AMPLITUDE

AMPLITUDE of the Range of a Projectile, is the horizontal Line subtending the Path in which it moved. See PROJECTILE.
Amplitude, in Astronomy, an Arch of the Horizon, intercepted between the true East or West Point thereof, and the Centre of the Sun, or a Star at its rising or setting. See HORIZON, RISING, SETTING, &c.
Amplitude is of two Kinds; Eastern or Ortive; and Western, or Occiduous. Eastern, or Rising Amplitude, Amplitudo Ortiva, is the Distance between the Point wherein the Star rises, and the true Point of East, wherein the Equator and Horizon intersect. See EAST.
Some call it Eastern, or Ortive Latitude. See LATITUDE.
Western, or Setting Amplitude, Amplitude Occidua, is the Distance between the Point wherein the Star sets, and the true Point of West in the Equinoctial. See WEST.
The Eastern and Western Amplitude, are also called Northern, and Southern, when in the Northern and Southern side of the Horizon. The Complement of the Eastern or Western Amplitude to a Quadrant, is called the Azimuth. See AZIMUTH.
To find the Sun's or a Star’s Amplitude, either rising or setting, by the Globe. See GLOBE.
To find the Sun’s Amplitude, trigonometrically; having the Latitude, and the Sun's Declination given.
Say, As the Co-sine of the Latitude is to Radius, so is the Sine of the present Declination to the Sine of the Amplitude.
Suppose, e.g., the Latitude 15° 30’, and the Declination 11° 50'; Then to the Ar.co. of
the Co-fine of 50° 30’ : 0,2058503
Add the Sine of : 9,3118926
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Sum is the Sine of : 9,5177429
which is the Amplitude requir’d.



Magnetical Amplitude, is an Arch of the Horizon, contained between the Sun, at his rising, and the East or West Point of the Compass; or, it is the Difference of the Rising or Setting of the Sun, from the East or West Points of the Compass. See COMPASS, RISING, SETTING, etc. It is found by observing the Sun at his rising or setting, by an Amplitude Compass. If the Compass have no Variation, the Magnetical Amplitude will be the same as the true one.

AMPLITUDE