de·scen·sion /dɪˈsɛnʧən/
  De·scen·sion n.  The act of going downward; descent; falling or sinking; declension; degradation.
  Oblique descension Astron., the degree or arc of the equator which descends, with a celestial object, below the horizon of an oblique sphere.
  Right descension, the degree or arc of the equator which descends below the horizon of a right sphere at the same time with the object. [Obs.]
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