AstroWay
Aspect orbs: how much margin still counts as an aspect
An orb is the difference between the actual angle separating two planets and the exact angle of an aspect. If the Sun and Mars are 64° apart, they are 4° away from an exact sextile (60°), and the orb of that sextile is 4°. The same word is used for the allowance: the largest deviation at which an aspect still counts. Astrology has no single rule for how large that allowance should be, which is why orbs are better understood than memorised.
Why aspects need a margin
Planets move continuously, and an exact angle between two of them lasts minutes or hours. If only an exact 90° or 120° counted, a birth chart would almost never contain an aspect. So an aspect is treated as a zone: its effect builds as the planets approach the exact angle and fades as they move away from it.
The main practical rule follows from this: the smaller the actual orb, the more strongly the aspect shows. A square within 1° is far more visible in the character than a square within 7°. The limit of the allowance only answers the question of when an aspect stops being taken into account. It does not make every aspect inside it equal.
Orbs by aspect
The most common modern approach gives each type of aspect its own allowance. The logic is simple: the stronger the aspect, the wider the orb. The conjunction and opposition get the most, the trine and square a little less, the sextile less again, and minor aspects very little.
Most astrology software works this way. The convenience is obvious: one table for the whole chart. So is the drawback: under this scheme Neptune aspecting Pluto gets the same allowance as the Sun aspecting the Moon, although the two carry very different weight.
Orbs by planet and moieties
An older tradition set the allowance by planet rather than by aspect. Each planet had its own "light", a zone within which it acts. Half of that light was called its moiety (from the Old French for half). Two planets were in aspect if the deviation from the exact angle did not exceed the sum of their moieties.
A hypothetical example: if the Sun is given a light of 15° and Mars 7°, their moieties are 7.5° and 3.5°, and any aspect between them has an allowance of 11°. For Mercury and Mars it would be noticeably smaller. Medieval and Renaissance authors describe this approach, William Lilly in the 17th century among them. Its strength is that the allowance depends on who takes part in the aspect. The figures for individual planets vary slightly between authors, so it is better to take them from a specific source than from summaries.
Tight orbs
Some modern astrologers deliberately narrow their orbs. The argument runs like this: a wide orb gives every planet five or six aspects, and the chart turns into a web where everything is connected to everything. A tight orb keeps only what genuinely stands out. Schools that work with midpoints often limit the allowance to one or two degrees.
The opposite extreme exists too. In Hellenistic astrology aspects were defined first of all by sign: any planet in Aries was in trine to any planet in Sagittarius. Degrees refined the picture but did not decide whether an aspect existed.
Why the Sun and Moon get more
In almost every approach the Sun and Moon get wider orbs than the other planets. The traditional explanation goes back to the same idea of light: the luminaries are the brightest bodies in the sky, so their zone of influence is larger. The practical explanation is different: the Sun and Moon describe the core of the personality, and astrologers notice their aspects even when the angle is far from exact.
The same extension is often given to the ruler of the Ascendant, and sometimes to the Ascendant and MC themselves. The slow outer planets (Uranus, Neptune, Pluto) are, by contrast, often given tighter orbs in aspects to one another, since such aspects last for years and are shared by a whole generation.
Typical values in modern practice
The table shows typical ranges found in modern textbooks and software. It is not a standard and not the view of any particular author, only a reference point.
| Aspect | Between personal planets | With the Sun or Moon |
|---|---|---|
| Conjunction, 0° | 7-8° | 8-10° |
| Opposition, 180° | 7-8° | 8-10° |
| Trine, 120° | 6-7° | 7-9° |
| Square, 90° | 6-7° | 7-9° |
| Sextile, 60° | 4-5° | 5-6° |
| Minor aspects | 1-2° | 2-3° |
Among the minor aspects the quincunx usually gets a little more, up to 3°, because it is used more often than the others.
Orbs in synastry and transits
In synastry, where two charts are compared, orbs are usually narrower than in a natal chart: two charts together produce a great many cross-aspects, and a wide orb makes the comparison meaningless. Priority goes to aspects involving the luminaries, the Ascendant and the personal planets.
In transits the orb is measured in time as much as in space. A transit of a slow planet is treated as active while it is within roughly 1-2° of the exact angle. For fast planets the allowance is smaller still, since they cross the angle in a day or two.
Applying and separating
An orb does not stand still. If the faster planet is approaching the exact angle, the orb shrinks and the aspect is applying. If the exact angle has been passed, the orb grows and the aspect is separating. At the same orb, an applying aspect is traditionally considered stronger.
Some astrologers build this into the allowance itself, giving an applying aspect a slightly wider orb than a separating one. The direction depends on the speeds of the planets and on retrograde motion, so it is better taken from the calculation.
How AstroWay shows the orb
In the AstroWay aspect table the orb is the actual deviation from the exact angle, not the allowance. The calculator sets the allowance by the pair of planets, and only aspects that fit inside it appear in the table. Next to the orb is a note saying whether the aspect is applying or separating. The table is sorted from the tightest aspect to the widest.
Keep in mind that another program with different allowances will show a slightly different set of aspects. The difference almost always concerns aspects near the edge of the allowance, which are the weakest ones.
Example: the orbs in Donald Trump's chart
In Donald Trump's chart the orbs of the major aspects range from 0°26′ to 4°12′.
The tightest is Jupiter (17°27′ Libra) trine Uranus (17°53′ Gemini) at 0°26′, separating. The near-exact angle makes this trine one of the most visible features of the chart, even though neither planet is a personal one.
At the other end is Neptune sextile Pluto at 4°12′. It is weaker both by orb and by composition: two of the slowest planets, an aspect shared by a generation. The Sun sextile Mars at 3°50′ sits close to it in the table but reads as weightier, because it involves the Sun and it is applying.
One more useful detail: the Sun (22°55′ Gemini) and Uranus (17°53′ Gemini) are about 5°02′ apart, and the Moon in Sagittarius is 5°34′ from an exact trine to Mars in Leo. An astrologer who allows the luminaries 8-10° would list both aspects. The AstroWay table does not. This is how the choice of allowance changes the list of aspects: at the edges, not at the centre. Aspects within 2°, such as the Sun opposition Moon or Venus conjunct Saturn, will be picked up by any school.
How each type of aspect behaves in a chart is covered across the Aspects section, including the page on the square.
Author: Lilia and the AstroWay teamUpdated: