Synastry and Composite Charts: The Difference

Synastry and Composite ChartsThe synastry chart describes the chemistry between two people and defines how the couple affects one another. It is generally descriptive of how two people make each other feel when they are interacting. Both Synastry and Composite charts can be analysed for all types of relationships, such as parent-child, husband-wife, siblings, a business partnership or friendship.

We observe feelings of affection, communication, sexual compatibility and/or attraction through synastry which signifies an interchange of the cross-energies between two individuals. We could describe the synastry between two people as the dialogue of a play, with the disparate tones, contents and resonances of the lines spoken.


  • The chemistry of a couple is an important aspect in relationship analysis showing how the relationship connects and reveals why we have such a fascinatingly powerful and magnetic response to one person and not another. A synastry chart is also useful for sorting out and connecting the bits of information the couple presents.
  • Through assessing the synastry chart we can instinctively weigh the pros and cons of their respective similarities and differences, often unintegrated parts of the self, unmask themselves through a partner, and this is often the case with the square or opposition in our chart, then it usually shows through our partner, lover, marriage partner, child, or parent. A synastry chart is all about how we click and connect with others; the aspects between our planets represent degrees of attraction, and how we connect emotionally, mentally and physically.
  • A composite chart combines two natal charts from a mysterious fusion of two into a manifold one. The composite chart takes the same planet from each chart and marks the midway point, and this forms a new Sun sign and house position for the relationship, along with a new Mercury, Venus and Mars, etc. The composite chart is very similar to a natal chart and describes something new emerging. The new chart has its own purpose, needs, mode of operating and even growth and cycles reflected by the transits to the composite. We can also compare our own natal chart to the relationship’s to determine how this partnership affects us.
  • The Sun in the composite describes the identity of the relationship and the focus of the bond and the whole chart identifies the challenges in the relationship, describing the qualities of the relationship itself. We may also observe where the composite Sun falls in our own personal horoscope and this will tell us where the life-force and purpose of the relationship will animate and light up a particular area in our natal chart.
  • Astrologer Liz Greene describes the composite chart as having a curious fated feeling, and both people must learn to live with certain patterns of energies, which is constellated whenever they interact. This third wheel in the relationship which we call the composite, defines some of the roadblocks that exist in the relationship itself, and these kinds of things are usually more accurately described within the composite than through a synastry chart which mostly reveals our interaction.


  • Studying composite charts is fascinating and many astrologers have different takes on how this new fusion and synthesis of planets relate to a couple. For instance, one astrologer would not consider that two quiet and shy individuals can become more confident and outgoing in one another’s presence. Other astrologers, however, maintain the view that this can indeed happen. Personally, I believe the latter is true and that we do act differently with other people, and sometimes we act markedly different in a relationship than when we are acting independently of the bond.
  • A composite chart also reflects the general atmosphere we create around us as a couple. Planets rising in the composite greatly colour how others perceive the relationship. We can interpret a composite chart in exactly the same way as we would read an individual chart. The signs in the composite chart describe the basic temperament of the relationship and the planets are the dynamic forces, and the houses describe the spheres of life through which the planets express themselves.
  • A Sun –Saturn aspect in the composite chart would reflect roadblocks constantly occurring in the couple’s joint goals, purpose and the forming of an identity, but these events are outside of our personal control. It could happen through such a situation in the couple 's life that there may be certain boundaries they can never cross, restrictions imposed upon them. This makes the relationship feel limited at times and even frustrating, but the separate individual charts will describe how such a couple copes with these inbuilt limitations in the relationship.
Here is an example of a Sun-Neptune aspect in the composite chart by Liz Greene which may help towards understanding how to read aspects in a composite chart:
“Most powerful is a composite in which the Sun makes a strong aspect to Neptune, for then the essential goals and meaning of the relationship are coloured by Neptune’s longing for fusion and flight from the pain of the mortal world. Such relationships are often based on shared spiritual or artistic commitment. If this kind of container can be provided, darker Neptunian elements may not prove too great a problem. Where no such container exists, the relationship may require some form of abnegation which, with or without the consent of the individuals, denies the possibility of it being sustained in the world of form. Sometimes the relationship comes into being through shared guilt, or an obligation such as unplanned pregnancy. “ By Liz Greene, Neptune and the Quest for Redemption


Julie O'Mahoney

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