ANN's Daily Aero-Term (03.20.09): Almucantar (The Aero-News Network)

Aero-Terms! An almucantar (also called a "parallel of altitude") is a circle on the celestial sphere that is parallel to the horizon. It consists of all points at a given altitude - if two points are on the same almucantar, they have the same altitude.

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by Yahoo Parachute News