Half past ten at night, the sink full, and someone says the line: “I am not washing this again on my own”. Within thirty seconds the conversation has already left the kitchen. It has gone through the weekend at the in-laws', the trip that never happened, yesterday's tone of voice. Just after eleven, each of you is in a different room, and the dishes are still there.

Every couple that lasts has a fight like this one. The object changes (the dishes, the schedule, the month's money, someone's mother), and the fight is always the same: the same starting point, the same lines, the same ending. Whoever is inside it recognises the script by the second line and still cannot get out of it.

This is the most useful thing comparing two charts offers a couple who are already together. Asking whether you're a good match is for people who have just met. The question for the two of you sharing a sink is different: why do we always fight about this, and what is each of us actually asking for when we say that line?

What follows is what I look at when two charts are placed side by side. The technique has a name, synastry, and there is a separate post about it that explains the method. Here the subject is the real couple, dishes in the sink and all.

I will start with the limit, because in this matter it protects the other person, and she is not here to defend herself.

Reading your partner's chart does not give you permission to label him. “That's his Saturn”, said in the middle of a fight, shuts the conversation down instead of opening it, and turns a description into an accusation dressed in technical language. Ideally he knows about the reading, and better still, he reads it with you. A chart drawn up in secret and used as ammunition turns into a dossier.

The compatibility of two charts does not decide whether you stay together or not, either. That decision belongs to two adults, with the history they share, and no combination of planets weighs as much as that. Couples with synastry full of tension spend decades happily together, and couples with trines all over the place split up in two years.

And there is one point that allows no nuance. No chart justifies staying in a relationship where you are afraid: aggression, threats, control over your money, your phone, or who you talk to. This has a name and a way out, and the way out runs through real people. In Brazil, Ligue 180 answers free, any time of day. No Moon, no Pluto and no “karmic lesson” explains or excuses this.

Back to the sink. She wants to sort it out now, talking, before bed. He needs to leave the room, walk round the block and come back an hour later. To her, his leaving feels like abandonment. To him, her insisting feels like being cornered. Both are trying to calm down, each in the only way they know.

The piece that describes this in the chart is the Moon, the piece tied to comfort and security. A person's Moon says what they do when hurt and what they need to receive to feel normal again. When comparing two charts, one person's Moon is set alongside the other's Moon, Sun, Ascendant, Venus, Mars and Saturn, and that is where you see whether one person's way of calming down is something the other can actually offer.

A Moon in a water sign tends to need presence and to be heard all the way through. A Moon in air needs to talk it through, and with logic. In fire, it needs to act and move on fast; in earth, it needs a concrete gesture, and a washed plate counts as an apology. Put two different Moons together and you understand why one person apologises by washing the dishes and the other does not even notice an apology happened.

The trickiest contact is one person's Moon with the other's Saturn. It describes a relationship where one person feels criticised at the exact moment they needed comfort, and the other feels they provide structure and no one is grateful. Many long relationships carry this contact. Knowing it is there is what changes everything.

Some couples agree on the substance and fight over the delivery. She says “you never wash anything” and means “I'm exhausted”. He hears the word “never”, goes off to fetch the list of the three times he did wash up, and wins the argument while losing the night.

Mercury is the piece that describes how each person speaks, listens and processes a difficult conversation. Some need to say everything on the spot, and some can only answer the next day, after thinking it over. Some use exaggeration as seasoning («never», «always», «every time»), and some read every word literally. Neither way is wrong. The trouble starts when one hears the other through their own dictionary.

In synastry, one person's Mercury is compared to the other's Mercury, Moon and Saturn, and whichever planet of each falls in the partner's house 3 joins in too. Mercury with the other's Saturn, for example, tends to describe someone who feels corrected every time they open their mouth. With the other's Moon, it describes a conversation that gets the feeling right and the fact wrong, or the other way round.

This is the part of the reading that pays off fastest. A couple who discover that one speaks in feelings and the other in inventory can, for the first time, translate before answering.

