The Difference Between The Relationship Charts
This is my attempt to differentiate between the relationship charts that i currently know of, based on how they are calculated or erected.
This post is not a reference on how to calculate each chart, and is 100% my opinion.
Calculated: This chart is erected by overlaying person A's natal chart on person B's chart, and then calculating the aspects that are formed between the respective planets and points. For e.g. the aspect that person A's sun makes to person B's sun, and the same for the moon and ascendant and so on.
Meaning: Because of this, the chart symbolizes how easily (good aspects) or how difficult (bad aspects) the different functions/energies for one person's planets meet or flow or interact with the other.
The Synastry Chart uses aspects between like planets or points to tell how person A's energy meets/clashes with person B's energy; where they interact.
Calculated: This chart is erected by finding the midpoint between the respective planets and points of each person's natal chart, and then a new chart is erected with the midpoint position of the planets being the new position for the planets in the composite chart. For e.g. if person A's moon is in 7° Aries, and person B's moon is in 3° Gemini, then the midpoint between the moons, i.e. 15° Taurus, is the position for the composite moon.
Meaning: Because of this, the chart symbolizes how the two individual planets or points merge (i.e. composite) into a new planet/point or each person into a new whole.
The Composite Chart uses midpoints between like planets/points to tell how person A's energy blends with person B's energy; where they compromise.
Calculated: This chart is erected by finding the midpoints between the times of birth and the places of birth of the two persons. This creates actual natal data with an actual time and place of birth.
Meaning: Because of this, this chart symbolizes how the two original people created a new potential/event (or person) from their own individual whole energies.
The Davison Chart uses midpoints between the birth dates and place to tell what happens after/ the effects when person A and B's energies meet and merge; where they create potential.
Calculated: This chart is erected using the midpoints of the birth data on the Davison Chart, and the birth data of another person that is a part of the first Davison Chart.
Meaning: Because of this, this chart symbolizes how an individual is affected by the new whole that they are a part of.
The Marks Chart uses the Davison Chart and a Natal Chart from one person in the relationship to create a new Davison chart that tells how the relationship affects the individual; where potential meets individual
In conclusion, Synastry desribes how two individuals interact; Composite tells how to individuals compromise; Davison tells how two individuals create purpose; Marks tells how either individual is affected by the purpose.
Again these are my thoughts, if you must, please share yours respectfully.