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Synastry Aspects
Sun synastry aspects
Moon synastry aspects
Mercury synastry aspects
Venus synastry aspects
Mars synastry aspects

House Overlays
Points in the first house
Points in the second house
Points in the third house
Points in the fourth house
Points in the fifth house
Points in the sixth house
Points in the seventh house
Points in the eighth house
Points in the ninth house
Points in the tenth house
Points in the eleventh house
Points in the twelfth house

Synastry is the study of relationships by comparing two horoscope charts (for relationships between more than two people, see group analysis). By comparing the relative position of planets and houses and the interaspects between charts, astrologers attempt to predict the way two people will tend to interact with each other. Synastry is the most common method used in relationship astrology. Another common method is the use of composite charts to study how two people behave as a couple.

Natal promise

Each person is unique in their expectations of a relationship. In order for two people to satisfy each other there needs to be some compatibility in the way they approach relationships. Therefore most astrologers will first make a thorough study of each person's birth chart. For example, an individual with Leo on the seventh house cusp will have an entirely different approach to committed relationships than someone with a Mercury-ruled Virgo seventh house cusp. In order to love another, a person must first be able to love and nurture themselves, which can be seen in the natal aspects to Venus and the Moon. People can and do change, however, and a person with natural low self-esteem may overcome those tendencies through awareness and dedication to self-growth. Other areas to consider are past wounds (Chiron), obsessions (Pluto) and repressed issues (possibly indicated by the Twelfth house and Saturn). Projection refers to the psychological tendency to "project" our own buried feelings, fears or traits onto other people. Projection can be observed in the natal chart at the Descendant, the seventh house and oppositions to planets such as Saturn, Moon or Venus1.

House overlays

In order to compare the two horoscopes a synastry chart (most likely a bi-wheel) is constructed. By looking at the interaspects between the planets (and possibly other points) and by looking at where the planets and houses of one chart fall in the other chart the astrologer can learn a great deal about how the two people are likely to react to each other. As with all chart interpretation, there may be some factors which conflict with other factors, and it is not always clear which characteristic will become dominant. Furthermore, individuals may choose to express an energy in different ways. For example, a tight square aspect between Mars and Venus in two charts may cause strife and hurt feelings or it could be an indicator of great passion. Synastry can reveal a lot about how energy flows or blocks between two people, but how they handle that ease or stress is dependent on the psychology of the people involved.


Most people who have a synastry analysis done are interested in compatibility, that is they want to know if they can have a happy and stable relationship with the other person. Compatibility indicators include:

  • Conjunctions, parallels, trines and sextiles of Sun, Moon, Mercury, Venus, Jupiter or Ascendant between charts (e.g. Sun conjunct Moon)
  • Conjunctions, trines, sextiles and parallels between one person's Venus and the other's Mars
  • Trines and sextiles from one person's Sun, Moon or Jupiter to the other's Mars
  • Trines and sextiles between the personal planets and outer planets (e.g. Sun trine Pluto
  • Any aspect with Venus and Jupiter (e.g. Venus opposition Venus)
  • Similar signs and genders emphasized between the charts (e.g. both partners have a water Moon or one has an Aries Ascendant while the other has an Aries Moon).
  • Mirrored aspects (e.g. both partners have Moon in aspect to the other's Pluto or both have a bucket shaped chart)
  • A hard aspect (especially conjunction) from a personal planet of one person to the Sun/Moon midpoint of the other.

Basic compatibility is indicated by the Sun/Moon aspects. Romantic love and attraction is indicated by Venus/Mars aspects. Moon aspects indicate feelings and needs, Venus aspects love and values and Sun aspects will and authority. Amiability and general success are indicated by Jupiter aspects. Mars (energy and drive) works best in soft aspect with the yin planets Venus, Moon and Jupiter.

Longevity (which is not the same thing as compatibility!) is indicated by aspects to Saturn from personal planets. Adoration is indicated by aspects to Neptune. Excitement is indicated by aspects to Uranus. Intensity is indicated by aspects to Pluto. In all cases, these should be trines, sextiles or possibly parallels to avoid working against the relationship.

