Note:  Do not rely on this information. It is very old.


Amplitude, in astronomy, the distance of a heavenly body from the east or west points, at the instant of its rising or setting. The amplitude of a star is always the same; but that of the sun varies from zero at the equinoxes (q.v.) to a maximum at midsummer and midwinter. In oscillatory motion of a particle, the amplitude of vibration is the greatest distance of the particle from its mean position.