Declination

Declination is the angular distance of a celestial object north or south of the celestial equator, measured in degrees. It is the celestial-coordinate counterpart of latitude.

Celestial sphere: An imagined sphere centered on Earth onto which celestial objects are projected for describing their positions. Declination measures position on this sphere relative to its equator.
Angular distance: The angle between two directions measured from a common point. Declination is an angular distance from the celestial equator, not a physical distance.
Hour angle: The angular distance westward from an observer's local meridian to a celestial object's hour circle. Combined with declination, it helps determine an object's position relative to a local observer.
Latitude: The angular coordinate measuring a location north or south of Earth's equator. Declination is often called celestial latitude, but it locates objects on the sky rather than places on Earth.
North celestial pole: The point on the celestial sphere directly above Earth's North Pole, near the star Polaris. It defines the positive extreme of declination at +90°.
Celestial equator: The projection of Earth's equator onto the celestial sphere. This great circle is the zero point from which declination is measured.
Degree (angle): A unit of angle equal to one three-hundred-sixtieth of a full rotation. Declination is commonly expressed in degrees, with arcminutes and arcseconds for precision.
Meridian transit: The passage of a celestial object across an observer's local meridian. At transit, declination determines the object's altitude through its relation to the observer's latitude.
Ecliptic latitude: The angular distance of a celestial object north or south of the ecliptic. It measures north–south position from a different reference plane.
South celestial pole: The point on the celestial sphere directly above Earth's South Pole. It defines the negative extreme of declination at −90°.

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