Aspects, the Lunar Nodes and Midpoints

A chart is not only a set of planets in signs and houses. It is also a set of relationships between them: angular distances that tradition reads as the planets seeing one another, points defined by the Moon’s orbit rather than by any body, and, in a much later school, the points exactly halfway between two planets. This article takes them in historical order.

The aspects

Two bodies are in aspect when the angular distance between them, measured along the zodiac, is close to one of a short list of figures: 0 degrees (conjunction), 60 (sextile), 90 (square), 120 (trine) and 180 (opposition).

Why these five

The list is not arbitrary. Each of those angles divides the circle by a whole number: 1, 6, 4, 3 and 2. And each connects signs that share, or pointedly do not share, an element and a modality.

• A trine joins signs of the same element: Aries, Leo and Sagittarius are all fire.
• A square joins signs of the same modality and a different element: Aries, Cancer, Libra and Capricorn are all cardinal, and no two neighbours in that cross share an element.
• An opposition joins a sign to its complement, the same modality across the circle.
• A sextile joins signs of compatible elements, fire with air or earth with water.

Strictly speaking, the conjunction is not an aspect in the oldest Greek sense, since the planets are together rather than looking at one another; but it has always been read alongside them. Hellenistic authors thought of aspects first as relations between whole signs: a planet in Aries “sees” a planet in Leo by trine, whatever the exact degrees. The degree-based reading with orbs was refined later, in medieval practice.

Tradition gave the aspects characters. The trine and sextile were read as harmonious, the square and opposition as tense. That is a statement about manner, not about whether something happens, a distinction horary astrology insists on.

Orbs

Exactness matters. The orb is how far from the exact figure an aspect is still counted, and a tight aspect speaks more loudly than a wide one. It is better to know the orb of every aspect and weigh it than to treat the word “aspect” as a yes or no. A trine within one degree and a trine at seven degrees are not the same statement.

Medieval astrologers attached the orb to the planet rather than to the aspect: each body carried a sphere of light of its own size, larger for the Sun and Moon, smaller for Mercury or Saturn, and two planets were in aspect when their spheres touched. Modern practice more often gives each aspect its own orb.

The minor aspects

Later centuries added more: the semisextile at 30 degrees, the semisquare at 45, Kepler’s quintile at 72, the sesquiquadrate at 135 and the quincunx at 150. Johannes Kepler, who introduced several of these in the early seventeenth century, was looking for harmonic ratios rather than for new meanings.

They are best used sparingly and with tight orbs, for a plain reason: the wider the orb, the more of them there are, and a chart in which every pair of bodies is in aspect to every other has stopped saying anything.

The lunar nodes

The Moon’s orbit is tilted about five degrees to the ecliptic, so it crosses that circle twice each month: going north at the ascending or North Node, going south at the descending or South Node. They are not objects. They are the two ends of a line, and the South Node is always exactly opposite the North. Every aspect the South Node makes is one the North Node has already made from the other side, so counting both double-counts a single fact.

Why tradition watched them

The nodes matter because eclipses happen at them. A new or full Moon close to a node is a solar or lunar eclipse, and that is the whole of why tradition watched them. In medieval Western astrology they were called the Dragon’s Head and the Dragon’s Tail; in India they are Rahu and Ketu, and they hold the status of grahas there. The nodes move backwards through the zodiac, completing one full turn in about 18.6 years.

Mean node and true node

There are two nodes to choose from, and the choice is real.

• The mean node is the smooth long-term motion of the line, a polynomial in time, and it is always retrograde. It is what classical tables give and what most traditional work assumes.
• The true node is taken from the Moon’s actual orbital plane at the instant asked for. It swings as much as 1.6 degrees either side of the mean node over roughly 173 days, and during part of that swing it moves forwards.

Either is defensible. What matters is to know which one a chart uses before reading a tight aspect to the node, since the difference can be well over a degree.

Midpoints

A midpoint is the degree exactly halfway between two bodies, measured the short way round. The midpoint of 350 and 10 degrees is 0, not 180. When a third point falls on that degree, the school that uses the technique reads it as the two planets acting through the third. It is written as A = B/C, so “MC = Mars/Saturn” means the Midheaven stands on the midpoint of Mars and Saturn.

A modern layer

This is a modern technique and should be labelled as one. It belongs to Reinhold Ebertin and the Kosmobiologie school of the twentieth century, built on the earlier work of Alfred Witte and the Hamburg School. It has no classical pedigree at all: Ptolemy would not have recognised the question. That is not an objection to using it. It is a reason to keep it distinct, so that a reading which claims a two-thousand-year lineage is not quietly mixed with one that is less than a century old.

The ninety-degree dial

The ninety-degree dial is what makes the technique practical. Fold the circle into quarters and every hard aspect, conjunction, square and opposition, lands in the same place, so a point that squares a midpoint counts as standing on it. The technique treats the hard axis as one structure, and half the contacts would be invisible on the raw longitudes. Ebertin’s school added the semisquare and sesquiquadrate as well, which is a further fold of the same dial into forty-five-degree units.

Midpoints in solar arc

Midpoints matter most in solar arc directions. The whole chart is directed forward about one degree a year, so a directed point crosses a natal midpoint over roughly a year of life. A midpoint picture formed by direction is therefore a period rather than an instant: an orb of half a degree says the picture is roughly half a year from its centre, which is the useful thing to know about a condition that lasts.

How to read them

Where the tradition genuinely names a pair (Mars/Saturn, Sun/Moon, Saturn/Pluto) the reading of that pair has a literature behind it. Every other combination is best composed from what each half contributes, rather than invented as a doctrine for a pairing nobody wrote one for.

Read them tightly. Orbs are one degree, at most one and a half, because a midpoint is a point and not a body; there is no light to spread. And read them as description rather than event. Mars/Saturn is not an accident: it is effort against resistance, which is a shape a great many different years of a life can take.