Orb
every reader
What the tradition reads
An orb is the margin of error astrology allows around the exact angle of an aspect, the number of degrees a pair of planets may fall short of or overshoot a perfect conjunction, sextile, square, trine or opposition and still be read as making that aspect at all. If two planets stand ninety two degrees apart, for instance, they are still read as square, with an orb of two degrees, since ninety degrees is the exact angle of a square and two degrees is the shortfall from it. Orbs are not fixed by any single rule: most astrologers allow a wider orb for the conjunction and for any aspect involving the Sun or Moon than for an aspect between two smaller or slower bodies, wider orbs for the major aspects than for the minor ones, and a narrower orb again for a technique that moves quickly, such as a transit, which most astrologers who use the technique limit to about one degree, tighter than the aspects of the birth chart itself are usually allowed. An aspect is read as strongest when exact and steadily weaker as it approaches the outer edge of its orb, so the orb functions as a kind of fading boundary around each aspect rather than a hard cutoff.
The story
Orb descends from the Latin orbis, a circle or a ring, by way of Old French and Middle English, arriving in English with the general sense it still carries outside astrology, a spherical or circular body, as in an orb of light or an orb held in a monarch's hand. Astrology's technical sense narrows that general circle down to one very specific ring: the small circular margin drawn, in effect, around the exact degree of an aspect, inside which the aspect is still considered to be operating. The narrowing from a broad, general circle to this one precise technical allowance reflects a habit common across astrology's inherited vocabulary, in which an ordinary word for a shape or a distance, aspect, house, cusp, ray, is quietly repurposed to name one exact measurement inside the wider practice of reading a chart, so that the astrological sense sits recognisably on top of the everyday one rather than replacing it.
Written from
Corpus key glossary:orb.