The planets do not live in isolation in the sky: they "look at" one another. The ancients described aspects in the very language of sight. Two planets in aspect see each other and can cooperate or clash; two planets without an aspect do not see each other and remain strangers. Aspects are therefore the way traditional astrology describes the relationships between the forces of the chart.
The five Ptolemaic aspects
Classical tradition, codified by Ptolemy in the Tetrabiblos, recognises five main relationships, known today as the Ptolemaic or major aspects.
| Aspect | Distance | Signs involved | Traditional nature |
|---|---|---|---|
| Conjunction | 0° | Same sign | Union, depends on the planets |
| Sextile | 60° | Two signs apart | Mild harmony, opportunity |
| Square | 90° | Three signs apart | Tension, friction, challenge |
| Trine | 120° | Four signs apart | Full harmony, ease |
| Opposition | 180° | Six signs apart | Polarity, confrontation, separation |
Strictly speaking, the conjunction was not always considered a true aspect, because the two planets do not "look at" each other but merge: that is why its nature depends entirely on the planets involved.
The logic of aspects between signs
In Hellenistic astrology aspects arose first of all from the relationship between signs, and only later from exact degrees. This logic explains why some aspects are harmonious and others tense.
- The trine joins signs of the same element: Aries and Leo are both fire. They share the same substance, which is why they understand each other.
- The sextile joins signs of compatible elements, fire with air or earth with water, and of the same gender, masculine or feminine. They support each other, but with less force.
- The square joins signs of the same mode but incompatible elements: Aries, cardinal fire, and Cancer, cardinal water. They share a rhythm but have opposite natures, and friction arises from this.
- The opposition joins complementary signs, of the same gender and mode, set face to face: they attract and oppose each other like two poles.
Signs in aversion
What about signs that lie one, five, seven or eleven places apart, at 30° or 150°? Tradition considered them in aversion: they do not see each other. A planet in the sign next to another, for example, has no relationship of sight with it. This idea is fundamental for understanding why, in tradition, the sixth, eighth and twelfth houses were considered difficult: together with the second, they are the houses that do not see the ascendant. Aspects of 30° and 150° were introduced as minor aspects mainly in the modern era, together with others proposed by Kepler.
Orbs
An aspect is rarely exact to the degree. Medieval and Renaissance tradition gave each planet an orb, a kind of radius of light within which its aspect is felt. The luminaries had the widest orbs, the smaller planets narrower ones. In practice, the closer two planets come to the exact aspect, the more intense their relationship.
Applying and separating
An essential distinction concerns movement.
- An aspect is applying when the faster planet is moving towards the exact aspect: the relationship is growing, the symbolic event has yet to come about.
- It is separating when the faster planet is moving away from it: the relationship is dissolving and belongs to the past.
This difference is decisive in horary and electional astrology, and in the birth chart too it helps you understand whether a dynamic is still developing.
How to read an aspect
To interpret an aspect it is not enough to know its type. Tradition suggests considering:
- the nature of the planets involved: a trine between Saturn and Mars is not like a trine between Venus and Jupiter;
- their dignity: a strong planet expresses even tense aspects better;
- reception: two planets in square that receive each other can cooperate despite the friction;
- the houses involved: aspects put different areas of life in communication.
Difficult aspects, not bad aspects
A chart with no squares or oppositions would be a chart without tension and, perhaps, without a drive to grow. The square forces a choice; the opposition forces a confrontation with the other. At Studio Esoterico Cornelio tense aspects are read as places of inner work, while harmonious ones are talents not to be taken for granted: a trine can also turn into laziness if it is not cultivated.
In short
- Aspects describe how the planets "look at" and relate to one another.
- The five Ptolemaic aspects are conjunction, sextile, square, trine and opposition.
- Their nature derives from the relationship between the elements and modes of the signs.
- Signs at 30° and 150° were in aversion, meaning they did not see each other.
- Orbs, application, dignity and reception complete the reading of every aspect.