Ordinary synastry compares two birth charts. Both of them are frozen at a moment decades ago, which means the comparison between them never changes. Whatever your Venus does to his Mars, it has been doing it since you were born and it will still be doing it at eighty.
Great for describing a relationship. Useless for saying when.
Progressed synastry fixes that by comparing the charts as they are now. Each person's chart is advanced by secondary progression, a day for a year, and the comparison is run again. Because both charts are moving, and moving at different speeds, the contacts between them form, perfect and dissolve across a stretch of years.
That gives you a clock. And unusually for astrology, somebody sat down and counted whether the clock keeps time.
The Four Comparisons
The name is slightly misleading, because there is more than one comparison being made. Four charts are in play: two natal and two progressed.
| Comparison | What it describes |
|---|---|
| Her natal to his natal | The standing dynamic. Permanent, and the baseline everything else is read against |
| Her progressed to his natal | What she is currently bringing to who he actually is |
| His progressed to her natal | What he is currently bringing to who she actually is |
| Her progressed to his progressed | Where both of them are at the same time |
The two crossed comparisons in the middle do most of the work, and they get read in both directions rather than collapsed into one contact. A progressed contact means something different to the person whose chart is moving than it does to the person being arrived at. Steven and Jodie Forrest make the same point about ordinary synastry, that every contact gets entered twice, once from each person's point of view. Here it matters more, because the two directions are genuinely different events happening at different times.
Why The Contacts Have A Beginning And An End
This is the mechanical reason the technique works, and it is worth understanding before anything else.
In a natal comparison an aspect is either there or it is not, permanently. In a progressed comparison the progressed Sun moves roughly a degree a year and progressed Venus moves at a broadly similar rate, so a contact between two moving points approaches, becomes exact, and separates over a stretch of years rather than existing forever.
Westran quantifies this usefully, and the number is bigger than people expect. A two degree orb captures roughly four and a half years of that continuum. A three degree orb captures about six years.
So a progressed synastry contact is not a date. It is a window, and the width of the window is set by the orb you chose. Anybody handing you a day is handing you a rounding error.
Paul Westran's Research
Progressed synastry as a named method is largely the work of one person, and the reason to take it seriously is that he did the counting.
Westran, who runs positiveastrology.com, assembled a database of 1,300 public relationships and worked through them by hand between 2000 and 2004, completing the calculations in 2005. The dataset covered 1,790 marriages and 810 love affairs. Couples were included only where both birth dates and places were available and undisputed, where the relationship was verifiably intimate or romantic with a reliable start or marriage date, and where there was no arranged marriage or evident coercion.
The finding was that progressed aspects involving the Sun and Venus between the two charts turn up at the start of relationships far more often than chance would produce. Westran put the odds against the 2005 result arising by chance at roughly 900,000 to one.
Then he did the thing that matters more than the original result. Between 2004 and 2018 he collected a second set of 1,300 relationships and ran the study again, publishing the replication in 2019. A finding that survives being run twice on independent data is a different kind of finding from one that has not been.
His method pages are also unusually candid about their own construction, including why he used an orb of 2 degrees and 1 minute rather than a round 2 degrees. The study was calculated manually from an ephemeris, and the extra minute made the visual arithmetic faster and removed any ambiguity about how the ephemeris had rounded. That is exactly the sort of detail most research write ups quietly leave out.
How To Actually Use It
Read the natal comparison first. Same rule that governs all synastry work, and Arroyo and the Forrests both state it independently: the individual charts come first, then the natal comparison, and only then anything that moves. Progressed synastry can tell you when something is live. It does not tell you what it is. The natal charts do that.
Then look at the progressed Sun and progressed Venus, in both directions. Where is her progressed Venus relative to his natal chart, and his relative to hers. Those are the two placements the research singles out, so start there instead of scanning everything at once and finding whatever you went in hoping for.
Use a tight orb and treat the result as a window. Two degrees, giving roughly four and a half years around the exact contact. Wider orbs find you more contacts and each one means less.
Expect the window to close. A progressed contact separating is not a verdict on the relationship. The natal comparison is still sitting there and has not changed. What has changed is that a particular period of intensity around a particular theme has run its course.
What It Does Not Do
It does not predict who you will meet. The research is about the timing of relationships that already happened, between people whose charts were both already known.
It also does not override the natal picture. A spectacular progressed contact between two charts with almost nothing natal between them describes a window, not a foundation. See the best and worst synastry aspects for what the natal comparison is actually weighing.
And it inherits every limitation of progressions generally. The outer planets barely move, so progressed synastry is a Sun, Moon, Mercury, Venus and Mars technique in practice. If you want the slow planets to arrive somewhere within a lifetime, you want solar arc instead.
What To Actually Go Do
Take a relationship that already happened, one where you know roughly when it started. Yours, or a famous couple, since that is what the study used.
Progress both charts to the start date. Then find the progressed Sun and the progressed Venus in each chart, and check them against the other person's natal Sun and Venus, in both directions. Four points, two directions, that is the whole search.
If something is within two degrees, note it, and then note the dates two and a bit years either side. That is the window the contact was open, and it will probably be wider than the story you tell about that period.
Do this on a handful of past relationships before you do it on a current one. The technique is far easier to trust, and far easier to hold loosely, once you have watched it land and miss on things you already know the shape of.
Frequently Asked Questions
Do I Need A Birth Time For Progressed Synastry?
For the progressed Sun and progressed Venus, no. Westran's study deliberately used noon charts where no birth time was available, on the reasoning that missing birth times are common and usually harmless for these placements, while a missing or unreliable birth place is rare and a much worse problem. For anything involving progressed angles or houses, you need accurate times for both people.
Which Contacts Should I Look At First?
The progressed Sun and progressed Venus, read in both directions between the two charts. That is what the research isolated, and starting there keeps you from scanning dozens of contacts and finding whatever you were hoping for.
How Long Does A Progressed Synastry Contact Last?
Longer than people expect. At a two degree orb the contact is in play for roughly four and a half years, and at three degrees for about six. These are periods of a life, not dates in a diary.
Is Progressed Synastry The Same As Composite Or Davison?
No, and the difference is worth keeping clear. A composite builds one chart for the relationship out of midpoints. Progressed synastry keeps both charts separate and moves them. See synastry vs composite vs Davison.
What About The Moon?
The progressed Moon moves about a degree a month and crosses a sign in two and a half years, which makes it far faster than anything else in the progressed chart. Useful for shorter windows inside a longer one, but it is not what the Sun and Venus research is about.
Going Deeper
Westran's own material is the primary resource, and most of it is public.
- positiveastrology.com carries the full method, the definitions, the data, the control group results, and the replication study.
- When Stars Collide: Why We Love, Who We Love, When We Love Them (2006) is the book length treatment of the theory.
- He runs a progressed synastry group on Facebook where the technique gets discussed and worked through directly with him.
Recommended Reading
Book links below are Amazon affiliate links. As an Amazon Associate I earn from qualifying purchases, at no extra cost to you.
- Paul Westran, When Stars Collide: Why We Love, Who We Love, When We Love Them (2006).
- Paul Westran, method, definitions and replication data, positiveastrology.com.
- Stephen Arroyo, Relationships and Life Cycles, "Systematic Outline of Synastry," on reading the individual charts and the natal comparison before anything else.
- Steven and Jodie Forrest, Skymates, on entering every contact twice, once from each person's point of view.
Continue Learning
Next: what are progressions in astrology and how to read a synastry chart.