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Synastry (Chart Comparison)

(religion, spiritualism, and occult)

Synastry, or chart comparison, is the practice of superimposing two or more horoscopes and examining their interactions. Synastry is an especially popular technique for evaluating romantic relationships, but it can also be used for illuminating business partnerships, parent-child interactions, and so forth. The basic idea of chart comparison is very old. In Hindu astrology, for example, the practice of comparing charts to determine marital compatibility is quite ancient. In the Western tradition, Ptolemy mentions synastry in his Tetrabiblos, the single most influential astrological treatise in European history. Even the famous Swiss psychiatrist Carl Jung used chart comparison in his work with married couples.

Traditional chart comparison focuses on the aspects between key planets. Thus, if the natal Mercury (planet of communication) of one individual is conjunct the Mercury of the other, the relationship will be characterized by easy communication between the two. Mentally, they will see eye to eye on many issues. In romantic relationships, it is especially interesting to note how Venus (the planet of relating) and Mars (the planet of passion) are aspected. A close conjunction between one person’s Mars and the other person’s Venus, for instance, is traditionally viewed as a powerful romantic-sexual aspect.

Among astrologers who accept the notion of reincarnation, Saturn is viewed as the planetary ruler of karma (one’s ledger of debts and dues from previous lifetimes). Where the Saturn of a person with whom one is in a close relationship falls in one’s natal chart indicates something about the nature of one’s karmic tie. For example, if a close relative’s Saturn is located in one’s second house (the house of money and possessions) when the charts are superimposed, there is some sort of financial karma from past lifetimes. If neither person’s Saturn is strongly aspected in a comparison, there is no significant karmic tie, and the relationship will usually be transitory.


Brau, Jean-Louis, Helen Weaver, and Allan Edmans. Larousse Encyclopedia of Astrology. New York: New American Library, 1980.
Sakoian, Frances, and Louis S. Acker. The Astrology of Human Relationships. New York: Harper & Row, 1976.