DECLINATION, in astronomy, the dis tance of any celestial object from the equinoctial, either northward or south ward. It is either true or apparent, ac cording as the real or apparent place of the object is considered. A great circle is supposed to pass through the two poles, and through the centre of every star. This circle is called a circle of de clination. The arc of this circle included between the star and the equator Mea sures the declination of the star. The declination of a star then is itkperpendi cular distance from the equator. It is north or south, according as the star is situated on the north or south side of the equator. All the stars situated in the same parallel of the equator have, of course, the same declination. The decli nation then marks the situations of a star north or south from the equator. Pre cision requires still another circle, from which their distance, east or west, may be marked, in order to give the real place. The circle of declination, which passes through that point of the equator called the vernal equinoctial point, has been chosen for that purpose. The distance of the circle of declination of a given star from that point, measured on the equator, or the arc of the equator inw eluded between the vernal equinox and the circle of declination of the star, is called its right ascension. If we know the
declination and the right ascension of a star, we know its precise situation in the heavens.
The declination of any star may be easily found by observing the following rule : Take the meridian altitude of the star, at any place where the latitude is known ; the complement of this is the zenith distance, and is called north or south, as the star is north or south at the time of observation. Then, I. When the latitude of the place and zenith distance of the star are of different kinds, namely, one north and the other south, their dif. ference will be the declination, and it is of the same kind with the latitude, when that is the greatest of the two, otherwise it is of the contrary kind.-2. If the lati tude and the zenith distance are of the same kind, i. e. both north or both south, their sum is the declination ; and it is of the same kind with the latitude. See GLOBES, use of ,f