The specification of the location of anobject or measurement within a reference coordinate system. The position isusually expressed as a set of values corresponding to the location along aset of ortho
gonal axes together with the date/time of the observation.
The convention for measuring angles on the sky in astronomy (abbreviated as PA). It is the direction of an imaginary arrow in the sky, measured from north through east: 0° = north, 90° = east, 180° =
south, and so on to 359° and back to 0°. Applied to a binary system it is the direction of a secondary body or feature from a primary, measured in the system.