Aspect Orb

Definition

An orb is the wiggle-room around a perfect aspect — the angular distance two planets can stray from an exact angle and still count as being "in aspect." In modern Western practice the major aspects usually get an orb of roughly 6-10 degrees; the minor aspects get a narrower 1-3 degrees, and the orb widens when the Sun or Moon is one of the two planets. The orb decides whether two planets count as aspecting each other at all, and gauges how strongly the contact registers.

In Tradition

Modern Western astrologers treat the orb as the live working radius of an aspect: the tighter the orb, the stronger the contact, and partile — within about 1 degree — is the most intense form. Traditional Hellenistic and medieval Arabic-Persian sources instead use sign-based aspects adjusted by each planet's own "rays" or moiety (half its orb of light) rather than one fixed orb per aspect type. The modern single-orb idea refines that older doctrine.

In Practice

You measure how many degrees apart two planets are, compare that to the angle of the aspect you're testing (60, 90, 120, 180 degrees, and so on), and count the contact as active if the gap falls inside the orb you've chosen. Common modern Western defaults run to roughly 8 degrees for conjunction and opposition, 7 for trine and square, and 5-6 for sextile, with the Sun and Moon given an extra 1-2 degrees and the minor aspects (quincunx, semi-sextile, the quintile family) held to 1-3 degrees. Horary and electional work — answering a question, picking a good moment — usually call for tighter orbs, because the timing has to be precise. Whether the aspect is applying (still moving toward exact) or separating (already past exact) shades the reading further: an applying aspect speaks to what is still to come, a separating one to what has already happened.

Historical Origin

A single fixed "orb of aspect" is a modern Western convention. Traditional Hellenistic, Arabic, and medieval Latin sources work instead from each planet's own "orbs of the rays," or moieties. Sahl ibn Bishr (9th century) sets out the per-planet orb of light systematically in his Introduction to Astrology, and William Lilly's Christian Astrology (1647) preserves the same moiety scheme. The modern aspect-by-orb approach took shape across nineteenth- and twentieth-century Western practice.

Further Reading