What is "angular distance"

Angular \An"gu*lar\, a. [L. angularis, fr. angulus angle, corner. See Angle.]

1. Relating to an angle or to angles; having an angle or angles; forming an angle or corner; sharp-cornered; pointed; as, an angular figure.

2. Measured by an angle; as, angular distance.

3. Fig.: Lean; lank; raw-boned; ungraceful; sharp and stiff in character; as, remarkably angular in his habits and appearance; an angular female.

   Angular aperture, Angular distance. See Aperture, Distance.

   Angular motion, the motion of a body about a fixed point or fixed axis, as of a planet or pendulum. It is equal to the angle passed over at the point or axis by a line drawn to the body.

   Angular point, the point at which the sides of the angle meet; the vertex.

   Angular velocity, the ratio of anuglar motion to the time employed in describing.

Distance \Dis"tance\, n. [F. distance, L. distantia.]

1. The space between two objects; the length of a line, especially the shortest line joining two points or things that are separate; measure of separation in place.

   Every particle attracts every other with a force . . . inversely proportioned to the square of the distance.
   --Sir I. Newton.

2. Remoteness of place; a remote place.

   Easily managed from a distance.
   --W. Irving.

   'T is distance lends enchantment to the view.
   --T. Campbell.

   [He] waits at distance till he hears from Cato.
   --Addison.

3. (Racing) A space marked out in the last part of a race course.

   The horse that ran the whole field out of distance.
   --L'Estrange.

   Note: In trotting matches under the rules of the American Association, the distance varies with the conditions of the race, being 80 yards in races of mile heats, best two in three, and 150 yards in races of two-mile heats. At that distance from the winning post is placed the distance post. If any horse has not reached this distance post before the first horse in that heat has reached the winning post, such horse is distanced, and disqualified for running again during that race.

4. (Mil.) Relative space, between troops in ranks, measured from front to rear; -- contrasted with interval, which is measured from right to left. ``Distance between companies in close column is twelve yards.''
   --Farrow.

5. Space between two antagonists in fencing.
   --Shak.

6. (Painting) The part of a picture which contains the representation of those objects which are the farthest away, esp. in a landscape.

   Note: In a picture, the

   Middle distance is the central portion between the foreground and the distance or the extreme distance. In a perspective drawing, the

   Point of distance is the point where the visual rays meet.

7. Ideal disjunction; discrepancy; contrariety.
   --Locke.

8. Length or interval of time; period, past or future, between two eras or events.

   Ten years' distance between one and the other.
   --Prior.

   The writings of Euclid at the distance of two thousand years.
   --Playfair.

9. The remoteness or reserve which respect requires; hence, respect; ceremoniousness.

   I hope your modesty Will know what distance to the crown is due.
   --Dryden.

   'T is by respect and distance that authority is upheld.
   --Atterbury.

10. A withholding of intimacy; alienation; coldness; disagreement; variance; restraint; reserve.

    Setting them [factions] at distance, or at least distrust amongst themselves.
    --Bacon.

    On the part of Heaven, Now alienated, distance and distaste.
    --Milton.

11. Remoteness in succession or relation; as, the distance between a descendant and his ancestor.

12. (Mus.) The interval between two notes; as, the distance of a fourth or seventh.

    Angular distance, the distance made at the eye by lines drawn from the eye to two objects.

    Lunar distance. See under Lunar.

    North polar distance (Astron.), the distance on the heavens of a heavenly body from the north pole. It is the complement of the declination.

    Zenith distance (Astron.), the arc on the heavens from a heavenly body to the zenith of the observer. It is the complement of the altitude.

    To keep one's distance, to stand aloof; to refrain from familiarity.

    If a man makes me keep my distance, the comfort is he keeps his at the same time.
    --Swift.

n. the angular separation between two objects as perceived by an observer; "he recorded angular distances between the stars"

In mathematics (in particular geometry and trigonometry) and all natural sciences (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 the angle between the two directions originating from the observer and pointing towards these two objects.