Semi-sextile: the 30° minor aspect in a birth chart

A semi-sextile is an aspect between two planets that stand 30° apart along the ecliptic. It is one twelfth of the circle and half a sextile, hence the name. The semi-sextile is not one of the five Ptolemaic aspects. It counts as a minor aspect: it is used with a small orb and read as a refinement of the picture the major aspects have already drawn.

Geometry: neighbouring signs

Each sign of the zodiac spans 30°, so a classic semi-sextile links planets in neighbouring signs: Aries and Taurus, Leo and Virgo, Capricorn and Aquarius. Neighbouring signs have nothing in common. The element differs, because elements alternate around the circle: fire, earth, air, water. The modality differs too: a cardinal sign is followed by a fixed one, and that by a mutable one. Even the polarity is opposite, since masculine and feminine signs take turns.

So in a semi-sextile two planets work through signs that share no common language. What separates it from the quincunx, where the signs also share nothing, is distance: the planets sit close together, and one of them stands in the sign the other has just left or is about to enter.

Why tradition did not see it

Hellenistic astrology defined aspects primarily by sign. Signs two, three, four and six signs apart "see" each other: that gives the sextile, square, trine and opposition. Neighbouring signs, and signs five apart (150°), were said not to see each other. Modern translations call this state aversion.

For an ancient astrologer, then, a semi-sextile was not a weak aspect but the absence of an aspect. The 30° angle entered practice later, together with the other minor aspects, once aspects came to be measured by the exact angle between planets rather than by sign. Johannes Kepler proposed several of the new angles in the early 17th century, and in 20th-century astrology the semi-sextile settled into the aspect tables of most software.

The orb of a semi-sextile

Like other minor aspects, the semi-sextile gets a narrow orb: usually 1-2°, up to 2-3° with the Sun or Moon. A wider margin makes the aspect too common. Every planet sits next to some neighbouring sign, and with a 4-5° orb each chart would hold several semi-sextiles that say nothing about the person.

Most astrologers therefore ignore a semi-sextile wider than 2° and consider one within 1° worth attention.

Out-of-sign semi-sextiles

Some semi-sextiles have an angle close to 30° while the signs are not neighbours. A planet at 29° Aries and one at 1° Gemini are 32° apart, and with a 2° orb that is still a semi-sextile. Yet Aries and Gemini form a sextile by sign, not an aversion. The opposite case is more common: two planets at either end of one sign, say 0° and 29° Leo, are formally in semi-sextile while living in the same sign.

Such out-of-sign aspects are read more cautiously than classic ones. The geometry is there, but the difference between the signs, which gives the semi-sextile its character, is missing or of another kind.

How to read a semi-sextile

Modern astrologers describe the semi-sextile in different ways. Some treat it as a weak harmonious aspect, a relative of the sextile. Others see light friction in it, because the signs are neighbours yet strangers. Most often it is described as a link that asks for gradual adjustment: the two functions do not clash openly, but neither do they support each other without effort.

A semi-sextile is read through the same layers as any aspect:

• Planets. Which functions are linked. A semi-sextile of the Sun to Saturn speaks of will and structure; one of Venus to Mars, of desire and action.
• Signs. How each planet acts. The signs are neighbours, so the pair always crosses a change of element, modality and polarity.
• Exactness. The smaller the orb, the greater the weight. A semi-sextile within 0°20′ can matter more than a wide square.

A minor aspect rarely changes the overall reading of a chart. It works best as a refinement: it can explain why two planets that share no major aspect still work together in a person.

Example: the semi-sextile in Donald Trump's chart

In Donald Trump's chart the Sun is at 22°55′ Gemini and Saturn at 23°48′ Cancer. The angle between them is about 30°53′, an orb of 0°53′. Gemini is a mutable air sign, Cancer a cardinal water sign: a classic semi-sextile across neighbouring signs that differ in element, modality and polarity.

There is no major aspect between the Sun and Saturn in this chart, and without minor aspects the two would easily be read as unconnected. The semi-sextile shows a thin thread between will and structure, which tradition would describe as a need to reconcile one's self-image with the demands of circumstance. This describes a link between two functions of the chart, not a judgement of the person.

How to find a semi-sextile in your own chart

The aspect tables of most software list only the major aspects, so minor ones often have to be found by hand. The simplest way is to write the planets' positions in absolute degrees: Aries covers 0-30°, Taurus 30-60°, Gemini 60-90° and so on to Pisces at 330-360°. The Sun at 22°55′ Gemini becomes 82°55′, Saturn at 23°48′ Cancer becomes 113°48′.

Then, for each pair of planets, subtract the smaller number from the larger. If the result is over 180°, subtract it from 360°. Compare the angle with 30°: a difference of no more than 1-2° means a semi-sextile. There is also a quicker check: planets in neighbouring signs at almost the same degree within the sign, such as 12° Virgo and 12° Libra, are always in semi-sextile.

Semi-sextiles in configurations

The semi-sextile rarely takes part in well-known figures. The closest case is a stellium: planets gathered in two neighbouring signs are often joined by semi-sextiles. Another case involves the quincunx: the semi-sextile and the quincunx add up to 180°, so if one planet opposes another and a third is in semi-sextile to one of them, it will be in quincunx to the other.

In celebrity charts

The tightest examples among the published charts.

• Kylian Mbappé: Venus semi-sextile Uranus, orb 0°00′
• Beyoncé: Sun semi-sextile Jupiter, orb 0°01′
• Toni Kroos: Mars semi-sextile Neptune, orb 0°03′

Calculate your chart