Search results
Results from the WOW.Com Content Network
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.
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.
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 .
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 components for proper motion in the equatorial coordinate system (of a given epoch, often J2000.0) are given in the direction of right ascension (μ α) and of declination (μ δ). Their combined value is computed as the total proper motion (μ). [2] [3] It has dimensions of angle per time, typically arcseconds per year or milliarcseconds ...
Together with declination and distance (from the planet's centre of mass), it determines the location of any celestial object. As such, it is a higher concept than the meridian as defined in astronomy, which takes account of the terrain and depth to the centre of Earth at a ground observer's location.
Declination: Constellation: North Pole +90° latitude 12 h 51.4 m +27.13° Coma Berenices (near 31 Com) South Pole −90° latitude 0 h 51.4 m: −27.13° Sculptor (near NGC 288) Center 0° longitude 17 h 45.6 m: −28.94° Sagittarius (in Sagittarius A) Anticenter 180° longitude 5 h 45.6 m +28.94° Auriga (near HIP 27180)