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amplitude

A convenient term (though little used in routine navigation) that describes the bearing of any celestial body on the horizon (when rising or setting). It is the number of degrees away from due east or west that a body rises or sets. It is labeled North or South according to its location relative to east or west. If a body has an amplitude of 30 N, it rises 30 north of east (at 060 T) and sets 30 north of west (at 300 T). The name (N or S) of the amplitude is always the same as that of the declination. With a calculator, amplitude can be found from:

Sin(Amp) = Sin(dec) / Cos(Lat).

Our Emergency Navigation book has a simple graphic solution to this equation for amplitude.

Abbreviation:  A or Amp

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