Introduction to Relationship Astrology 2:
Synastry (subjective compatibility factors)

– written by Philip Graves Jan 30 2003
– reformatted for WordPress, June 9th, 2016



In this second part of the article, comprising the third and fourth overall subsections, we are going to consider the astrological factors connecting the birth charts of two particular people, which are known as synastric factors. These linking factors largely determine the potentialities for the quality, extent and areas of manifestation of the interactions between the two people concerned, independently of their objective natures and needs as individual people (covered in the first part). They are therefore often known as the subjective factors influencing the relationship.

It is worth remembering that synastric factors are not evenly and mutually felt by the two people involved in the same way, since they consist of the factors belonging to one person’s chart being conditioned and affected, for better or worse, by those in the other person’s chart with which they are connected; and the other person in turn will feel the factors in his / her chart being conditioned by those in the first chart with which they are connected. It is precisely because for each person there is a different set of factors in the other person’s chart acting as agents of altered behaviour and perception, that neither person experiences the interaction in the same light; and what may for one person be a very positive linkage may in the reverse direction feel like a burden, or go by almost unnoticed.


3. Synastric house overlays

This term refers to connections between the two people’s birth charts whereby the factors in one are placed (overlain) in the houses of the other, and vice versa.

Draw up a vertical list for the first person of the zodiacal signs and degrees where each of his / her twelve natal house cusps are situated. Then look to the second person’s luminaries, planets and lunar nodes at birth, and place them within the houses of the first person, according to which house they would fall into by their zodiacal sign and degree position if they were in the first person’s birth chart. Remember that if they are within three degrees of the cusp of the next house after the one they are in, they may effectively be considered equally powerful in that house.

Then draw up a like vertical list of the second person’s house cusp signs and degrees, and fit the first person’s luminaries, planets and lunar nodes within it.

This combined information yields 24 synastric factors: twelve showing the houses of the first person’s chart into which the second person’s significant non-house-cusp factors (two luminaries, eight planets, two nodes) fall, and twelve showing the inverse.

Just as in a birth chart, the house occupied synastrically by any chart factor in one person’s chart will show the area of life in which it is inclined to be manifested when it is given expression in the interactions with the second person. E. W. Neville talks of planets being ‘captured’ in the other person’s houses, as though the house concerned had somehow stolen them away and preset the nature of their expression in accordance with its particular filtering effect.

In synastry, the house placements of the Moon and Venus are of particular importance to emotional and physical relationships, while that of the Sun influences the Sun person’s sense of his / her own identity as reflected in interaction with the house person.

Any planets in the other person’s 1st house will also accent the qualities of the planet concerned in the behavior, manner and apparent sense of identity of the planetary person, when he / she interacts with the house person.

The house placement of Mercury will naturally influence the scope of the Mercury person’s verbal communication, and that of Mars the direction in which the Mars person’s energies will be expressed.

Any planets in the other person’s 5th house will influence the planetary person’s inclinations towards and perceptions of feelings of love and fun, according to the nature of the planet concerned.

The Moon, Venus or Jupiter in the 5th are extremely favorable influences for the flow of positive emotion.

Any planets in the other person’s 7th house will influence the planetary person’s inclinations towards treating the house person in a partnership context, and perceptions of this situation.

The Sun, Moon, Venus or Jupiter in the 7th house favor marriage or a long-term partnership.

Any planets in the other person’s 8th house will connect the planetary principle concerned for the planetary person to the darker, more forbidden and powerful undercurrents of the house person’s life-force, and are therefore strongly associated with sexual attraction, colored by the nature of the planet concerned.

Luminaries, personal planets, and especially benefics in the 1st, 5th and 7th houses are generally very favorable indications for any relationship.

Saturn will experience feelings of inhibition or restriction but also disciplined application in whatever area of life, in connection with the other person, is indicated by its synastric house placement.

Saturn in the more practical houses such as the 2nd, 4th, 6th and 10th is easier to handle than in the more emotional and personal houses, where a love relationship is concerned.