The fight about the dishes sometimes ends in bed, and sometimes starts there. Mismatched desire is the conversation almost every couple puts off, and it is also the one that weighs most on the others.

Venus describes what each person finds attractive and how they like to receive affection. Mars describes how each person goes after what they want, and at what speed. In the comparison, one person's Venus is read against the other's Venus, Mars, Moon and Sun, and one person's Mars against the other's Mars and Venus. House 8 received, Pluto and Lilith come in when the subject is intimacy and surrender.

A fast Mars with a Venus that needs time and atmosphere describes a couple where one feels rushed and the other feels pressured. A strong Venus-Mars contact describes easy attraction, and easy attraction can live perfectly well alongside a Moon that never settles down. That is why the reading crosses everything: the chemistry says one thing, the security says another, and the couple lives both.

None of this turns into a score. It turns into a sharper question to ask each other, and it is usually far less awkward than the vague one.

Now we get to the dishes themselves. A couple's routine — who pays what, who remembers the appointment, who notices the soap ran out — lives in house 6 and in Saturn, and that is where you read how responsibilities are split.

The technique that explains this part best is house overlay: which house house each of the other's planets falls into. If his Saturn falls in your house 6, he tends to show up for you as the one demanding order. If your Sun falls in his house 6, you tend to become, for him, the one who fixes things. And it is almost never symmetrical: she feels she carries the household, he feels no one notices what he does, and both are describing the chart with precision.

The material of each chart comes in too: the element and modality that each has too much of, and too little of. When one has a lot of earth and the other almost none, the practical task falls alone into the lap of whoever has the earth, and turns into resentment within two years. Knowing this early lets a couple divide things on purpose, instead of by gravity.

This part depends on both people's birth time. Without it there are no houses, and the whole overlay disappears.

A single chart describes a person. The comparison describes the meeting, and the meeting has a property that only shows up when you read it both ways: sometimes the same contact exists from A to B and from B to A. Her Moon touches his Saturn, and his Moon touches her Saturn. When that happens, the fight has two doors, and either one of them can start it.

It is the pattern most recognised in a reading. What I see most is a couple arriving convinced that one of them is the problem, and leaving with the discovery that both make the same move, in swapped roles, depending on the day. Neither one carries the whole blame. Both hold the key.

The post about the patterns that keep repeating explains how to recognise a script that survives a change of scenery. In a couple, the scenery changes every week — the dishes, the trip, the end-of-year party — and the script stays.

Try this with your last three fights. Write down the sentence that opened each one and the sentence that closed it. If all three end the same way, the dishes were never the subject.

The couple reading it does not say whether you will last. It does not predict a break-up, does not mark a date for a crisis, and does not call anyone a soulmate. Whoever promises that from two charts is selling something else.

It does not give a score or a percentage. Any two charts already have dozens of contacts between them, and adding them up measures nothing, as the post on compatibility between signs shows with numbers.

It does not replace couples therapy or a difficult conversation. What it does is give words to that conversation, words that accuse no one. It also does not diagnose your partner: no planet makes someone a narcissist, cold or controlling, and using the chart for that repeats, in different clothes, the label the second section of this text forbids.

And it does not work the same way without birth times. Without them, Moon, Mercury, Venus and Mars are still read by sign and by aspect, and the routine, home life and intimacy — which live in houses 6, 4 and 8 — are left out.

On a calm evening, with no fight in the air, each person answers the same question in writing: when I'm upset, what calms me down, and what makes it worse? Three lines, without reading the other's answer before finishing.

Then swap the pages. In most couples, one person's answer describes exactly what the other does at the wrong moment. She writes «stay with me»; he writes «leave me alone for an hour». There it is: you have just read each other's Moon, without any chart at all.

The chart comes in afterwards, to show where each answer comes from, where the two fit together and where they will keep clashing. The sink will keep filling up. The difference is that the next sentence about the dishes can finally be about the dishes.

And the questions that come up most on this subject, with the short answer: