Bi-Quintile

Definition

A bi-quintile is an aspect of 144° — two quintiles, or 72° × 2. It belongs to the fifth-harmonic family, the aspects you get by inscribing a regular pentagon in the zodiac circle, and is geometrically an opposition minus a semi-quintile (180° − 36° = 144°). Together with the quintile (72°), semi-quintile (36°), and decile (18°), it forms a distinct minor-aspect set apart from the Ptolemaic five — conjunction, sextile, square, trine, opposition.

In Tradition

Modern Western astrologers treat the bi-quintile as part of the fifth-harmonic series, tied to creative individuality, distinctive style, and a kind of expressive inflection — not the friction of the fourth-harmonic aspects, nor the ease of the trine. The whole quintile family is widely seen as a Keplerian addition to the classical aspect set.

In Practice

Astrologers note a bi-quintile only when it falls within a tight orb — typically 1°–2° — since it is subtle and easily drowned out by closer Ptolemaic aspects. They read it as a secondary inflection on the chart rather than a main line of pressure: where it appears, it marks a note of personal creative shaping or distinctive technique. It is usually read alongside the quintile that tends to accompany it, since pentagonal geometry seeds several fifth-harmonic links across a chart at once. It is rarely used in horary or traditional electional work, where only the Ptolemaic aspects carry weight.

Historical Origin

The fifth-harmonic family — quintile and bi-quintile — entered the Western canon through the astronomer Johannes Kepler, in *Harmonices Mundi* (1619) and *Tertius Interveniens* (1610), as part of his case for valid aspect angles beyond the Ptolemaic five. The series was developed for modern practice by John Addey in *Harmonics in Astrology* (1976) and by humanistic writers including Dane Rudhyar.

Further Reading

• Johannes Kepler, Harmonices Mundi
• John Addey, Harmonics in Astrology
• Dane Rudhyar, The Astrology of Personality