Introduction to Relationship Astrology 1:
Objective Compatibility Measurements

– written by Philip Graves Jan 29 2003
– reformatted for WordPress, June 9th, 2016


What is relationship astrology?

In relationship astrology, we consider the astrological factors influencing human relationships and all forms of human interaction. There are several distinct types of factors that are influential, and when these are combined they give a complex picture as to the probable characteristics of the relations between any two individuals.

In this first part of the article, comprising two distinct but related subsections, we are going to consider factors within the birth chart, in isolation from any linkages between the birth charts of two particular people.


1. Natal Astrological Compatibilities and Incompatibilities

This term refers to compatibilities and incompatibilities between the relationship needs and behaviour of the two individuals as indicated in their respective birth charts.

The birth chart of each individual yields a great quantity of information of significance to that individual’s needs and behaviour in relationships generally, independently of the impact of his or her astrological connections to any other particular person. Anything and everything in the birth chart may be significant, since the personality is a composite of all factors therein, and relationship needs and behaviour ultimately stem from the overall personality, rather than small fragments of it. However, there are certain factors that are especially important specifically to relationship needs and behaviour, as follows:

(a) The Moon sign and house, and aspects to the Moon. The Moon is a keystone of the emotional nature, which of course impacts crucially upon personal relationships. It also highlights instinctual responses, the mother-image, and needs for being cared for and for security. In a man’s chart, it is often projected onto women more than consciously integrated into his personality, and therefore indicates by its sign placement and aspects characteristics of women to whom he is attracted.

(b) The Venus sign and house, and aspects to Venus. Venus strongly conditions the individual’s needs, behaviour, experiences and outward projections connected with feelings of love, as well as with beauty and aesthetic sensibilities. In a man’s chart, it can describe his ideal of female beauty, and complements the placement of the Moon to show characteristics of his ideal female partner.

(c) The Mars sign and house, and aspects to Mars. Mars affects the energies and impetus to action and activity of the individual – their level, timing, the form that they take (physical, mental, impulsive, reserved, etc.), and the areas of life in which they are manifested. It influences the manner in which the individual will make approaches to others, and the individual’s physical behaviour in a relationship. In a woman’s chart, considered together with the condition of that other great male archetype the Sun (her father-image), it can describe the kind of male energies, and therefore of man, to which she is attracted.

(d) The Neptune sign and house, and aspects to Neptune. The condition of Neptune influences the individual’s romantic sensibilities, areas of enhanced sensitivity, and potential for dreaming and self-delusion.

(e) The sign on the cusp of the 5th house, planets tenanting the 5th house, and aspects to these planets. These affect the attitude towards and behaviour in relation to giving love and experiencing fun.

(f) The sign on the cusp of the 7th house, planets tenanting the 7th house, and aspects to these planets. These affect the attitude towards partnership and needs from a potential or actual partner. They can describe characteristics of the type of partner to whom one is attracted and whom one attracts, regardless of whether or not these characteristics are at a conscious level one’s reasons for being attracted to him or her. Very often people are attracted to others whose Sun, Moon or Ascendant shares the sign on the cusp of their own 7th house.

(g) The sign on the cusp of the 8th house, planets tenanting the 8th house, and aspects to these planets. These affect the quality of the individual’s more passionate and sexual feelings, and the individual’s needs and behaviour in this area of experience.

Whenever considering the sign on the cusp of a house as an indicator, it is recommended also, by those who believe in the traditional rulership connections between signs and planets, to consider the placement of the house’s dispositor in the chart. A house’s dispositor is the ruling planet of the sign on its cusp. For instance, if Gemini is on the cusp of the 5th house, look to the sign and house placement of and aspects to Mercury in the birth chart, as an additional indication of the individual’s needs and habits in connection with love and fun – matters influenced by the fifth house.

Once you have obtained a picture from the assessment of all these factors of the relationship needs and behaviour patterns of each individual whose relationship you are considering, then compare the two people’s pictures, and look for areas where an indication in one is clearly compatible or incompatible, on a practical level of relating and understanding, with an indication in the other. You will thus be able to pinpoint likely sources of problems and, conversely, of harmony, that arise purely and simply from objective incompatibilities and compatibilities (respectively) between the two birth charts as indicators of relationship requirements and habits.


