Amplitude of an observed heavenly body
Amplitude (of an observed heavenly body)
The angle subtended at the observer's zenith between two great circles of the celestial sphere perpendicular to the observer's horizon, one of which passes through the observed body and the other through the east and west points of the observer's horizon.
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM