Orbs, and How to Weigh an Aspect

An orb is the allowable deviation from an exact aspect. Two planets 118° apart are not exactly trine, but at 2° from exact they are unmistakably in trine. The orb is how much slack the aspect can carry and still function.

And the orb is not a technicality. It is the volume knob. An aspect at 0.2° is a defining fact of a life. The same aspect at 7° is background texture. A student who cannot weigh aspects will read every chart as equally loud everywhere — which produces the flat, everything-is-significant interpretation that makes astrology sound like a horoscope.

Learning to weigh is the difference between listing a chart and reading one.

The Hellenistic astrologers began with whole-sign aspects: two planets aspect each other if their signs aspect each other, regardless of degree. A planet at 2° Aries and one at 28° Leo are in trine because Aries and Leo are trine signs. Simple, robust, and the system this school's whole-sign house framework belongs to.

Degree-based orbs developed alongside and eventually dominated. The traditional method used moieties — each planet had its own orb, and two planets aspected when they came within the sum of their halves. The luminaries had the widest, the outer planets the narrowest.

Modern practice mostly uses fixed orbs by aspect type. Both approaches are defensible. What matters is consistency, and then judgement.

One genuinely important distinction the tradition made and most beginners miss: signs that do not aspect each other at all are in aversion — they cannot see one another. From any sign, the signs adjacent to it and those five signs away are in aversion: blind spots, not relationships. Modern astrology calls these the semi-sextile and the quincunx and treats them as minor aspects. The tradition treated them as the absence of aspect, which is a stronger and more useful claim.

Working orbs for the five Ptolemaic aspects:

• Conjunction, opposition, square, trine: up to about 8°
• Sextile: up to about 4°
• Aspects involving the Sun or Moon: allow 1–2° wider
• Aspects to the Ascendant or Midheaven: keep tight, 5° at most

Then weigh, using these rules in order:

1. Under 1° is the spine of the chart. Anything this tight is a structural fact of the person, not a feature of their psychology. Cite the number in a reading — "point two degrees" moves a person more than any adjective, because it is true.
2. 1° to 3° is loud. Clearly operating, clearly recognisable in the life.
3. 3° to 6° is present. Real, but one voice among several.
4. Beyond 6°, be sceptical. It is in the chart. It is rarely running anything.
5. Hard aspects outrank soft ones at equal orb. A 4° square is doing more visible work in a life than a 4° trine, because friction produces behaviour and ease does not.
6. Aspects to the luminaries and the angles outrank aspects between outer planets. Two outer planets in aspect describe a generation. An outer planet aspecting your Moon describes you.

Applying versus separating. If the faster planet is still moving toward exactness, the aspect is applying — building, strengthening, ahead of the person. If it has already passed, it is separating — waning, and often felt as something already worked through. Applying aspects are traditionally read as stronger.

Open your chart's data panel and sort the aspects by orb, tightest first. Your engine already does this.

Read only the top three or four. Those are running your life.

Then ask the question that turns a list into a reading: do these three describe the same problem? Very often the tightest aspects in a chart are not three separate facts but one fact seen from three angles. Finding that single underlying pattern is what a real reading does, and it is the whole method of the module that follows this one.

A chart whose tightest aspects, in order, are:

• Sun opposite Neptune — 0.2°
• Venus trine Pluto — 0.3°
• Saturn square Chiron — 0.9°
• Moon square the nodal axis — 1.4°

Four aspects under a degree and a half. A beginner would report them as four separate findings. Weighed properly, they are one thing said four ways.

The Sun–Neptune says the foundation would not hold shape. The Saturn–Chiron says the holding was withheld and could not be spoken. The Moon squaring the nodes says the need to be seen is the gate the whole life must pass through. And the Venus–Pluto says the capacity to love what is buried is already native — the resource, sitting right there among the wounds.

Three describe the same injury from different angles. The fourth is the tool for it. That is what weighing aspects gets you: not a longer list, but a shorter and truer one.

• Sue Tompkins, Aspects in Astrology — orbs, applying and separating, and how to prioritise.
• Chris Brennan, Hellenistic Astrology — whole-sign aspects and aversion, which most modern books omit entirely.
• Robert Hand, Horoscope Symbols — on aspect strength and the hierarchy of significance.