Good question about these different types of composite charts--I can give you a brief depiction of each and then maybe those who use different models can comment further.
The composite horoscope functions as a chart of the relationship. It may be derived by:
1. The Midpoint Method: Identifying the midpoints between two natal horoscopes and then plotting them in a third chart. Although the points do not represent any specific moment in time like the natal or even progressed charts, it symbolically reflects the nature of the relationship and an entity unto itself. House cusps can be found by establishing the exact midpoint between each cusp. (This is the method I use)
The midpoints are plotted by finding the midway mark between two given planets or points. If a person’s sun is 1 degree of Aries and another person’s sun is 1 degree of Leo, the composite Sun will fall in two opposing places. The nearer midpoint places the composite Sun at 1 degree Gemini, and the farther midpoint places the composite Sun directly opposite at 1 degree Sagittarius.
Because the horoscope is spherical and not linear, there will always be two midpoints exactly 180 degrees apart for every combination of planets. One will form a shorter arc and the other a longer one. The shorter arc is generally considered stronger, though both are important.
Often it is not easy to see the composite midpoint at a glance and the quickest way of deriving an accurate figure is to reduce the points to a degree between 0 and 360, add them together and divide by two.
To find the composite Eros for example, when the asteroids are at 15 degrees Aries 18 minutes and 27 degrees Scorpio 35 minutes, they can be reduced to 15.18 and 237.35 respectively, added together and divided by 2. This gives a far midpoint Eros of 126.26 or 6 degrees Leo 26 minutes and a nearer midpoint of the exact opposite or 6 degrees Aquarius 26 minutes. The following list reinterprets the signs into degrees of the circle.
The next method is a midpoint chart that uses location as a reference point: 2. The Derivative Method: The Ascendant and house cusps of the Derivative chart are ascertained by finding the exact midpoint between the two midheavens and then deriving the rest of the house cusps by the actual location of the relationship. This second technique is called the Derivative Method which is the same as looking up the MC, or midheaven, in a Table of Houses and copying the rest of the cusps for the birth latitude or in this case the latitude where the couple reside.
Another technique of composite chart construction calculates the midpoint in time and space between the two charts.
3. The Davison Method: This composite uses the halfway point in time, latitude and longitude. It does actually create a chart based on time and space. Those who use this method are more likely to note the planets in the signs and disregard the far midpoints.
I don’t work with Davison much though I know many astrologers do and find it valid and insightful. I am referring your to Astro.com’s ‘frequently asked questions’ to define the difference between ‘corrected’ and ‘uncorrected’.
What is the difference between the "corrected" and "uncorrected" Davison Relationship Chart?
The Medium Coeli (MC) computed for the time midpoint, which is the basis of the Davison chart, deviates very slightly (usually by less than 1 degree) from the composite MC (computed as the midpoint between the two personal MCs). The time correction applied to the standard Davison chart brings its MC into perfect alignment with the meridian axis of the composite chart. Most astrologers read the composite chart and the Davison chart together.
I thought I'd wake up this thread having discovered something relevant in a chart I've done. Robert Blaschke has written on different types of composite charts - I don't have the book title to hand but it's on his website Earthwalk Astrology. Really worth looking up. Very briefly, he sees the Davison as representing outside forces acting on the relationship.
Having just read the book in the last few days, I set a chart up - I'm never sure what the rules are (if there are any) about whether you should do a composite when there is no "relationship" as such - I think there's no harm in it, as long as you see it for what it is, and don't get carried away with it. Or, as with this one, let it put you off before you start if it's challenging!
Anyway - what I found in a Davison chart with someone I'm not in a relationship with, was the following, which made me sit up and take notice!! I'm not going to post the chart for now.
Chiron is in the 4th at 28.43 Pisces, with Eros at 29.24 Pisces, in a Grand Water Trine with an immense 9th house Jupiter at 28 Cancer (boy is it happy there, in sign and house) and an angular (1st house conjunct AC) Neptune at 23 Scorpio. So there was a great deal of swirling, watery, deeply emotional and healing energy, all attached to Eros, at the time and place where the chart is set. That Jupiter just expands what is already a very powerful Eros/Chiron conjunction and brings all that loving nurturing energy in there. It's almost too much. And all without an apparent way out (I've read, and having a Grand Water trine in my natal chart I agree, that without an outlet, the energy in Grand Trines can literally swirl around and never be expressed).
There's a challenging square from Chiron/Eros to an 8th house Gemini Moon - lots and lots of words want to come out, but they're scared to, partly because of the real fear of overwhelming someone who may not want it or may not be in a position to accept it.
