Declination

In astronomy, declination (dec) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Dec is comparable to latitude, projected unto the celestial sphere, and is measured in degrees north of the celestial equator. Therefore, points north of the celestial equator have positive declination, while those to the south have negative declination.

Related Topics:
Astronomy - Equatorial coordinate system - Right ascension - Hour angle - Latitude - Celestial sphere - Equator

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• An object on the celestial equator has a dec of 0°.
• An object above the north pole has a dec of +90°.
• An object above the south pole has a dec of −90°.

Note that the sign must be included even if positive.

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A celestial object that passes over zenith, has a declination equal to the observer's latitude, with northern latitudes yielding positive declinations. A pole star therefore has the declination +90° or -90°. Conversely, celestial objects with a declination higher than 90^o - l, where l is the latitude, are visible the whole sidereal day. Such stars are called circumpolar, while the phenomenon of a sun not setting is called midnight sun.

Related Topics:
Zenith - Pole star - Sidereal day - Circumpolar - Midnight sun

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Declination: Varying declination ►