← Encyclopedia of Astrology · lesson 134/235
Shadow period
A planet's shadow is the stretch of the zodiac between its two stations — the degree where it turns retrograde and the degree where it turns direct again. Because the planet travels that stretch forwards, then backwards, then forwards once more, every degree in it is crossed three times. The shadow period is the whole time the planet spends inside that stretch, and it is longer than the retrograde itself.
The station and retrograde entries describe the turning and the backward motion. This one covers the before and after.
How it is worked out
Take a Mercury retrograde that stations retrograde at 20° Leo and stations direct at 5° Leo.
- Pre-shadow. Mercury, still moving forwards, first reaches 5° Leo — the degree it will later station direct at. From that day until it stations retrograde at 20° Leo, it is in its pre-shadow.
- The retrograde. It turns at 20° Leo and moves back down to 5° Leo.
- Post-shadow. It stations direct at 5° Leo and moves forwards again. Until it passes 20° Leo — the degree of the retrograde station — it is in its post-shadow. Once it is past, the cycle is over.
The two ends of the shadow are the two station degrees, and both can be read from any ephemeris weeks or months ahead.
How long it lasts
| Planet | Each shadow, roughly | The whole span, roughly |
|---|---|---|
| Mercury | 2 weeks | 2 months |
| Venus | 4–5 weeks | 3½–4 months |
| Mars | 2 months | 6–7 months |
For Jupiter, Saturn and the outer planets, the shadow periods are so long that they run into each other: the planet is in one shadow or another most of the year, and the idea is seldom used for them.
How it is read
Shadow periods are a modern idea, a product of astrologers watching retrogrades closely in ephemerides rather than a classical technique. They are read as the run-up to a retrograde and its aftermath.
- Pre-shadow is often described as a preview. The themes the retrograde will revisit start to surface: the problem that will need rethinking, the person who will come back, the plan that will need revising. Many astrologers suggest noticing what arises in this window, because it tends to return.
- The retrograde is the review itself, the stretch for the "re-" words.
- Post-shadow is read as working back up to speed. The planet crosses the same degrees a third time, and matters that were reconsidered are taken forward again, often with more understanding than the first time. Some treat the post-shadow as the time a decision made during the retrograde is tested before it is relied upon.
Because a transit to a natal point inside the shadow happens three times — once in the pre-shadow, once retrograde, once in the post-shadow — the shadow is also a practical way to see that a retrograde's three passes form one story told in stages.
Readings of the shadow are softer and more varied than the retrograde itself, and many astrologers do not use them at all. They are best taken as a frame for paying attention, not as a rule about when to start or sign things.
In a reading here
For shorter readings, the Current Sky section lists any shadow period of Mercury, Venus or Mars that falls in the reading's window, with the dates of the pre-shadow, the two stations and the post-shadow; the Almanac shows them too. The outer planets are left out, since they are almost always in shadow.