I'm Elena Foster. I've spent five years reading synastry charts — comparing two natal charts to see how they interact — with couples, people considering a relationship, and people trying to understand why a relationship is doing what it's doing.
I wrote this because I keep seeing the same thing: people come to me with a sun-sign compatibility list that says they should be perfect together, or they've been told that a specific asteroid placement means they're soulmates, and neither of those things matches what they're actually experiencing. The astrology they've been given is not wrong in the sense of being fake — it's wrong in the sense of being incomplete. Sun signs are one layer. Asteroids are one layer. Neither of them is the technique.
Synastry is the technique. This article is my attempt to show what it actually is and how to read it without turning it into a verdict.
Synastry is chart overlay: you take two natal charts and compare them planet by planet, aspect by aspect, to see how the energies interact.
That's it. That's the technique. Everything else — the asteroids, the nodes, the fancy markers — is commentary on the technique, not a replacement for it.
The core layer of any synastry reading is the personal planets: Sun, Moon, Venus, Mars. These are the planets that describe the basic ways two people interact.
Here's how I approach it:
- Sun contacts tell you something about how the two people's core identities interact. A Sun conjunct Moon contact is different from a Sun square Mars contact. One is about recognition and emotional resonance. The other is about friction and energy.
- Moon contacts tell you something about emotional resonance — whether the two people feel at home with each other's emotional language.
- Venus contacts tell you something about how affection flows between them — what kind of love language lands, what kind doesn't.
- Mars contacts tell you something about how energy, desire, and conflict interact — not just sexual, but the whole way two people push against each other.
The aspects between these planets are the main thing I look at first. Conjunctions and oppositions are the strongest. Trines and sextiles are where things flow. Squares are where things get interesting — and where people often feel the most alive in a relationship, for better or worse.
The point is not to count good aspects versus hard aspects. The point is to see the pattern: where is there flow, where is there tension, where is there a theme that keeps showing up.
The angles in a chart — the Ascendant/descendant axis, the MC/IC axis — are the points where the chart meets the world. In synastry, contacts to the angles tell you something about how the relationship lands in each person's life.
Here's what I look for:
- Contacts to the descendant — the descendant is the partnership point in the chart. Planets from one chart hitting the other person's descendant tell you something about how the relationship shows up in the partnership space.
- The 7th house — the house of partnership. Planets from one chart landing in the other person's 7th house have a similar theme to contacts to the descendant.
- The MC/IC axis — the career/home axis. Contacts here tell you something about how the relationship interacts with each person's public and private life.
Here's where I need to be careful, because this is exactly the place where astrology gets oversold.
Juno is an asteroid associated with commitment, marriage, and the quality of the partnership bond. In synastry, Juno contacts can tell you something about whether the relationship has a marriage-quality theme — whether there's a commitment pattern in play. Juno conjunct the Sun, Juno trine the Moon, Juno on the descendant — these are markers worth noticing.
Lilith is an asteroid associated with raw energy, intensity, and the places where things get uncompromising. In synastry, Lilith contacts can tell you something about chemistry and intensity — the places where the relationship gets raw, real, or challenging in a way that's not easily smoothed over.
Both of them are useful. Both of them are secondary. Neither of them is a formula.
Here's the thing I want to be honest about: any article that tells you Juno conjunct Sun has an "87% marital success correlation" is inventing a statistic. I've never seen a study that measures that, and I've been reading astrology for five years. What Juno conjunct Sun actually tells you is that there's a commitment theme in the relationship — a sense that partnership matters to both people, or that the question of commitment is active. That's useful information. It is not a percentage.
The same goes for any other single marker. No asteroid, no node, no aspect is a formula. The pattern is the formula.
The nodal axis — the North Node and South Node — is one of the most useful markers in synastry, because it describes the relationship theme in a way that's often very clear.
Here's what I see in practice:
- North Node contacts often show up in relationships that feel like they're asking something of the person — relationships that push growth, that activate a direction the person is meant to move toward.
- South Node contacts often show up in relationships that feel familiar — relationships that recycle something old, that feel comfortable in a way that may or may not be useful.
The nodal axis doesn't tell you whether the relationship is good or bad. It tells you something about the theme — what the relationship is asking, or what it's repeating.
