Angle and History

The septile arises from the sevenfold division of the circle and belongs to the family of harmonic aspects developed in twentieth-century Western astrology rather than to the seventeenth-century reform of Johannes Kepler, whose new aspects were built from figures, the pentagon and the octagon, that can be constructed with compass and straightedge and that correspond to consonant musical ratios; seven offers no equivalent construction, which is very likely why it plays no part in Kepler's own scheme. The aspect's currency in modern practice owes most to John Addey (1920 to 1982), whose Harmonics in Astrology of 1976 argued for reading the chart through whichever numerical divisions proved statistically significant, including the seventh and the ninth, rather than restricting analysis to aspects that fit evenly into signs. It has no standard glyph and no dedicated place in the Unicode Standard; it is written with the letter S or with the digit seven, and because the true angle carries an irrational remainder, most software rounds it for display while noting that the underlying figure never divides the circle exactly.

Addey worked from within British astrology in the decades after the Second World War, and his push to treat the whole zodiac as one wave that could be analysed into numbered harmonics, on an analogy with the way a musical tone can be broken into a fundamental and its overtones, is the specific intellectual move that let the septile and several other previously unused divisions into serious modern practice at once.