Semi-sextile aspect: 30° between neighboring signs

Ptolemy does not count the semi-sextile among the aspects. In the Tetrabiblos (book I, chapter 16), he classes neighboring signs among the “disjunct” or “alien” signs, with none of the four aspect relationships. His image is striking: two adjacent signs are as it were turned away from one another and, though they are two, they enclose the angle of only one.

Geometry bears this out: two neighboring signs share neither element, nor modality, nor gender. Aries and Taurus, masculine cardinal Fire and feminine fixed Earth, have nothing in common but their border. The Skyscript glossary notes that in classical times the semi-sextile was often held too weak to produce a noticeable effect without support.

William Lilly comes across it in the ephemerides. In Christian Astrology (1647), on page 32 of book I, he explains how to read their columns: the symbol SS marks a semi-sextile, an aspect of 30°, and the example for the day is a semi-sextile of Mars and Mercury. He places it among the aspects that “one Kepler, a learned man” has added, with the quintile, the tredecile, the biquintile and the quincunx, and warns that he mentions them only so the reader can grasp their meaning on finding them.

In book III, though, Lilly does use it, in the directions of an English merchant's nativity, where the Part of Fortune reaches the semi-sextile of a planet several times, of Mercury, the Moon or Mars. Attributions to Kepler vary from one source to another; what is certain is that the aspect is a 17th-century addition to Ptolemy's list.

Two bodies in semi-sextile neither oppose each other nor merge. They are in contact, one sign apart, and that contact calls for a little work of integration between two functions that do not quite speak the same language. The legend of the aspect table in your report sums it up in two words: quiet support.

With the Sun semi-sextile the Moon, will and the emotional world sit slightly out of step, each in a different sign, and the person learns to tune them to each other in small touches. Always read the semi-sextile as a secondary nuance, never as the axis of a chart.

In your birth chart, the orb of the semi-sextile is 2°: two bodies 28° to 32° apart are in semi-sextile. It is the narrowest tolerance in AstralPro's whole table, and the same for all bodies. An aspect this discreet can only be read close to exactness.

To spot it, look at the neighboring signs: a body at 10° Aries is in semi-sextile to any body placed between 8° and 12° Taurus, or between 8° and 12° Pisces. Outside that four-degree window, the grid keeps nothing.

It is treated like the other minors: present in the complete natal grid, in the blue of the harmonious aspects, absent from the wheel and from the Book's table, which is reserved for majors. It rarely makes it into the aspects the chapters discuss, where the majors come first.

The directions of the English merchant's nativity, at the end of book III of Christian Astrology, show how Lilly read the aspect. The Part of Fortune at the semi-sextile of Mercury “makes the Native to peruse some notes and accounts.” Mars at the semi-sextile of Mercury seems to promise, by means of a Mercurial man or some attorney, quickness and speed in obtaining what is owed to him.

The register is modest: everyday business, errands, accounts. None of these directions announces a turning point. Lilly uses the semi-sextile for light effects, which fits the narrow tolerance it is given today.

Ptolemy treats signs one sign apart and five signs apart together: both are disjunct. Geometry links them too. 30° and 150° add up to 180°: a body in semi-sextile to a point is in quincunx to the opposite point. On the Ascendant-Descendant axis or the axis of the Nodes, the grid writes only one of the two contacts, the one that touches the Ascendant or the North Node.

Yet the two aspects do not carry the same weight in AstralPro. The quincunx gets a 5° orb, the semi-sextile 2°. The first links two signs that everything separates and that have to adjust; the second, two neighbors that touch without resembling each other, and your report's legend calls it quiet support rather than tension. When it is applying, the support is building; separating, it is already in place.

Camille Morel, AstralPro's sample chart (fictional data), has no semi-sextile: her grid of 40 aspects does not carry a single line of one. It is not for lack of neighboring planets. Her Jupiter, at 0°50' Scorpio, and her North Node, at 3°00' Sagittarius, are 32°10' apart: the gap exceeds 30° by 2°10', ten minutes of arc beyond the tolerance. Mars, at 3°38' Sagittarius, is 32°48' from Jupiter, further still. On the other side, Mars is 27°08' from Venus and 27°01' from Mercury: 2°52' and 2°59' from the semi-sextile, outside the tolerance as well. If the semi-sextile had the semi-square's 3° tolerance, these two lines would have appeared; with 2°, they do not.

Purely as a hypothesis, had Jupiter been a few minutes further into Scorpio, the line Jupiter semi-sextile North Node would have entered the grid at its place by orb, in blue. Its Direction column would carry a dash, Jupiter and the North Node both being slow bodies. It would have been neither drawn on the wheel nor discussed by a chapter.