Pasachoff, Jay M. Hopkins Observatory, Williams College, Williamstown, Massachusetts.
- Additional Readings
The point in the sky directly above an observer. If the observer is at a pole, then the observer's zenith is a celestial pole; but for observers at midlatitudes the zenith is a point in the sky that corresponds to a changing right ascension but a constant declination as the sky rotates overhead. The point directly below the observer is the observer's nadir, and is 180° in longitude and in latitude from the observer's zenith.
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