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abstraction > mathematical concept > number > quantity > angle > parallax > horizontal parallax
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horizontal parallax comparison table
Subject is a kind of has definition
parallaxangleThe difference in apparent direction of an object as seen from two different locations; conversely, the angle at the object that is subtended by the line joining two designated points. Geocentric (diurnal) parallax is the difference in direction between a topocentric observation and a hypothetical geocentric observation. Heliocentric or annual parallax is the difference between hypothetical geocentric and heliocentric observations; it is the angle subtended at the observed object by the semi-major axis of the Earth's orbit. First trigonometric parallax was obtained in 1838. (eee also horizontal parallax.)
horizontal parallaxparallaxThe difference between the topocentric and geocentric positions of an object, when the object is on the astronomical horizon.

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