- (Also called variation.) In terrestrial magnetism, at any given location, the angle between the geographic meridian and the magnetic meridian; that is, the angle between true north and magnetic north.
Declination is either "east" or "west" according as the compass needle points to the east or west of the geographic meridian. Lines of constant declination are called isogonic lines and that of zero declination is called the agonic line.
- In astronomy, the angular distance between any given celestial body and the celestial equator, measured along a great circle (hour circle) passing through the celestial poles; thus, the astronomical analog of geographic latitude.
Declination is positive for positions north of the equator and negative for positions south of the equator. Declination and right ascension are the coordinates used in positional astronomy.
Copyright 2022 American Meteorological Society (AMS). For permission to reuse any portion of this work, please contact email@example.com. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act (17 U.S. Code § 107) or that satisfies the conditions specified in Section 108 of the U.S.Copyright Act (17 USC § 108) does not require AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, require written permission or a license from AMS. Additional details are provided in the AMS Copyright Policy statement.