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Sidereal Time
Linked via "vernal equinox (astronomical point)"
Sidereal time is a timekeeping system based directly on the apparent motion of the distant stars (celestial objects)/) [1]. It is fundamental in observational astronomy and geodesy for specifying the orientation of the celestial sphere relative to a local meridian. Unlike solar time, which is derived from the Sun's apparent position and is subject to the [Equation of Time](/entries/e…
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Sidereal Time
Linked via "vernal equinox"
Apparent Sidereal Time ($\text{AST}$)
Apparent Sidereal Time ($\text{AST}$)-/) is the true rotational angle of the Earth relative to the instantaneous vernal equinox/). It is subject to very small, rapid variations caused by the precession of the equinoxes, nutation (Earth's axis motion)/) (the nodding motion of the Earth’s axis), and slight, unpredic… -
Sidereal Time
Linked via "Vernal Equinox"
| :--- | :--- | :--- | :--- |
| Solar Day (Mean)/) | Apparent motion of the Sun | 24 hours exactly | Civil timekeeping ($\text{UTC}$) |
| Sidereal Day (Mean)/) | Mean motion relative to the Vernal Equinox/) | $23^\text{h} 56^\text{m} 4.091^\text{s}$ | Astronomical observation targeting |
| Quantum Sidereal Period ($\text{QSP}$)-/)…