The viewpoint changes
Earth and the other planets travel around the Sun at different speeds. Their changing positions can make a planet appear to retrace its path against the background stars.
For an outer planet such as Mars, this happens as Earth catches up and passes it. The apparent reversal belongs to our view from Earth; Mars continues along its orbit.
In a zodiac table, retrograde means decreasing longitude. Moving from 18° to 17° within a sign is a simple example. Crossing from 0° Aries to 29° Pisces also decreases longitude around the circle.
A retrograde cycle has two turning points
Station retrograde
The apparent longitude changes from increasing to decreasing. The turning point marks the start of retrograde motion.
Retrograde passage
The planet moves back across degrees it recently occupied. This is the interval labelled retrograde in a chart.
Station direct
The apparent longitude changes from decreasing to increasing. The planet then crosses those degrees again in forward motion.
What astrologers call the shadow
The shadow is the zodiac interval between the two station degrees. The pre-shadow begins when the planet first crosses the later direct-station degree.
The post-shadow ends when it passes the earlier retrograde-station degree again. These passages require their own calculations; a current retrograde label cannot supply their dates.
A station is an instant defined by the change in motion. A planet moving slowly near one is not necessarily stationary at the exact time you are checking.
Natal motion and a current transit answer different questions
Retrograde at birth
Read the motion recorded beside the planet in your natal chart. Astrologers may interpret it as revisiting, internalizing or expressing that planet's themes less directly.
For Mercury, that could frame a question about how you revise an idea before expressing it. The label alone cannot establish a communication difficulty or a personal history.
Find natal motion in your birth chartRetrograde now
The sky condition is shared. A personal transit requires a measured contact between the moving planet and a factor in your birth chart.
When a planet retraces degrees, it can repeat a contact. The number and timing of contacts depend on the actual positions and the period examined.
Check contacts to your birth chartFor natal houses, Astriel uses calculated Placidus cusps by default. A retrograde label does not reassign a natal planet to another house; its calculated longitude determines its house membership.
Degree example · invented positions
Why one contact can happen more than once
Suppose natal Mercury is at 14° Virgo. A transiting planet first crosses 14° Virgo moving direct, then stations retrograde at 18° Virgo.
It crosses 14° again moving backward, stations direct at 10° Virgo, and later crosses 14° a third time. Each crossing reaches the same conjunction degree.
In this illustration, the shadow spans 10° to 18° Virgo. The first and third contacts happen during direct motion, so a retrograde-only search would miss them.
These numbers explain the sequence. They are not an event timetable or a prediction of three matching experiences.
Use the planet, placement and contact together
Start with what was calculated: the planet, its sign and degree, and its direction at the stated time. For a natal reading, add its house and aspects.
Then connect the planet's theme to the question you are exploring. Venus concerns values and relating; Mars concerns action and assertion. A motion label cannot replace those distinctions.
Plans, conversations and decisions still need evidence from the situation itself. A retrograde placement cannot establish that something will fail or should be postponed.
Explore each planet's meaningSources and calculation details
The astronomy explanation refers to NASA's StarChild guide linked above. Stations and shadows use conventional astrological terminology. The worked example uses invented positions to explain the geometry.
apparent geocentric ecliptic of date · tropical. Ephemeris: astronomy-engine 2.1.19. Computed .
The current status uses longitude change sampled one hour before and after the stated time. Very close to a station, this estimate does not establish the exact turning instant. Exact station and shadow calendars are not published here. Astrological interpretations are symbolic conventions, not established causes of personal events.
Astriel editorial · Reviewed 2026-09-20. Calculation methods and limits