What is a retrograde shadow period?
The shadow is the stretch on either side of a retrograde when a planet crosses the degrees it is about to retrace, or has just retraced. The pre-shadow runs until the planet turns back; the post-shadow runs from the moment it turns forward until it is past the degree where it first stopped.
Right now Mercury is in its pre-shadow. On 4 Oct 2026 it reached 5°02′ Scorpio, the degree where it will station direct, and it turns retrograde on 24 Oct 2026 at 20°58′ Scorpio.
Longitude runs across, time runs down. The hatched band is the shadow zone: the degrees between the two stations. Every degree in it is crossed three times: forward in the pre-shadow, backward while retrograde, forward again in the post-shadow. The numbered marks count the passes over its middle degree. Positions are computed four times a day from the ephemeris, dates in UTC.
Four moments make a shadow
Two stations, two edges, one band of sky.
A retrograde is bounded by two stations, the days the planet seems to stand still: the station retrograde, where it turns back, and the station direct, where it turns forward again. Between them it retraces an arc of the zodiac. The shadow is built from that arc's two ends.
The pre-shadow begins the day the planet first reaches the degree of its coming station direct. The post-shadow ends the day it passes the degree of its station retrograde again. In Scorpio, 2026, that band runs from 5°02′ Scorpio to 20°58′ Scorpio.
| Moment | Date, UTC | Mercury at | What happens |
|---|---|---|---|
| Shadow begins | 4 Oct 2026 | 5°02′ Scorpio | First reaches the degree of the coming station direct |
| Station retrograde | 24 Oct 2026 | 20°58′ Scorpio | Turns back, 20 days later |
| Station direct | 13 Nov 2026 | 5°02′ Scorpio | Turns forward, 20 days later |
| Shadow ends | 30 Nov 2026 | 20°58′ Scorpio | Passes the station retrograde degree, 17 days later |
Why the shadow exists
Mercury never stops or turns around. It runs round the Sun on the inside track, faster than Earth, and the zodiac position we give it is only the direction of the line from Earth through Mercury.
As Mercury catches up with Earth, that line swings forward more and more slowly, stands still, swings back while Mercury passes between us and the Sun, stands still again and swings forward. The backward swing is the retrograde; the forward swings just before and after it cover the same arc of sky. That shared arc is the shadow.
Earth and the inner planets seen from above the Sun. Mercury’s place in the zodiac is the direction of the line from Earth through Mercury; the faint line from the Sun carries that direction to the ring. Watch the ring mark go forward, back and forward again over the same degrees.
Every planet has a shadow
From 8 weeks to more than a year.
Every planet that turns retrograde gets a shadow, and its length follows the planet's pace. Mercury's window lasts 56.1 days on average: 17 in the pre-shadow, 22.2 retrograde, 16.9 in the post-shadow. Saturn's lasts 329.9 days, Pluto's 394.8.
The arc the planet retraces shrinks the other way: about 13.4° for Mercury and 16.4° for Mars, only 2.4° for Pluto. The pre- and post-shadow are nearly the same length for every planet, because the planet covers the same arc at nearly the same pace going in and coming out.
Mean lengths over all 1,821 retrograde windows of the eight planets with a station retrograde between 1900 and 2100, computed from the ephemeris. The share is the part of those two centuries each planet spends somewhere between a shadow's start and its end.
Neptune never leaves the shadow
Its next shadow begins before the last one ends.
Mercury is inside a window about 48% of the time, and Jupiter 73%. The slow outer planets hardly get out at all: Uranus is inside 99% of the time, with a median of just 4.2 days between one window and the next.
Neptune and Pluto never get out. Their windows last longer than the time between their retrogrades, so the next pre-shadow starts while the last post-shadow is still running: by 15.7 days for Neptune and 30.9 for Pluto, as a median. That held for every one of their windows from 1900 to 2100.
Each bar is one window, from the start of its pre-shadow to the end of its post-shadow, computed from the ephemeris. Drag along the figure, or use the arrow keys on it, to move the cursor. Solid ochre marks days when a planet is still in one window's post-shadow and already in the next one's pre-shadow.
