- Angular distance
In
mathematics (in particulargeometry andtrigonometry ) and allnatural science s (including astronomy, geophysics, etc), the angular distance (angular separation, apparent distance, or apparent separation) between two point objects, as observed from a location different from either of these objects, is the size of theangle between the two directions originating from the observer and pointing towards these two objects. Angular distance (or separation) is thus synonymous to angle itself, but is meant to suggest the (often large or unknown) linear "distance" between these objects (for instance stars, as they are observed from Earth).Measurement
Since the angular distance (or separation) is conceptually identical to an angle, all three are measured in the same units, such as degrees or
radian s, using instruments such asgoniometer s or optical instruments specially designed to point in well-defined directions and record the corresponding angles (such atelescope s).Equation
In order to calculate the angular distance in
arcsecond forbinary star system ,extrasolar planet s, solar system objects and otherastronomical object s, we useorbital distance (semi-major axis ) in AU divided bystellar distance inparsec s.:heta = frac {a}{D}
See also
*
Angular mil
*Grad (angle)
*Hour angle
*Central angle
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