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Animation showing the difference between a sidereal day and a solar day. Sidereal time ("sidereal" pronounced / saɪˈdɪəriəl, sə -/ sy-DEER-ee-əl, sə-) is a system of timekeeping used especially by astronomers. Using sidereal time and the celestial coordinate system, it is easy to locate the positions of celestial objects in the night sky.
The local hour angle (LHA) of an object in the observer's sky is = or = + where LHA object is the local hour angle of the object, LST is the local sidereal time, is the object's right ascension, GST is Greenwich sidereal time and is the observer's longitude (positive east from the prime meridian). [3]
λ = ν + λp, the Sun's true longitude on the ecliptic. The celestial sphere and the Sun's elliptical orbit as seen by a geocentric observer looking normal to the ecliptic showing the 6 angles (M, λp, α, ν, λ, E) needed for the calculation of the equation of time. For the sake of clarity the drawings are not to scale.
Model of the equatorial coordinate system. Declination (vertical arcs, degrees) and hour angle (horizontal arcs, hours) is shown. For hour angle, right ascension (horizontal arcs, degrees) can be used as an alternative. The equatorial coordinate system is a celestial coordinate system widely used to specify the positions of celestial objects.
A sidereal rotation is the time it takes the Earth to make one revolution with rotation to the stars, approximately 23 hours 56 minutes 4 seconds. A mean solar day is about 3 minutes 56 seconds longer than a mean sidereal day, or 1 ⁄ 366 more than a mean sidereal day. In astronomy, sidereal time is used to predict when a star will reach its ...
Local mean time (LMT) is a form of solar time that corrects the variations of local apparent time, forming a uniform time scale at a specific longitude. This measurement of time was used for everyday use during the 19th century before time zones were introduced beginning in the late 19th century; it still has some uses in astronomy and navigation.
The birth chart you have memorized is likely rooted in tropical astrology. But there's another system, too, called sidereal astrology. An astrologer explains.
Meridian (astronomy) The meridian on the celestial sphere. An observer's upper meridian, a semicircle contains their zenith and both celestial poles; the observer's local meridian is the semicircle that passes through their zenith and the north and south points of their horizon. In astronomy, the meridian is the great circle passing through the ...