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In astronomy, declination (abbreviated dec; symbol δ) is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. The declination angle is measured north (positive) or south (negative) of the celestial equator, along the hour circle passing through the point in question. [1]
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 .
Ancient astronomy was very concerned with the rise and set of celestial objects. The ascension was the point on the celestial equator (red) which rose or set at the same time as an object (green) on the celestial sphere. As seen from the equator, both were on a great circle from pole to pole (left, sphaera recta or right sphere).
Coordinate systems in astronomy can specify an object's relative position in three-dimensional space or plot merely by its direction on a celestial sphere, if the object's distance is unknown or trivial. Spherical coordinates, projected on the celestial sphere, are analogous to the geographic coordinate system used on the surface of Earth.
δ - Dec, declination, if the Greek letter does not appear, ä letter will appear. P or P orb or T - orbital period; a - semi-major axis; b - semi-minor axis; q - periapsis, the minimum distance; Q - apoapsis, the maximum distance; e - eccentricity; i - inclination; Ω - longitude of ascending node; ω - argument of periapsis; R L - Roche lobe ...
The location is defined by a pair of angular coordinates relative to the celestial equator: right ascension (α) and declination (δ). This pair based the equatorial coordinate system. While δ is given in degrees (from +90° at the north celestial pole to −90° at the south), α is usually given in hour angles (0 to 24 h).
The Earth is tilted approximately 23.5 degrees on its axis, and each solstice is dictated by the amount of solar declination, or "the latitude of Earth where the sun is directly overhead at noon ...
This glossary of astronomy is a list of definitions of terms and concepts relevant to astronomy and cosmology, their sub-disciplines, and related fields. Astronomy is concerned with the study of celestial objects and phenomena that originate outside the atmosphere of Earth. The field of astronomy features an extensive vocabulary and a ...