4. Synastric interplanetary aspects

This term refers to interplanetary aspects connecting the two people’s birth charts, whereby factors in one chart are said to be in synastric aspect to those in the other.

Draw up an X-Y aspect grid (similar to the one suggested for the birth chart in my ‘Introduction to aspects’ article), with vertical columns for the first person’s Sun, Moon, planets, North Node, Ascendant and Midheaven (the latter two only if the birth time is known to be accurate) along the x-axis, and horizontal rows for the second person’s equivalent factors along the y-axis. Be sure to include the sign and degree position (preferably to the nearest decimal point of one degree) of all factors when labelling the columns and rows. It is very helpful when drawing up aspect grids to be in the practice of drawing and instantly recognising glyphs (astrological symbols) as shorthand for the full wording of the planets and signs, since it saves a lot of space.

You will now have a two-dimensional grid full of empty boxes that represent the connections between the sign and degree positions of the luminaries, planets, nodes, Ascendant and Midheaven in one chart with those of all the equivalent factors in the other. Use a calculator to determine the number of degrees and tenths of a degree separating every factor listed in the first chart with every factor listed (in turn) in the second, and fill in the number into the appropriate box in the grid in each case.

Then determine which of these numbers of degrees of angular separation qualify as significant aspects, and for those which do write down the glyph for the aspect concerned (if known) in the same box, or alternatively simply write out in word form beneath the grid the full name of the aspect between Person A’s factor concerned and Person B’s factor concerned. It is important to keep a note of whose factor is which, since in synastry, as noted earlier, the experience is not equal for the two individuals.

The recommended orbs of allowance for the major synastric aspects are more limited than those for the birth chart, with the conjunction being capped at 6º, the opposition at 5º, the square at 4.5º, the trine at 4º, the sextile at 2.7º, the semisquare and sesquiquadrate at 1.8º, and the semisextile and quincunx at 1.5º. It is questionable that any more minor aspects whose recommended orb is lower than 1½º should be used at all. Typically, you will still find around 20-30 synastric aspects to interpret. There are many factors in relationship astrology; and when working out the aspects alone, with twice as many planets involved as in a single birth chart there is a potential for a very large number of factors, so it is essential to restrict analysis to those which will be likely to be felt as significant and omit from the equation those tiny influences sure to be drowned out by the greater smog of the rest and consideration of which would only obscure the greater overall picture.

There are some interplanetary aspects that are particularly helpful to harmony and love, and to physical attraction, and others that can be particularly problematic. See below for a quick description from experience and observations of the more common suspects. Conjunctions and easy aspects (sextiles and trines) will feel quite different from the harsher interactions associated with squares, oppositions, semisquares, sesquiquadrates, semisextiles and quincunxes. It is worth referring to the quick guide to the effects of the different types of aspects in my ‘Introduction to Aspects’ article.

Because human needs from relationships are complex, including the resolution of internal conflicts and complexes, indicated by the birth chart or caused by childhood experiences, it is not necessarily the case that people will be attracted to partners with whom they share a large number of easy synastric aspects. While trines, sextiles and benefic conjunctions may promote friendship and easy rapport, they may equally induce laziness, complacency, and a lack of interest in pursuing the relationship to a deeper level. The needs for different qualitative characteristics in a relationship will vary widely from one individual to another; and very often people are drawn to relationships wherein the potentials are complicated and difficult.

Aspects from Sun or the Ascendant to Venus generate or condition feelings of love and harmony, and when the aspects are easy or conjunctions they are major positive influences upon any relationship.

Aspects from Sun or the Ascendant to the Moon connect the ego identity and general life force (Sun) or socially projected countenance (Ascendant) of the first person with the emotional nature of the second, and are also very favorable bonding influences unless the type of aspect is a hard one.

Aspects from the Sun to the Sun or Ascendant show basic qualities of harmony or disharmony in the interaction between the individuals’ respective personalities.

Aspects from the Moon to Venus create a sublimely emotional bond, linking the general emotional nature of one person with the love nature of the other.

