|| Starpath online classroom || Celestial Navigation Glossary || Glossary Index || Home ||

A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z

magnitude A logarithmic scale for the brightness of celestial bodies. The smaller the magnitude number, the brighter the object, so negative magnitudes mean very bright objects. There are 20 magnitude-one stars (the brightest stars), about 70 magnitude-two stars (2 to 3 times fainter than the first group), about 200 magnitude-three stars (about 6 times fainter than the first group), and about 500 magnitude-four stars (about 16 times fainter than the bright guys). On a reasonably clear night in Seattle one can see magnitude-four stars. In navigation we use almost exclusively first and second magnitude stars. The planets are typically brighter than the stars by as much as 1 to 4 magnitudes. The magnitudes of planets are listed on the Nautical Almanac daily pages, but to find star magnitudes you must look in the back of the Nautical Almanac, in the special star lists. See The Star Finder Book for details and a convenient brightness table. See also Planets. The Star index from the nautical almanac is also included in Pub 249. Vol 1.

[close window]