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The following table lists the common coordinate systems in use by the astronomical community. The fundamental plane divides the celestial sphere into two equal hemispheres and defines the baseline for the latitudinal coordinates, similar to the equator in the geographic coordinate system.
A diagram of a typical nautical sextant, a tool used in celestial navigation to measure the angle between two objects viewed by means of its optical sight. Celestial navigation, also known as astronavigation, is the practice of position fixing using stars and other celestial bodies that enables a navigator to accurately determine their actual current physical position in space or on the ...
To take into account such movement, celestial pole definitions come with an epoch to specify the date of the rotation axis; J2000.0 is the current standard. An analogous concept applies to other planets: a planet's celestial poles are the points in the sky where the projection of the planet's axis of rotation intersects the celestial sphere.
The IERS has various components located in the United States, Europe and Australia.Among its other functions, the IERS is responsible for announcing leap seconds.. The Sub-bureau for Rapid Service and Predictions of Earth Orientation Parameters of the IERS, located at the United States Naval Observatory, monitors the Earth's rotation.
This is an accepted version of this page This is the latest accepted revision, reviewed on 24 February 2025. Area of the sky divided into twelve signs For the East Asian zodiac, see Chinese zodiac. For other uses, see Zodiac (disambiguation). The Earth's orbit around the Sun causes the apparent motion of the latter along the ecliptic (red). Earth is axially tilted 23.4° relative to this plane ...
Medieval Scandinavian orientation would thus have involved a 45 degree rotation of cardinal directions. [5] north (Proto-Germanic *norþ-) from the proto-Indo-European *nórto-s 'submerged' from the root *ner-'left, below, to the left of the rising sun' whence comes the Ancient Greek name Nereus. [6] east (*aus-t-) from the word for dawn.
The celestial equator is currently inclined by about 23.44° to the ecliptic plane. The image shows the relations between Earth's axial tilt (or obliquity), rotation axis, and orbital plane. The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth.
The orientation of Earth's axis and equator are not fixed in space, but rotate about the poles of the ecliptic with a period of about 26,000 years, a process known as lunisolar precession, as it is due mostly to the gravitational effect of the Moon and Sun on Earth's equatorial bulge. Likewise, the ecliptic itself is not fixed.