Septile

The septile is an aspect of about fifty-one and three-sevenths degrees, formed by dividing the circle into seven equal parts. Because seven does not divide three hundred and sixty into a whole number, the septile falls at an irrational angle, and this sets it apart from the aspects built on simpler fractions. It is a minor aspect, given a very narrow orb, and it was not among the classical Ptolemaic set; interest in it grew with the harmonic astrology of the twentieth century. The tradition that uses it reads the septile as a relation touched by fate, compulsion, or inspiration, an irrational, otherworldly quality fitting its irrational angle, often linked to creativity and the sense of destiny. These are the interpretive conventions of the astrological tradition for this angular relation, one of the subtler aspects derived from dividing the circle by seven.

Because seven has no factor in common with the other small harmonics that generate the recognised aspects, one, two, three, four and six, the septile family stands apart from the semi-sextile, semi-square, sesqui-quadrate and biquintile, all of which are built from divisors already present in Ptolemy's five. The septile belongs to the wider revival of harmonic aspect theory that follows Kepler's Harmonices Mundi of 1619, though Kepler's own attention fell mainly on the fifth harmonic; twentieth century harmonic astrologers, prominently John Addey, did the systematic work of extending the approach to the seventh and other primes. Because 360 divided by seven never resolves to a whole number of degrees, software and older ephemeris-based practitioners can differ by a small fraction of a degree in where they place it, an ambiguity the aspects built on whole-number divisions do not share.

A seventh of three hundred and sixty degrees is fifty one degrees, twenty five minutes and about forty three seconds, and it never resolves into a whole number. That single fact governs everything about the septile. It cannot be found by counting signs, because seven does not divide twelve. It cannot be drawn on a traditional chart wheel, which is built from twelves. It can only be measured, and only once measurement is precise enough to be worth doing.

This is why the septile has no classical history. It appears in the modern period among writers extending Kepler's harmonic argument, and it belongs entirely to the school that treats an aspect as a division of the circle rather than as a relation between signs. Even within that school it is treated as marginal, and the orb given to it is very tight, often under a degree, since a wider one would run into the semi-square on one side and the sextile on the other.

The interpretations attached to it lean on the symbolism of seven rather than on any observational record: compulsion, fatedness, the irrational, the sense of being carried by something not chosen. Those readings should be identified as what they are, an argument from number symbolism, because there is no body of traditional testimony behind them to appeal to. The septile is best described as a genuine geometric division of the circle whose astrological meaning is asserted rather than inherited, and a reader is entitled to know that before it is used to explain anything.

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.