The orb is the tolerance allowed around the perfect angle between two planets; each school sets it its own way.
The orb is the margin of tolerance around an exact aspect that lets it still count in the reading.
An aspect is a precise angle separating two planets: 0, 60, 90, 120, or 180 degrees for the major ones.
In reality, the planets almost never land exactly on this angle. The orb sets the accepted margin: with an orb of 7 degrees around the square, two planets 83 to 97 degrees apart are still considered square. When the gap narrows, the aspect is called tight, and the more it would weigh in the reading.
The site uses orbs of 8 degrees for the conjunction and the opposition, 7 for the square and the trine, 5 for the sextile. When the Sun or the Moon are involved, they are widened by one to two degrees, giving 10, 8, and 6 degrees depending on the aspect, because the luminaries radiate more in the tradition.
This setting is a convention: a wider orb makes more aspects appear in a chart, a narrow orb keeps few and judges them sharper. You can also read whether the aspect is tightening or moving away from exactness, which the site indicates when the calculation allows. This effect is called application and separation: an aspect that is tightening is called applying, one that is moving away separating, two nuances that classical astrologers already distinguished.
Ptolemy, in the Tetrabiblos, speaks only of the five major aspects and gives no general margin figure.
William Lilly, in 1647, attaches an orb to each planet, wider for the Sun and the Moon, and adds the halves of the orbs of two bodies to know whether their aspect exists. André Barbault, in the 20th century, advocates instead tight orbs.
Classical astrologers use wide orbs that vary by planet.
Modern ones often use fixed and narrower ones, the same for all planets. Some judge that an orb too wide drowns the aspects, others that an orb too narrow loses them. Nothing makes it possible to measure which is more correct, for lack of a standard.
Schools do not all agree: the site sets out the positions without deciding for you, and states the setting it uses by default.
The authors and texts that establish or discuss this concept, with the passage when it is known.
Knows only the five major aspects.
Orbs attached to the planets, wider for the Sun and the Moon, whose halves are added together.
Advocates tight orbs.
The diagram’s figures are calculated by the site’s engine (Astronomy Engine) or taken from the recorded facts, never copied by hand.
| Aspect | Angle | Orb | With the Sun or the Moon |
|---|---|---|---|
| ☌ Conjunction | 0° | 8° | 10° |
| ⚹ Sextile | 60° | 5° | 6° |
| □ Square | 90° | 7° | 8° |
| △ Trine | 120° | 7° | 8° |
| ☍ Opposition | 180° | 8° | 10° |
It is the tolerance, in degrees, around the exact angle. If the square is at 90 degrees and the orb is 7, two planets 85 degrees apart are still in square, with a gap of 5 degrees. The smaller the orb, the more exact the aspect.
Because no measurement fixes them. Lilly assigns an orb to each planet, Barbault tightens them, other schools standardize them. The same chart can therefore show eight aspects for one astrologer and twelve for another, with neither being wrong.
8 degrees for the conjunction and the opposition, 7 for the square and the trine, 5 for the sextile. For the Sun and the Moon, 10, 8, and 6 degrees. These values are those of the calculation engine, identical on all pages of the site.