The orbits of most of the planets in the solar system lie in approximately the same geometric plane, which is why an astrological chart using only a two-dimensional representation rather than one with three dimensions is drawn. There is, nevertheless, a variation in the tilt or angle of these orbits, so at any given time most of the planets are either north or south of the celestial equator (the plane described by projecting Earth's equator against the background of the stars). This variation is measured in degrees of declination. Two planets are parallel when they are on the same side of the celestial equator and have the same degree of declination. Planets with the same declination are said to have a relationship similar to a conjunction.
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