In some cases a hard aspect is better than no aspect. For example, it is probably better to have Moon opposition Moon between charts than to have no strong Moon contacts, but it is a difficult aspect that causes some struggle. Hard aspects (including the conjunction) to Mars, Pluto, Saturn and Uranus are mostly trouble, though, and hard aspects to Neptune often indicate unreasonable expectations and eventual disillusionment.

These are indicators for the potential for a good relationship for most people, however there are occasionally couples who prove the exception to these "rules" and carry on a successful partnership with little or none of these aspects. Conversely, there are couples who have several of these factors but never really get the relationship started. Part of the reason for this is probably due to the psychological state of the people involved (and this should be visible in the natal chart and progressions). But one could also say that individual will (or perhaps faith) is the deciding factor in relationships, or in any other major endeavor. Therefore synastry can be reliably used to indicate areas of trouble or ease in a relationship, but it should not be the primary factor in deciding whether a relationship is viable.

People who like pain

Unfortunately, people often mistake passion and compulsion for compatibility. This is particularly true for people who grew up in a dysfunctional family, and can be seen in the natal charts (see Natal promise). As a result, we have many people who tend to find compatible people boring and instead seek out difficult relationships. This is a matter of choice, but it can be heartbreaking to watch a loved one fall into the same negative patterns over and over again. Spiritual and psychological counseling can help to overcome these behavior patterns. A good technique to use to judge whether a relationship is appropriate is to imagine that it is a dearly loved friend or child in your situation instead of yourself. Then think of what you might say to him or her.

Red flags in a synastry chart include hard aspects and imbalance in the house overlays. If person X has mostly yin houses and planets activated by person Y, then X will feel dependent on Y and easily hurt by Y. This is okay if Y has the same thing, but if Y has mostly yang houses and planets activated it will cause Y to be more indifferent to X, causing X pain and insecurity2. Hard Pluto aspects can create a feeling of obsession about the relationship that is hard to ignore. Saturn conjunct the Sun can make the bond feel indissoluble, but can also make the Sun person feel trapped. Uranus lends an electric excitement that has nothing to do with true intimacy. Neptune can feel very beautiful, but can also cause love to be blind to everything from alcoholism to outright abuse. Any of these planetary influences in small measure or easy aspect are manageable, and may even add some extra spice to the relationship. If there are mostly squares and oppositions, the relationship will require consistent mutual effort to maintain.

Karmic relationships

Certain aspects between charts may indicate psychological or spiritual work that needs to be done (or for those who believe in it, past life karma that has to be dealt with in this lifetime). These aspects appear in relationships that have a fated feeling to them. The relationship usually results in growth through the process of changing negative life patterns or beliefs. Karmic aspects do not indicate compatibility. In fact, the relationship could be very brief, only long enough to confront the repetition of a negative pattern and to make a decision about it. The idea of "soulmates" is very prevalent in astrology, and karmic aspects are often used as indicators of whether someone might be your soulmate. Whether or not soulmates exist or have karmic ties to us, having a lot of karmic aspects to another person does not make them your soulmate. It does not even make them necessarily likeable. But it does create a magnetic attraction (not necessarily a romantic one). Aspects that are considered karmic include:

  • Conjunctions (or possibly parallels) from one person's personal planet to the other's Saturn, Nodes or Chiron. Some astrologers only use the South Node as it indicates the past whereas the North Node indicates the future, however both nodes lend a fated feeling to the relationship. Trines and oppositions to Saturn or Chiron may be considered as well, but conjunctions are more significant.
  • Conjunctions (or parallels) between the Moon and Pluto or Neptune (some also consider Uranus)
  • Conjunctions or oppositions from one person's personal planet or Ascendant to the other's vertex
  • Conjunctions from personal planets to the IC

See Also


  1. Cafe Astrology article on synastry
  2. Cafe astrology - house overlays