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Celestial navigation, also called astronomical navigation, is the art and science of finding one’s geographic position through astronomical observations, in most cases by measuring altitudes of celestial bodies sun, moon, planets, or stars.
An observer watching the night sky without knowing anything about geography and astronomy might spontaneously get the impression of being on a horizontal plane located at the center of a huge hollow sphere with the celestial bodies attached to its inner surface. This naive concept of a spherical universe has probably been in existence since the beginning of mankind. Later, astronomers of the ancient world (Ptolemy et al.) developed it to a high degree of perfection. Still today, spherical astronomy is fundamental to celestial navigation since the navigator, like the astronomers of old, measures apparent positions of bodies in the sky without knowing their absolute positions in space