parallactic inequality

parallactic inequality

A minor periodic term in the Moon's motion that results from the gravitational attraction of the Sun and causes the Moon to be ahead at first quarter and to lag behind at last quarter (see phases, lunar). The inequality can be used to calculate solar parallax. See also evection; variation.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

parallactic inequality

[¦par·ə¦lak·tik ‚in·i′kwäl·əd·ē]

(astronomy)

parallactic equation

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.