Glasgow College of Nautical Studies Faculty of Maritime Studies
AMPLITUDES
Amplitude refers to the bearing of a celestial body when it is rising or setting above the Rational Horizon, i.e. True Altitude = 00° 00.0'.
NOTE An Amplitude of the sun is taken when the lower limb of the body is 1 semi-diameter above the visible horizon, allowing for the corrections this is when the sun has a True Alt 0°
An amplitude is the angle measured from the East / West line, to the body.
The Amplitude is named E or W depending on whether the body is rising or setting.
The Amplitude is named N or S depending on the Declination of the body.
Sine Amplitude = Sine Declination
Cosine Latitude
AZIMUTHS
The Azimuth is calculated using A, B, C Tables or by calculator it is a function of:
· Latitude,
· Declination,
· LHA.
A = Tan Lat Named opposite to Lat except when Hour Angle between 90° and 270°
Tan LHA
B = Tan Dec Always named same as Declination.
Sin LHA
C = A ± B + if A and B are the same names.
- if A and B are different names.
C is named the same as the greater component.
Tan Azimuth = 1
C x Cos Lat
Azimuth is named by C and LHA LHA 0° to 180° Body is to the West of the observer
LHA 180° to 360° Body is to the East of the observer
dariusz.lipinski