Shadow Period
Definition
The shadow period, in modern Western astrology, is the stretch of time before and after a retrograde when a planet is crossing the very degrees of the zodiac it will go back over — or has just gone back over — while retrograde. The pre-retrograde shadow runs from the moment the planet first enters that to-be-retraced stretch until it reaches the retrograde station. The post-retrograde shadow runs from the direct station until the planet leaves the stretch on its second forward pass, having now covered those degrees three times in all.
In Tradition
Modern Western astrologers read the shadow period as carrying retrograde-like undertones, with the planet seen as either getting ready for, or finishing up, the ground the full retrograde cycle covers three times over. Astrologers agree the shadow idea has no classical precedent — it is a 20th-century Western refinement, built from the sense that retrogrades cast a kind of fore-echo and after-echo. They disagree on how strongly the shadow stretches rival the retrograde itself.
In Practice
An astrologer marks the shadow-period boundaries from an ephemeris — a table of daily planetary positions — by noting the degree of the coming retrograde station and tracking back to when the planet first reaches that degree on its earlier forward pass; that is where the pre-retrograde shadow begins. The post-retrograde shadow ends when the planet, having turned direct, finally moves past the original retrograde-station degree. Commitments and decisions made while a planet is in the to-be-retraced stretch are flagged as likely to come up again during the retrograde itself. Mercury's shadow periods get the most attention in popular Western astrology, but the same reckoning applies to every planet.
Historical Origin
The shadow-period doctrine is a modern Western formulation with no classical precedent: classical sources discuss retrogrades and stations, but they do not single out the pre-retrograde and post-retrograde stretches as distinct interpretive periods. The concept is set out in 20th-century Western literature including Sullivan's Retrograde Planets and Hand's Planets in Transit, and it continues to be elaborated in the popular Western tradition around Mercury retrograde.
Etymology
Origin: English. Meaning: Metaphorical — the retrograde casts a "shadow" over degrees before and after.
Further Reading
- Erin Sullivan, Retrograde Planets
- Robert Hand, Planets in Transit