Aspect by Degree

Definition

Aspect by degree is a way of reckoning aspects in which the angular distance between planets along the ecliptic — measured in degrees — decides whether an aspect exists. Each aspect needs the distance to fall within a set orb of its exact value: conjunction 0°, sextile 60°, square 90°, trine 120°, opposition 180°. This degree-based method is the standard in modern Western practice. It produces "dissociate" or "out-of-sign" aspects whenever the degree-distance puts two planets in a classical aspect but their signs do not stand in the matching relationship.

In Tradition

Modern Western astrologers treat an aspect as active when the angle between two planets falls within a set orb — a leeway window — of an exact value. Orbs vary by school, but commonly run from about 5° for a sextile to about 10° for a conjunction or opposition, tightening for minor aspects. The reward is precision: you can test exactness and time when an aspect perfects. The cost is dissociate aspects that break the old Hellenistic sign-relationship rule.

In Practice

Astrologers find the absolute difference in longitude between each pair of planets, modulo 360°, and check whether it falls inside an orb-window around an exact aspect value. Typical orb tables run conjunction 8–10°, opposition 8–10°, trine 7–8°, square 6–7°, sextile 5–6°, and minor aspects 1–2°. Tighter orbs are often used for outer-planet pairs and for contacts to the Sun, Moon, and chart points. The exact-degree figure also times when an aspect perfects as planets move, and tells whether an aspect is applying or separating. Many modern astrologers work a hybrid: they judge primarily by degree-orb, but flag dissociate aspects — where the sign-pair is not in the classical relationship — as behaving differently from clean same-sign aspects.

Historical Origin

The earliest explicit orb table in the Hellenistic literature is in Porphyry's Introduction to Ptolemy's Tetrabiblos, chapter 55 (Holden notes it may go back to Zahel/Sahl): Sun 15°, Moon 12°, Saturn and Jupiter 9°, Mars 8°, Venus and Mercury 7°. Holden treats orb-based reckoning as a later layer added on top of the original whole-sign framework. The systematic degree-based method became standard in modern Western practice only across the late 19th and 20th centuries — through Ebertin's Cosmobiology, Hand's Planets in Transit, Marks, and Tompkins.

Definition

In Tradition

In Practice

Historical Origin

Further Reading