Synastry inter-aspects: which contacts to read first

An inter-aspect is an angle between a planet in one person's chart and a planet or point in another person's chart. It is calculated exactly like a natal aspect: take two positions on the ecliptic, measure the distance between them and see whether it falls close to 0°, 60°, 90°, 120° or 180°. The one difference shapes the whole method. Two charts together produce dozens of such angles, and most of the work in synastry is choosing the few that actually say something.

How an inter-aspect is calculated

Both charts are laid on the same wheel. If partner A has the Sun at 14°20′ Taurus and partner B has Saturn at 12°00′ Aquarius, the two points are 92°20′ apart: a square with an orb of 2°20′. Geometrically nothing distinguishes it from a natal square. The reading is different, though. It no longer describes friction inside one person but the way a function in one person meets a function in the other. Here B's Saturn stands at a right angle to A's Sun, which in a relationship is read as an area where B limits, tests or gives shape to A's self-expression.

The aspect types are the same as in a natal chart: the conjunction, sextile, square, trine and opposition. Minor aspects are rarely used in synastry, because the major ones already supply more than enough material.

Which points to look at first

A full list of inter-aspects between two charts easily runs to several dozen. So astrologers work by priority, starting with the points that describe the core of each person and moving out to the background.

• The luminaries. Each partner's Sun and Moon. Contacts between one person's Sun and the other's Moon are traditionally treated as the most noticeable in a couple.
• The Ascendant. It describes how a person comes across and how others first experience them. A partner's planet aspecting your Ascendant is felt early, often from the first meetings. It can only be used when the birth time is reliable.
• Venus and Mars. Venus describes what a person enjoys and how they show affection, Mars how they want and how they act. Their contacts with the luminaries and with each other are the first thing read in a romantic pairing.
• Saturn. It shows where a couple feels duty, permanence and sometimes pressure. One partner's Saturn aspecting the other's luminaries and personal planets is traditionally seen as what holds a relationship together over time.

Mercury and Jupiter come next. Uranus, Neptune and Pluto sit in almost the same place for two people of a similar age, so their contacts with each other's slow planets say little about this particular couple. What matters is a tight aspect from one of them to the other person's luminaries, Ascendant or Venus.

Orbs in synastry

Most astrologers use tighter orbs in synastry than in a natal chart. The reason is arithmetic: two charts produce several times as many pairs, and with natal allowances almost every planet ends up with several contacts. The table in the orbs article is still the reference point, but you work from the lower end of each range or below it.

The luminaries and the Ascendant usually keep a wider allowance than the other planets, for the same reasons as in a natal chart. The example below allows up to 6° for conjunctions, oppositions, trines and squares involving the luminaries or the Ascendant, up to 5° for their sextiles and up to 4° for everything else. That convention is only for this example. An aspect within 1-2° stands out under any approach.

Two directions and mutual aspects

An aspect between A's Mars and B's Sun is not the same thing as an aspect between B's Mars and A's Sun. They are different pairs of planets, and each describes its own side of the relationship: in the first, A's drive acts on B's sense of self; in the second it runs the other way. That is why synastry is written out in two passes: A's planets to B's points, then B's planets to A's points.

When the same pair of functions appears in both directions, the contact is called mutual. A's Sun trine B's Moon together with A's Moon in aspect to B's Sun would be one. A mutual contact works both ways and usually carries more weight than a one-sided one. A one-sided aspect is not weaker in itself, but it describes an asymmetry: one partner feels it more than the other.

Repeating themes

A single inter-aspect rarely defines the picture. A theme repeated by several different aspects is far more reliable. If B's Saturn squares A's Sun, A's Saturn conjoins B's Moon and B's Saturn also opposes A's Mars, Saturn has come up three times and from both sides. That theme deserves to be described first, even if none of its aspects is the tightest in the list.

Repetition can also gather on a single point. When several aspects land on one of a partner's planets, that planet becomes the focal point of the synastry, much like the apex of a pattern in a natal chart. Inter-aspects can form patterns of their own as well: an opposition between two people's planets plus a third planet square to both gives a T-square spread across two charts.

A worked example: partners A and B

Partner A: Sun 14°20′ Taurus, Moon 3°10′ Cancer, Venus 27°45′ Pisces, Mars 9°05′ Leo, Saturn 22°30′ Capricorn, Ascendant 11°40′ Libra. Partner B: Sun 10°15′ Scorpio, Moon 16°50′ Capricorn, Venus 5°30′ Leo, Mars 25°10′ Aries, Saturn 12°00′ Aquarius, Ascendant 7°25′ Aquarius.

Within the orbs set above there are twelve aspects:

Aspect	Orb
A's Ascendant trine B's Saturn	0°20′
A's Mars square B's Sun	1°10′
A's Mars opposite B's Ascendant	1°40′
A's Sun square B's Saturn	2°20′
A's Sun trine B's Moon	2°30′
A's Saturn square B's Mars	2°40′
A's Mars opposite B's Saturn	2°55′
A's Mars conjunct B's Venus	3°35′
A's Sun opposite B's Sun	4°05′
A's Ascendant trine B's Ascendant	4°15′
A's Ascendant square B's Moon	5°10′
A's Saturn conjunct B's Moon	5°40′

The first thing to notice is that A's Mars takes part in four aspects, which makes it the focal point. It opposes B's Saturn and Ascendant, which sit close together in Aquarius in B's chart, squares B's Sun and conjoins B's Venus. B's Sun is also natally square B's own Saturn (orb 1°45′), so A's Mars, B's Saturn and B's Sun form a cross-chart T-square with B's Sun at the apex.

Second, Saturn repeats from both sides. B's Saturn touches A's Sun and Mars, and A's Saturn touches B's Moon and Mars. Each Saturn aspects the other person's Mars and one of their luminaries, so this is a mutual theme even though it is built from different aspects.

Third, A's Moon and B's Sun are 127°05′ apart, a trine with an orb of 7°05′. With natal allowances for the luminaries this would complete a mutual Sun-Moon trine; with synastry orbs it drops out. Here the choice of orb changes the conclusion.

The reading would start with A's Mars and the Saturn theme, not with the tightest aspect in the table. A's Ascendant trine B's Saturn at 0°20′ matters, but it stands on its own and nothing reinforces it.

How not to drown in aspects

A working order that keeps synastry manageable:

1. Tighten the orbs and drop aspects between slow planets.
2. List the aspects to the luminaries, Ascendant, Venus, Mars and Saturn, one direction at a time.
3. Mark any planet that receives three or more aspects.
4. Find the repeating themes and the mutual pairs.
5. Only then look at isolated tight aspects that belong to no theme.

Aspects to the Ascendant and MC need an accurate birth time for both people. The same applies, even more strongly, to the next layer of synastry, house overlays.

Compare two charts