Synastry is when two charts are super imposed on one another (see below); you need both parties date of birth, time and place to compare with one another. Synastry tells you the energies activated in each partner; what emotions are dredged up, where you come together and where you are miles apart. Looking at a couples synastry cannot tell you if 2 individuals will end up together. I’ve looked at great synastry that had the depths of an ocean, but you must consider free will. I believe free will and the natal promise are interwoven. Before peeking at both charts you may want to asses who they are as individuals, look at the ascendant (the house of self), the descendent (the house of partnerships) to see who they are as an individual and who and what they would like in a partner. Below: Example A. Has Aquarius rising, Leo on the descendent, indicating this personal belongs to the world, a humanitarian and forward thinking that tends to attract showy partners that may be possessive. Example B. Is a Scorpio rising with Taurus on the descendent, Possessive, secretive with a desire for a traditional partner, perhaps a homebody. Example A is ruled by Uranus the planet of freedom and the unexpected. Person B descendent is ruled by Taurus the slowest moving earth sign which tends to be set in its ways. Although they may like one another (suns are sextile) and activate feelings of ease around one another (Venus sextile moon), lust (mars sextile Venus) and intense passion (Venus opposition Pluto) in one another. This may not be what they see for their life . Example A has Aquarius rising and is comfortable with Uranian themes. But take a look at Example B Uranus is tucked away in the 12th house, hidden from the world. Example 1 has only one earth planet where as Example 2 has an earth planet on the 7th house cusp. Also look to see where is each person’s sun located, where is their focus in life. It may be complicated for 2 individuals to come together when Examples 1. Sun is in the 5th house of fun and leisure and Example 2 Sun is in the 6th house of work and daily activities. Also look at how is the chart shaped? Are most of the planets below the horizon in houses 1-6 or are they above in houses 7-12. People with majority of their planets below the horizon experience events internally, process things below the surface where as a person with planets above the horizon are constantly seeking to make connections outside of themselves. Once you establish who each person is as an individual then you can proceed to compare them and the energies they have toward one another. You will want to look and take into careful consideration the interactions of the Sun, Moon, Mars, Venus also known as the personal planets to one anothers and which houses the planets fall into.
Composite charts take the mid points of each person, it is a combined horoscope and can be read much like a natal chart. It is the combined energy of the couple. Did you ever date someone and that puts you in touch with your adventurous side, perhaps you would ski or white river rafting when you are together, but maybe with someone else you stay at home and make fondue and play scrabble. Everyone we meet introduces us to certain facets of life and every relationship is different we concentrate on different things, we want different things from different people. So here is the same Sample as above only this time I’m looking at the composite chart. The synastry is very Plutonian, a lot of love/hate sex and control issues going on so hypothetically speaking if those 2 fictions people did decide to merge this would be there composite chart.
Example A and Example B Composite Chart, where as they natally they have Aquarius and Scorpio rising, the Composite Rising Sign in Capricorn appears serious and appearance oriented. The ruler of Capricorn is Saturn, Saturn is placed in the 7th house…Saturn in the 7th usually indicates one of 2 things: 1. This relationship will have an issue getting started 2. Once it does get off the ground it is written in stone, binding. Assuming they are together you can reach the conclusion as a couple they spend a great deal of time working out together, spending time with their favorite pets (sun in the 6th house), they have a healthy sex life (mars conjunct venus) and live in a home beautifully decorated (venus in the 4th house), they experience great highs and lows together and expressing feelings is a VERY high priority here as the moon is placed in the 7th house. Something may be odd about them as a unit, people did not expect them to come together Uranus is in the 10th house of reputation. The planet of the unexpected, maybe they end up together due to some event beyond either of their control. Composite pluto in the 9th house and the fact that it is trining the sun means this is a couple with great strength that can work together or at odds to brings great changes to one another as well as the world around them.
Synastry is how you feel and connect to one another. Composite how you will explore your relationship once the connection is solidifie.