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
Inner regular measure from within by compact sets." Some authors use the term tight as a synonym for inner regular. This use of the term is closely related to tightness of a family of measures, since a finite measure "μ" is inner regular if and only if, for all "ε" > 0, there is some compact subset "K" of "X" such that "μ"("X" \ "K") < "ε". This is precisely the condition that the singleton collection of measures {"μ"} is tight. When the real line R is given its usual Euclidean topology, However, if the topology on R is changed, then these measures