One of the most fascinating topics to study in astrology is synastry, or the comparison of two people's charts to determine their likely compatibility and relationship. Synastry is the astrological answer as to why we are strongly drawn to certain people, why we feel these deep, often inexplicable, attractions.
Though I'm far from perfecting this art, I've discovered there are key factors in charts that tend to indicate powerful connections between people, and can point to possible soulmate relationships. The following is a discussion of these potent astrological aspects.
The angles of the chart marked by the Ascendant-Descendant axis (first and seventh house cusps) and the Midheaven-Nadir axis (tenth and fourth house cusps) are the most personally defining points in a chart because they are drawn from the exact birthtime and place. A strong connection occurs when a planet, Node (see paragraph below) or angle of one chart is conjunct the partner's Ascendant, Descendant, Midheaven or Nadir. I look for at least one of these angle contacts within a reasonable orb of six or seven degrees; but the tighter the orb (within three degrees of exact) the more powerful the connection.
Another thing to look for is a sharing of the angular signs (signs that rule the angular houses: Ascendant/first house, Nadir/fourth house, the Descendant/seventh house, and the Midheaven/tenth house). For example, let's say a person has Libra/Aries on the Ascendant-Descendant axis and Cancer/Capricorn on the Midheaven/Nadir axis; and their partner has Sagittarius/Gemini on the Ascendant axis and Libra/Aries on the Midheaven axis. They have Libra/Aries in common. I notice this happens quite often in marriages, between parents and children, and also among siblings.
The Nodes of the Moon — which also form an axis in the natal chart — are considered to be of special significance to our psychological and spiritual evolution. They have a very powerful role in synastry. Many astrologers think that the Nodes carry past life implications, and therefore indicate soulmate connections. If a planet or angle in one chart conjuncts or forms a tight square to their partner's North or South Node, the relationship can feel extremely binding, a strong sense of belonging together, especially if the Sun, Moon, or an angle of the chart is also involved.
One person's Sun, Moon or Ascendant in the sign of the partner's Sun, Moon, or Ascendant provides a sense of familiarity and common ground in which to relate. A conjunction here (within six degrees of exact) is an especially powerful force. I find that one person's Moon in tight conjunction or opposition to the other person's Sun, Moon or Ascendant is the most powerful. The Moon is particularly important in relationships because it represents basic needs and one's emotional nature.
Saturn, the dreaded planet of depression, restriction, and fear, surprisingly plays a very important role in synastry. Saturn provides structure and purpose to the relationship. I like to see at least one tight Saturn aspect: one person's Saturn aspecting one of the partner's personal planets or an angle (and this includes the hard aspects as well: conjunction, square, opposition, along with the more welcome trine). Saturn provides the glue, and a relationship needs Saturn to grow. It will not usually stand the test of time without it. Too much Saturn influence, however, can be a problem because of the control and manipulation the Saturn person can exert over their partner.
I've just started Noel Tyl's Master's Certification course and he puts great emphasis on theSun/Moon midpoint in regard to relationships. It's no wonder as this point represents the integration of the polarity between the masculine (represented by the Sun) and feminine (the Moon) — the yin and yang of the psyche. When a personal planet (especially Sun, Moon, Venus) or the Ascendant makes a hard aspect, in particular a tight conjunction, to their partner's Sun/Moon Midpoint this relationship will be extremely important.
Another very interesting thing to note is the timing of a couple's meeting. Check the transits to and progressions of both charts for this date. Look at the eclipse tables and note the sign and degree of those nearest to their meeting date. You will find, with startling regularity, that a couple's most powerful synastry point was being activated at the time they met.