Position angle a hypothetical binary star with a PA of 135 degrees, that means an imaginary line in the eyepiece drawn from the north celestial pole to the primary (P) would be offset from the secondary (S) such that the NCP-P-S angle would be 135 degrees. When graphing visual binary orbits, the NCP line is traditionally drawn downward—that is, with north at bottom—and PA is measured counterclockwise. Also the direction of the proper motion can for example be given by its position angle. The definition of position angle is also applied to extended objects like galaxies, where it refers to the angle
Angle "AOC", then The measure of the angle "AOC" is the sum of the measure of angle AOB and the measure of angle "BOC". In this postulate it does not matter in which unit the angle is measured as long as each angle is measured in the same unit. Units used to represent angles are listed below in descending magnitude order. Of these units, the "degree" and the "radian" are by far the most commonly used. Angles expressed in radians are dimensionless for the purposes of dimensional analysis. Most units of angular measurement are defined such that one "turn" (i.e. one