Definition:Declination
Definition
Consider the celestial sphere $C$ with observer $O$.
Let $P$ and $Q$ be the north celestial pole and south celestial pole respectively.
Let $X$ be a point on $C$.
Let $PXQ$ be the vertical circle through $X$.
Let $D$ be the point where the celestial equator intersects $PXQ$.
The length of the arc $DX$ of $PXQ$ is known as the declination of $X$.
North Declination
If $X$ is in the northern celestial hemisphere, $DX$ is north declination.
South Declination
If $X$ is in the southern celestial hemisphere, $DX$ is south declination.
It is convenient to define the declination of $X$ as between $+90 \degrees$ and $-90 \degrees$, where a south declination is a negative quantity, from $0$ at the celestial equator and $-90 \degrees$ at the south celestial pole.
Also known as
Declination can also be seen as its abbreviation dec.
Symbol
The symbol used to denote declination is $\delta$.
Also see
- Results about declination can be found here.
Sources
- 1976: W.M. Smart: Textbook on Spherical Astronomy (6th ed.) ... (previous) ... (next): Chapter $\text {II}$. The Celestial Sphere: $19$. Declination and hour angle.
- 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): declination (dec)
- 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): equatorial coordinate system
- 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): declination (dec)
- 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): equatorial coordinate system