Traditionally, the Synastry Chart or Comparison Chart, is the most widely used relationship chart. The natal planetary positions of both partners are shown in one chart. The interpretation is based mainly on the aspects between the planets in one of the birth charts in relation to positions in the other, as well as on the house placements, i.e. which houses are 'set in motion' by natal planets of the partner. Inevitably, any interpretation must analyse and compare the individual charts as well, particularly in regard to the Sun, Venus and the 7th house, as well as element balance. In this manner, the Synastry Chart or Comparison Chart depicts an analytic approach, with a lot of attention given to single aspects.
The second important method used in the analysis of relationships, is the Composite Chart or midpoint chart. For each pair of planets the mid-point is calculated, these are then shown as a chart drawing. In a sense this shows us the essential structure of the relationship. Composite charts are abstract, computed constellations, and do not represent a real astronomical situation. For this reason, I (A.T.) was rather sceptical towards these 'unreal' horoscopes to begin with. However, after having been surprised by a very succinct description of several relationships, I now believe a combination of the composite method with an analytic method should be practised.
In the ASTRO*INTELLIGENCE Relationship Horoscope, our computerized relationship analysis created with Liz Greene, both techniques are used, as well as a comparison between both birth charts and the composite. There are two methods used to determine the Composite Ascendant: Either one can use the latitude of a place of reference, or one uses the mid-point of both Ascendants. We offer chart drawings for both methods. For composite charts for more than two people, see Multiple Composite, (Type 68 and 681). Unfortunately, this very interesting area has not yet been much explored.
Since the Composite Chart shows a symbolic constellation, rather than a real one, many prognostic techniques (transits, Solar returns, directions) cannot be applied, or only with reserve. As a complement to the Composite Chart, which is based on a physical mid-point, the Davison Relationship Chart was developed. The Davison Chart is computed for a mid-point in time, in relation to a geographical mid-point or 'middle point' and drawn like a birth chart. The interpretation is similar to that of a Composite Chart. The outer planets and the Meridian are usually similarly positioned in both chart types, since any time taken as a mean between both birth times will show these to be more or less in the middle between both positions. The important difference is that the Davison Relationship Chart is based on a real point in time, thus enabling one to use all the known techniques such as Solar returns, transits, progressions and other directions in order to explore a development in time.
We should not neglect to consider the rich tradition of Horary Charts while discussing relational astrology. As we know, a horoscope can describe any event, as well the birth of a human child. The horoscope is a symbolic representation of the quality of a moment in time, affecting all things coming into being at that time. The first encounter of a couple, or the hour of marriage, are such moments, possibly a separation or divorce as well. Charts depicting events such as these are just like a natal chart, calculated for the time and place of an event. Order Type 2.AT or any other type natal chart drawing.