2. Objective Astrological Similarities and Disparities

This term refers to objective similarities and disparities between the key indicators of personality in the respective birth charts.

Even when the factors that affect the relationship needs and habits of each individual have been considered, it is worth taking a broader look at the overall differences and similarities between the personalities of the two individuals.

(a) Calculate the prevalence of shared signs among major chart factors. Make a list of the signs occupied by the Ascendant, Descendant, Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, North Node and South Node in each of the two birth charts. Then for each sign in the first person’s list that you come to, see if it occurs anywhere on the second person’s list; if so, cross them both off and count one matched pair. Keep doing this until only non-paired signs remain. If the number of pairs counted was considerably greater than the number of non-pairs, then on an objective level the two people have much in common. If there were as many non-pairs as pairs, or even more non-pairs than pairs, then the two people have little in common. The more signs in one chart that are not shared by a major factor in the other person’s chart, the greater the risk of areas where understanding will be altogether lacking. Consider specifically which signs are not shared, and how the lack of each of these signs as a significant component of one person’s personality will diminish mutual understanding. Where the opposite sign but not the same sign is present in the other person’s list, this is significant compensation since opposite signs are inverse expressions of the same principle and usually understand each other fairly well. Then try this whole exercise again without the Descendant, Jupiter, Saturn or the nodes, to see how much the two people have in common at the most basic levels of personality.

(b) Calculate the elemental and constitutional balances in each chart, and compare between the charts. Calculating the elemental balance means working out the relative prevalence of Fire, Air, Earth and Water. Calculating the constitutional balance means working out the relative prevalence of Cardinal, Fixed and Mutable. Conventionally there are rather crude methods for doing this, typically allocating an equal weighting to most planets’ signs and ignoring their houses altogether; but a more refined and thorough one of my own devising which takes into account the relative significance of each factor in the chart is as follows:

Factor: Sign weighting: House weighting:
Ascendant 32
Descendant 16
M.C. 16
I.C. 8
Sun 64 32
Moon 64 32
North Node 16 8
South Node 8 4
Mercury 4 2
Venus 8 4
Mars 4 2
Jupiter 16 8
Saturn 8 4
Uranus 4 2
Neptune 4 2
Pluto ½ ¼
Ceres 1 ½
Vesta, Pallas ½ (each) ¼ (each)
Hygiea, Interamnia ½ ¼
Europa, Eunomia ½ ¼
Psyche, Bamberga ½ (each) ¼ (each)
Juno, Amphitrite ½ (each) ¼ (each)
Chiron, Pholus 0 0


(i) Elemental balance: For each of the above factors, allocate the values indicated to the element corresponding to its sign and house places, using this guide:

Element: Signs: Houses:
Fire: Aries, Leo, Sagittarius 1st, 5th, 9th
Earth: Taurus, Virgo, Capricorn 2nd, 6th, 10th
Air: Gemini, Libra, Aquarius 3rd, 7th, 11th
Water: Cancer, Scorpio, Pisces 4th, 8th, 12th


(ii) Constitutional balance: For each of the same set of factors, allocate the values indicated to the constitution corresponding to its sign and house places, using this guide:

Constitution: Signs: Houses:
Cardinal: Aries, Cancer, Libra, Capricorn 1st, 4th, 7th, 10th
Fixed: Taurus, Leo, Scorpio, Aquarius 2nd, 5th, 8th, 11th
Mutable: Gemini, Virgo, Sagittarius, Pisces 3rd, 6th, 9th, 12th


Once you have finished, you will have values showing the strength or prevalence of each element, and each constitution, in each person’s chart. Assess how similar or different the elemental and constitutional balances are between the two charts. If in one chart one of the elements or constitutions is particularly deficient or accentuated compared with its status in the other chart, then there is a clear objective difference between the two people’s personalities in respect of this element or constitution. While often this will result in the two people having to make adjustments to accommodate each other’s personalities, such differences can also in some instances work well as a means whereby the strengths of one personality complement those of the other and counter-balance the weaknesses of the other. The two individuals can in this way feel more complete and effectual together than either does alone.


Continue to Part Two of Three: Synastry…

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