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< Heliocentric >

The Sun as a center. The science of Astrology is largely based on geocentric observations, since it treats of cosmic forces as perceived or received by an inhabitant of the Earth. Some authorities believe that heliocentric considerations may contribute added testimony of importance, for which reason the heliocentric longitudes 2nd latitudes of the planets are to be found in some ephemerides. In reducing heliocentric positions to geocentric terms, a mean orbit is employed wherein the planets are presumed to move in a circle at a uniform rate. This is corrected by an equation to centre, based upon the eccentricity of the orbit - its departure from a true circle. Having determined the true position in the orbit, a further equation, improperly called parallax, is employed to reduce the position to its geocentric longitude.