Introduction to Spherical Astronomy: p. 11

Term: declination

The stars on the celestial sphere are like cities on the globe. Cities are located on the globe using latitude and longitude. Longitude says how far the city is east or west along the Earth's equator; latitude says how far a city is north or south of the Earth's equator.

Declination is like latitude. It reports how far a star is from the celestial equator. To find the declination of a star follow an hour circle "straight down" from the star to the celestial equator. The angle from the star to the celestial equator along the hour circle is the star's declination.