Aspects from Venus to Venus and from the Moon to the Moon also accentuate and condition the emotional interaction between the individuals, but with regard to like emotional principles. Hard aspects between these like principles may cause emotional tension and conflict.

Aspects from the Sun or the Ascendant to Mars create a distinctly energetic interaction between the two people, usually manifest on a level of physical activity in some form, but in certain circumstances may cause arguments, the assertive energy or Mars clashing with the ego of the Sun.

Aspects from Mars to Mars are even more energetic, with a greater risk of clashes where hard aspects are concerned.

Aspects from the Moon to Mars are generally very favorable, connecting the emotional realms and instincts of the Moon person with the energetic self-assertion of the Mars person.

Aspects from Venus to Mars are particularly associated with physical and sexual attraction, since they link the Venus principle of beauty and love with the Mars one of physical energy; and in this instance all types of aspects are favorable, including squares and oppositions, whose more conflicting inherent energies make for a magnetically appealing challenge to be grounded in this arena of life.

Aspects from the Moon or Venus to Neptune are generally very pleasant emotional influences, sensitising the interaction to the more subtle, romantic and otherwise unseen realms of feeling and awareness, though with the potential for self-delusion particularly applying to the Moon or Venus person in receipt of the Neptune contact to his / her emotional principle concerned.

Aspects from the Moon or Venus to Pluto add a dark intensity and power to the emotional sphere influenced by whichever of the first two factors applies. Relationships with these contacts often are characterised by a compulsive quality.

All aspects to Mercury impact upon communication, especially verbal communication.

All contacts to Jupiter will promote optimism, bonhomie and humor in the areas affected by the factor aspected by Jupiter.

All aspects to Saturn act as restrictive, dampening, but often stabilising and grounding influences upon the interaction. Sextiles and trines, and conjunctions to the benefics, are a lot easier to handle than the harsher aspects, and conjunctions to the malefics.

The overall balance of Saturn contacts can make or break any relationship. A relationship with little in the way of synastric aspects to Saturn tends to feel deficient in stability and structure; it may be light and easy, but there can be too little to hold it together. An excess of Saturn contacts to the personal planets, conversely, makes for misery, taking the joy out of the interaction, and, where the Moon or Venus are involved, tending to deaden the emotional expression, though also providing a stable context for it.

Saturn conjunctions and hard aspects to the Sun, Mars, Uranus or Pluto are generally very unwelcome, troubling influences.

Conjunctions and hard aspects from the Sun or Mars to Pluto are potentially equally problematic, inducing disruptive or obsessive energies.

Contacts between Uranus and the Sun, Ascendant, Mars or Jupiter introduce a certain unpredictability into the interaction, and a risk of sudden separation and other upsetting changes.

Harsh contacts to Uranus, like those to Saturn, are among the most unwelcome synastric influences on a relationship, their ultimate tendency, beyond the introduction of a certain degree of welcome excitement, seeming to be to keep people apart from each other.

Aspects from the Moon or Venus to Uranus introduce an element of excitement and unpredictability into an emotional relationship, which can be positive; but where the hard aspects are concerned can tend to cause emotional separations, or at least to be very unsettling.

Aspects to the Moon’s Nodes, especially conjunctions (and their concurrent oppositions to the opposite node) often create a feeling of strong karmic bonding between people, in accordance with the planets involved and the nature of the aspect. There can be a sense with North Node conjunctions of mutual assistance towards evolutionary development, while with South Node conjunctions one of a more comfortable, unchallenging, familiar and reassuring feel to the connection.

It is worth remembering that the experiencing of any synastric linkage of a factor in one’s own chart with one in the other person’s, although to a certain extent operating by itself, will tie into the whole configuration of natal aspects to the factor concerned in one’s own birth chart, and be experienced as a modifying deviation from one’s experiences as an individual in isolation. It is not possible to completely separate the experience of a synastric aspect from the lens onto it of the person experiencing it, this lens being shaped by his or her innate nature.


Continue To Part Three of Three…

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