And - the last time we came face to face with each other, when neither of us was expecting it, Eros was at 29.37 Pisces. So it was the Eros return for the Davison chart on that day of all days (and yes, I have set the Eros return chart, and it comes out conjunct a 3 Aries ascendant)
As of today, the progressed IC of the Davison is 29.09 Pisces, and the progressed Chiron unbelievably 29.24 Pisces, so conjunct the chart Eros to the minute. So the transits and progressions - at least in this particular case - to the Davison seem hugely significant, more so than with the more usual midpoint composite chart. There is a sense of something hovering with this - that's badly put but I don't know if I'm at the end of something, and am going to have to face letting go, or whether I'm at the beginning of something which can't yet express itself.
I've been wondering about 29 Pisces - it seems to represent not only the fullest possible energy of Pisces, but also the culmination of the entire zodiac. No coincidence then, that I've just come across these lines written by the poet Rainer Maria Rilke:
"For one human being to love another, that is the most difficult of all our tasks, the ultimate, the last test of proof, the work for which all other work is but preparation".
These lines seem to sum up 29 Pisces - the work for which all other work is but preparation. Pisces is unconditional love, and 29-30 degrees the ultimate expression of it. To find the Davison Eros there, conjunct Chiron, and now Chiron progressed to the exact minute of Eros on the progressed IC, seems quite extraordinary. Whether or not my love for this man is ever reciprocated, the chart shows an intense, nurturing, erotic healing energy present at the point in time and space where this chart is set. And it already is a healing journey for me, whatever the outcome.
The Sabian symbol for 3-4 Aries, the Ascendant of the Eros return chart, is "Two Lovers Walking Down a Secluded Path"...
Oh, and another thing .. there was also a partial solar eclipse on the exact degree of the Davison Descendant, conjunct Sun/Mercury, 3 days before the date of the chart.
Thank you for revitalizing this thread. I too find the Davison charts quite interesting--they are set for a 'real' place between the two people and that suggests they address yet another aspect of relationship. I am wondering right now about transits to the Davison. Whenever a significant shift in a relationship takes place, there is usually an outer planet transit to the composite or progressed composite. I know it's a ways off, but I wonder what Uranus over 29 Pisces will bring!
Here is an excerpt for Eros and Chiron in the composite and and Eros and Jupiter:
Composite Eros and Composite Jupiter Love is a believing creature. --Ovidio
Jupiter in the composite chart by house, sign and aspect can indicate the area, style and contingencies that give the relationship a sense of meaning and purpose. It can represent a mutual support, belief and growth. Composite Jupiter encourages the couple to travel, not just physically but mentally and spiritually as well. Conversely, if Jupiter is heavily challenged in its position in the composite chart, it can mean a lack of support or mutual belief that makes maintaining the relationship quite difficult.
When Eros mixes with Jupiter, the condition of both bodies will determine the nature of the combination. A strongly placed Jupiter with supportive alliances through sign and aspect can make the erotic experience of love and union a powerful basis for relating. If, however, Jupiter challenges outer planets, contradicts Saturn or is in an incongruent sign, the meeting with Eros can suggest conflicts and disruption.
Eros and Jupiter can mix to incline the couple towards indulgence in each other setting their own needs above those of business or other responsibilities. This can be a great asset in a relationship that might otherwise become entrenched in work or mundane concerns. In a relationship that is already predominately based on pleasure, it could tip the couple into a routine of over indulgence with addiction and obsession as a possible result. Jupiter expands whatever it touches and contacting Eros will expand erotic desires expressed in the union. These can be creative or destructive.
With the conjunctions, oppositions, trines and sextiles, the attraction to each other is heightened along with a sense of mutual purpose. The couple can feel that they were meant to be together and in doing so are fulfilling an aspect of their destiny. When they express Eros, by merging erotically or creatively, they evoke the expansive and optimistic nature of Jupiter. Being together then brings a sense of meaning.
When the aspect is the square or inconjunct, the same sense of meaning may be evoked although the couple can experience conflict in styles of expression or actual beliefs. Being together can highlight the differences more than the commonalties making the relationship seem like it hangs off the edge of harmony much of the time. If Jupiter is harshly aspected, there can be a difference of belief systems that seems impossible to bridge. This contrast will awaken with erotic exchange regardless of the nature of the Eros aspect.
An unencumbered Jupiter/Eros combination will want to soar to the vast reaches of the known universe. There will be a sense of freedom and rapaciousness to the relationship that serves to lift it well above the mundane and ordinary walks of life. However Jupiter fits in to the unique and particular aspects of a composite chart, it will seek to expand, mythologize and aggrandize the path the couple chooses to follow. If this is through the medium of erotic union, the full meaning of transformation may be glimpsed again and again.
