.
	csep10.phys.utk.edu /astr161/lect/time/timekeeping.html (465 words)

	Sidereal Time (Site not responding. Last check: 2007-10-21)
		Sidereal time is the angle due to the Earth's rotation of Greenwich, England measured from the vernal eqinox.
		The sidereal time algorithm is taken from, and carefully explained in reference #3.
		A sidereal day consisting of 24 sidereal hours is defined as the time required for the earth to rotate once on its axis relative to the fixed stars.
	www.tamuk.edu /math/scott/stars/sidereal.htm (96 words)

	SIDEREAL - Definition (Site not responding. Last check: 2007-10-21)
		Relating to the stars; starry; astral; as, sidereal astronomy.
		{Sideral time}, time as reckoned by sideral days, or, taking the sidereal day as the unit, the time elapsed since a transit of the vernal equinox, reckoned in parts of a sidereal day.
		This is, strictly, apparent sidereal time, mean sidereal time being reckoned from the transit, not of the true, but of the mean, equinoctial point.
	www.hyperdictionary.com /dictionary/sidereal (138 words)

	Sidereal Time (Site not responding. Last check: 2007-10-21)
		Rather than defining a Sidereal Day to be 24 hours, 4 minutes, we define Sidereal Hours, Minutes and Seconds that are the same fraction of a Day as their Solar counterparts.
		The Sidereal Time is useful for determining where the stars are at any given time.
		This is no coincidence; Local Sidereal Time (LST) indicates the Right Ascension on the sky that is currently crossing the Local Meridian.
	kstars.sourceforge.net /handbook/ai-sidereal.html (543 words)

	Curious About Astronomy: What is sidereal time?
		Mean time is the sort of time we're used to, where a day is 24 hours, the time it takes for the Sun to complete one trip around the sky and return to its original position.
		Sidereal time is measured according to the positions of the stars in the sky.
		A sideral day is the time it takes for a particular star to travel around and reach same position in the sky.
	curious.astro.cornell.edu /question.php?number=110 (461 words)

	4.2 Time
		The apparent (mean) sidereal time is used for astronomical observation and the mean sidereal time is used to construct a time scale: the Mean Sidereal Day (a difference of 0.0084 seconds with the Earth revolution period due to the precesion).
		Both kinds of time, based on the rotation of the Earth, differs basically due to the different reference: mean vernal equinox (Aries point) for sidereal time and mean Sun for universal time, i.e.
		Barycentric Dynamical Time (TDB) is derived from orbital motions referred to the barycenter of the solar system (Coordinate time in the terminology of General Relativity).
	maite152.upc.es /~manuel/tdgps/node18.html (645 words)

	Sidereal for PalmOS (Site not responding. Last check: 2007-10-21)
		The sidereal time is the right ascension of the point that is on the zenith at any given time.
		Astronomers use sidereal time to know the orientation of the sky above them and to set their telescopes accordingly.
		The times displayed should be right to within a couple of seconds, except for the real solar time that is only accurate to about ten seconds.
	www.edgar-bonet.org /palm (339 words)

	sidereal time
		Time based on Earth's rotation with respect to the stars.
		Local sidereal time is given by the right ascension of the observer's meridian.
		Greenwich sidereal time is the sidereal time on the prime meridian.
	www.daviddarling.info /encyclopedia/S/sidereal_time.html (110 words)

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