This is the part that makes the difference between a real synastry reading and a list of markers.
When you read a synastry chart, don't go marker by marker and add up points. Look at the pattern.
- Where are the strong contacts?
- Where is there flow?
- Where is there tension?
- Is there a theme that keeps showing up across different planets?
- Are the angles involved?
- Is there a nodal axis pattern?
- What does the overall picture suggest about how these two people interact?
The pattern is the answer. The single marker is almost always misleading.
Here's an example from my practice: two people came to me because they'd been told they were a "Juno match" and that meant they were soulmates. Their Juno was conjunct — yes. But their Moon contacts were hard, their Venus-Mars interaction was tangled, and the overall pattern suggested a relationship that would have chemistry but also real friction around emotional safety. The Juno marker was real. It was also incomplete. The pattern told the fuller story.
What synastry can do:
- Show you where the chemistry lives between two people
- Show you where the tension lives
- Show you the relationship themes — what the connection tends to activate
- Give you a language for what you're already feeling
- Help you see the pattern instead of just living it
What synastry can't do:
- Predict whether a relationship will work
- Tell you whether someone is "the one"
- Replace the actual work of being in a relationship
- Guarantee anything
Synastry is a technique for seeing. It's not a technique for predicting. If someone tells you their astrology can tell you whether your relationship will last, they're overselling it.
If you want to read a synastry chart, here's a practical way to start:
- Get both charts clean. Right birth data. Right times if you have them. Know where the uncertainty is.
- Look at the personal planets first. Sun, Moon, Venus, Mars. How do they aspect each other?
- Check the angles. Descendant, 7th house, MC/IC. Are there contacts there?
- Look at Juno and Lilith as secondary markers. Useful color, not the formula.
- Read the pattern. What's the overall picture?
The goal isn't to get a yes-or-no answer. The goal is to understand the relationship more clearly — where the chemistry is, where the tension is, what the relationship is asking.
Synastry is a real technique. It's been used in astrology for centuries. It's more useful than sun-sign compatibility lists, and it's more honest than asteroid formulas that promise percentages they can't deliver.
But it's still astrology. It's still a map of the terrain, not a prediction of the journey. The chart can show you where the relationship tends to go. It can't tell you what you'll do with that information, or what you'll choose.
That's the part that matters most. The technique is useful. The meaning is yours.
About the author: Elena Foster is a professional astrologer and the Lead Relationship Astrologer at My Zodiac AI. She has spent five years reading synastry charts with couples and individuals and specializes in relationship astrology, Saturn-Venus dynamics, and the intersection of astrology with attachment patterns. She wrote this article to explain the real technique behind synastry — the chart overlay method that actual astrologers use — and to be honest about what it can and can't do.
Last updated: August 26, 2026
Reviewed for accuracy against current astrological references.
This article is for educational and reflective purposes. It is not a substitute for professional counseling, therapy, or relationship support. Astrology can be a useful mirror for understanding relationship patterns — it cannot predict outcomes, diagnose behavior, or replace the actual work of being in a relationship.
No. Sun sign matching compares two signs based only on the Sun — it's a starting point for curiosity, not a compatibility method. Synastry overlays two full natal charts planet by planet: how your Sun, Moon, Venus, and Mars aspect your partner's, which houses your planets fall in, and how the angles connect. It operates on the whole chart, not one sign.
Start with the personal planets — Sun, Moon, Venus, Mars — and how they aspect each other across the two charts. Then check the angles: the descendant, the 7th house, and the nodal axis. Juno and Lilith are useful secondary markers — Juno for the commitment question, Lilith for raw chemistry — but no single asteroid or point is a formula. Read the aspects as a pattern, not a checklist.
No. A synastry chart shows where the chemistry lives, where the tension lives, and where the relationship asks for awareness — it doesn't predict a yes or no. A chart can't account for how two people actually behave, grow, or choose each other day to day. A tense aspect is never a guarantee of breakup, and a soft aspect is never a guarantee of success.
The nodal axis points to where the relationship theme lives — the familiar terrain each person is drawn to and the growth edge it asks for. When one person's personal planets contact the other's nodes, the connection often feels fated or significant. It's a strong sign of a relationship with a clear theme, not a judgment about whether that relationship is healthy.