Composite Eros and Composite Chiron
The only way of knowing a person is to love them without hope. --Walter Benjamin
If Chiron is seen only as a symbol of the wounded healer, it represents a place where we are deeply damaged. Chiron experienced the core meaning of rejection and the ongoing suffering that comes from a wound that may be acknowledged but not healed. This is a place of great pain and suffering and also a place of empathy, love and compassion. Where Chiron is found marks our greatest anguish and also our greatest ability to relate with deep emotional tenderness.
But Chiron is more than a lame centaur. He represents more than an old wound that refuses to heal. He is the spirit of adventure that prepared heroes for their impossible journeys! He instills in us the audacity to attempt and the impetus and cheek to dare to be different. He’s about ‘super powers’ in every sense of the word! Chiron the teacher inspires us to do the 'undoable', conferring courage, prowess and daring. Composite Chiron does no less!
Chiron in the composite chart can indicate an area of sensitivity for the couple as well as the key to breakthroughs and adventures. It can be where they feel vulnerable to rejection, judgments around the body or physical appearance, and handicapped, often in invisible ways. It can be were they train very hard to overcome obstacles others see as overwhelming or impossible. Composite Chiron may also suggest an area of empathy, sensitivity and commonality for those who have been brave enough to face their wounds. When Eros touches Chiron, either the wound or the compassion or the audacity may be awakened. Often it is a mixture of all three.
When composite Eros conjuncts or opposes Chiron, it can seem like the couple have come together to heal their deepest hurts or attempt their wildest dreams. It is important to realize that this is no guarantee that healing or actualization will occur. Eros longs for merging and intimacy and, when Chiron is pulled in, there can be tremendous resistance to go so deep into vulnerability. The relationship can be fraught with levels of resistance, defense and protection. If they persevere however, they can emerge from the underside of pain and preparation more whole, healed and frisky!
All the Chiron contacts, including trines, inconjuncts and squares, seem to evoke issues around the body. There can be a feeling of inadequacy, inferiority, and even disgust that puts an understandable strain on intimacy. Sometimes the feelings of one person towards the other person’s body emerge later in the relationship, after a period of time. Then one may be accused of getting too fat, too thin, too soft or hard. It can symbolizes a rejection of an extremely personal kind that may be very difficult to overcome. Conversely, this contact can indicate an acceptance, compassion or even compulsion for the lover’s body. They may find erotic awakenings in training the bodies for some task of competition—Chiron invented the gymnasium!
The square between composite Eros and composite Chiron may be the most difficult aspect for the union as it appears to occur the least frequently in those who are actually together. This may mean that a couple with this contact is inclined to avoid any further relationship, although this is not always the case. The entire chart must be examined as well as the individual natal charts and synastry to get a feeling for what predominates in the relationship.
The inconjuncts seem to occur more commonly in the composite contacts between Eros and Chiron, yet they also coincide with these same issues of physical appeal, attraction and rejection. Given the high percentage of composite charts that have Eros/Chiron aspects, there appears to be a fascination for a relationship that can evoke both vulnerability and impudence! It is likely that the line between attraction and repulsion could be friable where Chiron is concerned or that what was once seen as an attribute, slightly altered becomes a deterrent and visa versa. Chiron Eros can indicate a relationship that brings together two people of different generations.
Kim - thanks for this, I'm fascinated by the connection of Eros and Chiron.
I'll keep an eye out for the Uranus transit to the Davison. It's currently sextiling our composite Sun in Taurus, both the Davison one and the other composite one, which is on the same minute as my Mars (and is 2 degrees from his Venus). So I'm beginning to think that's what's woken this up!
The thing about composites of any kind--and I say this often so possibly repeating myself here--is that we have a composite chart with every person on the planet...and everyone who has every lived. Those billions of charts are getting insane numbers of awesome aspects every day but we don't know it because we don't know billions of people. We only have our handful of others and those are the composites that 'count'. So a composite is not really applicable unless there is a relationship--and often the beginning or change of that relationship is marked by transits to the angles (if the birth times are accurate). And they keep working even when the relationship is over!
My ex husband's comp with me had transiting Jupiter conjunct the 4th house cusp when my granddaughter was born--even though I had not had anything to do with ex for decades! The family was expanding and the relationship--as co-parents--was still reflected in the chart. Interesting!
But if we had never met, that transit would have been over that point as well, just not meaningful to either of us because the comp wasn't 'activated'.
Uranus is the great awakener! Let us know how this goes!
'Follow your bliss and doors will open where once there were only walls.' Joseph Campbell
Kim - thanks, yes I'm always conscious of reading too much into composites for "might be" relationships, bearing in mind I have a composite chart with someone I sit next to on a bus for 20 minutes! But I do sometimes let my curiosity get the better of me particularly if I'm pretty certain about the birth time, even if it's based on strong intuition rather than factual knowledge.