limb(redirected from catacrotic limb)
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limb(lim) The apparent edge of the Sun, Moon, or a planet, or any other celestial body with a detectable disk.
a flat metal ring divided by lines into equal parts of circumference (for example, degrees or minutes). It is the most important part of instruments used in measuring angles (in astronomy, geodesy, physics, and so on); it gives a reading of the magnitude of the angle. The scale units of a limb are read by means of a vernier or a micrometric microscope.