How to Calculate Aspect Orbs: How Close Is Close Enough?
3 min read
You ask a friend whether you have Moon square Saturn. They say no, despite using the same birth details. The difference lies in a threshold.
Why an aspect disappears on another website
One site lists fourteen aspects, another nine. Usually they use different limits for how far from exact an aspect may be.
The orb is a technical but often poorly explained part of aspects. Here are the conventions, planetary distinctions, and ways to prioritize.
What an orb is: an angular allowance
Planetary separations rarely equal exactly 0, 60, 90, 120, or 180 degrees. An orb is the permitted deviation from that exact angle.
Subtract the exact aspect angle from the actual separation and take the absolute value. A natal square with a six-degree allowance covers 84 to 96 degrees.
Some traditional systems assign orbs to planets. Half of each planet’s allowance, its moiety, is added to the other’s. Two eight-degree planetary orbs give four plus four, or eight degrees, rather than sixteen. astro.how instead assigns one allowance to each aspect type, regardless of planet.
Common conventions: natal, synastry, and transit
There is no universal standard. An orb is a filter: wider settings add lines and can dilute attention.
Natal charts concern lasting structures. astro.how uses 7 degrees for conjunctions and oppositions, 6 for trines and squares, and 4 for sextiles; solar returns use the same settings. Synastry uses 3 degrees, or 2 for sextiles. Transits use 2 degrees, or 1 for sextiles, defining a time window around exact contact.
Why some widen luminary orbs and tighten outer-planet orbs
Two reasons operate: traditional luminary status and speed.
Traditional planetary orbs give the bright Sun and Moon more reach, sometimes eight degrees or more. astro.how keeps the same defaults for every planet, but luminary aspects can still take priority. The Moon travels about thirteen degrees daily and the Sun about one, so very narrow filters quickly exclude fast-moving contacts.
Slow planets differ. Neptune moves about two degrees yearly; a ten-degree orb between slow planets can describe nearly a decade. For personal interpretation, prioritize outer-planet contacts within two to three degrees; otherwise read them as background. See Uranus, Neptune, and Pluto.
Conjunctions make the contrast clear: a luminary conjunction may receive over eight degrees traditionally, while an outer-planet conjunction needs much tighter personal context.
Want to see what your chart looks like?
Create your chartTight aspects speak louder: setting priorities
When a chart has many lines:
- Choose the three to five tightest contacts.
- Prioritize Sun or Moon involvement, which concerns daily identity and emotional responses.
- Look for repeatedly contacted planets: three or more appearances can mark a hub.
- Leave borderline soft aspects for last: wide trines and sextiles often remain background.
Squares and oppositions may deserve earlier attention even when wider. Trines and sextiles depend more on tightness to avoid a list of compliments.
Orb reference table
| Aspect | Exact angle | Natal / solar return | Synastry | Transit | Note |
|---|---|---|---|---|---|
| Conjunction | 0° | 7° | 3° | 2° | Same or neighboring houses |
| Sextile | 60° | 4° | 2° | 1° | More meaningful when tight |
| Square | 90° | 6° | 3° | 2° | Can remain noticeable at slower speeds |
| Trine | 120° | 6° | 3° | 2° | Ease can make it unnoticed |
| Opposition | 180° | 7° | 3° | 2° | Often involves relationships |
| Quincunx | 150° | Not shown | Not shown | Not shown | Minor aspect |
These are astro.how defaults, rather than uniquely correct values. Different websites commonly use different filters. House systems can also change a chart’s appearance.
For names and glyphs, see the aspect index and chart symbols. Worked calculations appear in synastry orbs and transit windows, with natal interpretation in the aspects lesson.
Orbs are conventions. Choose a consistent system, record it, and use the same scale when comparing readings.