The next shadows
Every planet's current or next window.
| Planet | Shadow begins | Station R | Station D | Shadow ends |
|---|---|---|---|---|
| Mercury · now | 4 Oct 2026 | 24 Oct 2026 | 13 Nov 2026 | 30 Nov 2026 |
| Venus · now | 31 Aug 2026 | 3 Oct 2026 | 14 Nov 2026 | 15 Dec 2026 |
| Mars | 5 Nov 2026 | 10 Jan 2027 | 1 Apr 2027 | 8 Jun 2027 |
| Jupiter · now | 17 Sep 2026 | 13 Dec 2026 | 13 Apr 2027 | 11 Jul 2027 |
| Saturn · now | 20 Apr 2026 | 26 Jul 2026 | 10 Dec 2026 | 15 Mar 2027 |
| Uranus · now | 25 May 2026 | 10 Sep 2026 | 8 Feb 2027 | 26 May 2027 |
| Neptune · now | 16 Mar 2026 | 7 Jul 2026 | 12 Dec 2026 | 2 Apr 2027 |
| Pluto · now | 12 Jan 2026 | 6 May 2026 | 16 Oct 2026 | 7 Feb 2027 |
Dates are UTC days. Each planet's page lists every window to the minute, and the calendar exports them to your own.
What the shadow means
The motion is astronomy. The meaning is tradition.
Astrologers read the pre-shadow as the time when the themes of a retrograde first surface, and the post-shadow as the time they settle. The usual advice is to treat the pre-shadow as a preview and the post-shadow as a slow return to normal, rather than to expect the retrograde to switch on and off on its station days.
None of that is something an ephemeris can check. What it can check is the geometry: the dates, the degrees and the three passes. Everything measured on this page comes from astronomy-engine (VSOP87), the same ephemeris behind every date on this site, as described in the methodology.
The averages cover 1,821 retrograde windows from 1900 to 2100. A different definition of the shadow, such as one that adds a few degrees of orb, gives different lengths; this page uses the station degrees exactly.
Shadow period, answered
What is a retrograde shadow period?
The shadow is the time on either side of a retrograde when a planet moves through the same degrees of the zodiac that the retrograde covers. The pre-shadow begins when the planet first reaches the degree where it will later station direct and lasts until it stations retrograde. The post-shadow begins at the station direct and ends when the planet passes the degree where it stationed retrograde. Inside that band of degrees the planet passes every point three times.
How long is the Mercury retrograde shadow?
Across every Mercury retrograde from 1900 to 2100, the pre-shadow lasted 17 days on average and the post-shadow 16.9 days, around a retrograde of 22.2 days. A whole window, pre-shadow to post-shadow, runs 56.1 days on average and between 53.6 and 57.3 days at the extremes.
Is Mercury in its shadow right now?
Yes. As of 16 Oct 2026, Mercury is in its pre-shadow: it entered on 4 Oct 2026 and stations retrograde on 24 Oct 2026.
Do other planets have a shadow period?
Every planet that turns retrograde has one, and the slower the planet, the longer it lasts. On average the whole window runs 56.1 days for Mercury, 107.7 days for Venus, 189.6 days for Mars, 292.9 days for Jupiter, 329.9 days for Saturn, 364.8 days for Uranus, 383.1 days for Neptune, 394.8 days for Pluto. Neptune's and Pluto's windows are longer than the time between their retrogrades, so the next pre-shadow starts before the last post-shadow ends.
Is a planet ever outside a shadow?
Mercury spends about 48% of the time inside a window. Uranus spends 99%, with only a few days between windows. Neptune and Pluto are never outside one: in every one of the 199 gaps for Neptune and 199 for Pluto between 1900 and 2100, the next window began before the previous one ended.
Is the shadow period real astronomy?
The motion is. The planet really does cross the same degrees of the sky three times, and the dates on this page are computed from an ephemeris. Calling those weeks a shadow, and reading meaning into them, is an astrological convention: astronomy has no name for them.
Every date and degree on this page is computed from the ephemeris, in UTC.