Sesquiquadrate

Definition

A sesquiquadrate is a minor aspect of 135° — three-eighths of the zodiac circle, or 3 × 45°. It belongs to the eighth-harmonic family, and pairs with the 45° semi-square. The Ptolemaic doctrine, the classical core set, does not recognise it; the astronomer Johannes Kepler introduced it in the 17th century.

In Tradition

Most Western astrologers read the sesquiquadrate as part of the square family — dynamic and action-oriented, bringing friction and pressure, though with somewhat less intensity than the square itself.

In Practice

Astrologers treat the sesquiquadrate as an eighth-harmonic cousin of the square. When it is tight, it can carry as much weight as a wider-orb square. The usual orb is 1.5–2°. Semi-squares and sesquiquadrates tend to bring about concrete events, since the inner pressure they describe often works at a less conscious level than that of the square.

Historical Origin

Johannes Kepler introduced the sesquiquadrate in the 17th century as part of his harmonic aspect framework. It was not recognised by Ptolemy or in classical Hellenistic astrology.

Further Reading

• Robert Hand, Horoscope Symbols
• Sue Tompkins, Aspects in Astrology