#sight.optical_instrument  a optical instrument for aiding the eye in aiming, as on a firearm or surveying instrument
  supertype:  #optical_instrument__opticalinstrument  an instrument designed to aid vision
  subtype:  #bombsight  #gunsight
  part of:  #firearm  #surveying_instrument
  part:  #eyepiece__ocular  combination of lenses at the viewing end of optical instruments
     part:  #reticle__graticule  a network of fine lines, dots, cross hairs, or wires in the focal plane of the eyepiece of an optical instrument
        part:  #cross_hair__crosshair__cross_wire__crosswire  either of two fine mutually perpendicular lines that cross in the focus plane of an optical instrument and are use for sighting or calibration; "he had the target in his cross hairs"

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