circle of perpetual apparition
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circle of perpetual apparition[′sər·kəl əv pər′pech·ə·wəl ap·ə′rish·ən]
That circle of the celestial sphere, centered on the polar axis and having a polar distance from the elevated pole approximately equal to the latitude of the observer, within which celestial bodies do not set.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.