Before revision: Sight is defined as the observation of the altitude, and sometimes also the azimuth, of a celestial body for a line of position; or the data obtained by such observation.The American Practical Navigator (2002) Nowadays sight reduction uses the equation of the circle of equal altitude to calculate the altitude of the celestial body, .
After revision: Sight is defined as the observation of the altitude, and sometimes also the azimuth, of a celestial body for a line of position; or the data obtained by such observation.The American Practical Navigator (2002) The mathematical basis of sight reductin is the circle of equal altitude .