Dexter

Applied to an aspect which is computed backward, against the order of the Signs; in which the aspected body is elevated above the aspecting body. If this appears opposite to what you sense it should be, remember that Ptolemy, who originated the term, knew only apparent motion - that of the daily motion of the heavens because of the Earth's rotation; therefore the one ahead, was on the right hand - dexter; and the one behind, was on the left hand - sinister. There is some controversy as to which are the stronger, although the ancients gave preference to the dexter. Today, some differentiation can be had by application of the Doppler effect noted in spectroscopy, wherein the ray from a body whose position is becoming increasingly distant is displaced toward the red end of the spectrum, while with lessening distance the displacement is toward the violet end. Since the dexter aspect is forming as the result of increasing distance it would show a displacement toward the red end, which would tend to introduce into the aspect a measure of Mars energy; while the sinister aspect, forming as the result of decreasing distance, would show a displacement toward the violet end, which would tend to introduce into the aspect a measure of Venus or Jupiter geniality. From this one might infer that the relative desirability of a dexter and sinister aspect is somewhat dependent upon the nature of the planets that are involved.