An ordinary birth chart draws a handful of aspects: conjunctions, oppositions, squares, trines and sextiles. These are the angles that divide the circle by one, two, three, four and six. But the circle can be divided by other numbers too. Two planets 72 degrees apart divide it by five. Two planets about 51 degrees apart divide it by seven. Those angles are real, and some astrologers find them very telling, but on an ordinary wheel they are almost invisible. Nobody looks at a chart and spots a 51-degree gap by eye, except perhaps the kind of person who also notices that a picture on the wall is two millimetres off level.

Harmonic charts are a way of making those hidden angles visible. The method is simple, and once you see it, the rest follows.

How a harmonic chart is made

Take every position in your birth chart as a number of degrees around the circle, from 0 at the start of Aries to 360. Multiply each one by a chosen whole number. Then take away 360 as many times as needed to bring it back onto the circle. The result is the harmonic chart for that number.

It sounds arbitrary, and it is not. Here is what multiplication does: an aspect of 360 divided by n degrees in the birth chart becomes a conjunction in the nth harmonic.

An example shows it best. Imagine a chart with the Sun at 10° Aries and Mars at 22° Gemini. They are 72 degrees apart, a quintile, the fifth part of the circle. Hardly anyone would notice it on the wheel. Now multiply both by five. The Sun at 10 degrees becomes 50 degrees, which is 20° Taurus. Mars at 82 degrees becomes 410 degrees, minus 360, which is also 50 degrees, also 20° Taurus. In the fifth harmonic chart the Sun and Mars are exactly conjunct. The quiet aspect has become the loudest thing on the wheel.

The same happens to the related angles. In the fifth harmonic, the biquintile of 144 degrees also becomes a conjunction. In the seventh, the whole family of septiles does. In the ninth, the noviles of 40 degrees and their multiples do, which includes the trine, since 120 is three times 40.

The three harmonics in our report

Each harmonic takes its meaning from the number that makes it, and our report offers the three that astrologers find most telling.

The fifth harmonic shows creativity and craft: what a person shapes things with, the particular talent they put form on. Five is the number of making. A tight conjunction in the fifth harmonic often describes a skill a person has always had and never thought worth mentioning, because to them it is simply how things are done.

The seventh harmonic shows inspiration and longing: the imaginative or romantic pull, the things a person is drawn towards without being able to justify them. Seven does not divide the circle neatly, and the seventh harmonic has a matching quality: it describes what moves a person rather than what they can explain.

The ninth harmonic shows what a person is drawn to as meaning. It is the tropical cousin of the navamsa, the ninth divisional chart of Indian astrology, which is read for marriage and for what a life is ultimately for. Of the three, it is often the one that speaks most plainly.

Other harmonics exist and some astrologers use dozens of them. These three are where most of the useful reading is, and they are the ones the report calculates.

What the report shows

You choose the harmonic, and the report shows where every planet and the North Node falls in that harmonic chart, draws the harmonic chart as a wheel of its own, and lists its conjunctions, closest first. Those conjunctions are the point of the whole exercise.

The orb matters here. Multiplying a position also multiplies any distance between positions, so an orb that sounds modest in a harmonic chart is very tight in the birth chart. Our report counts two planets as conjunct when they are within ten degrees of each other in the harmonic chart. Back in the birth chart, that means the original aspect was exact to within about two degrees in the fifth harmonic, about one and a half in the seventh, and a little over one in the ninth. Those are the usual orbs for a quintile, a septile and a novile. Each conjunction is shown with both orbs, so you can see how close the original aspect really was.

This tightness is deliberate. With a looser orb, the fifth harmonic would list pairs that happened to land near each other by chance, and with eleven points there are fifty-five possible pairs. A list of everything is not a reading.

How to read a harmonic chart

Read it for its conjunctions and close groupings, and almost nothing else. The question to ask is always: which planets has this number brought together? Then take that pair back to the birth chart and ask what they mean there, together.

Suppose the fifth harmonic joins Mercury and Neptune. In the birth chart they make only a quintile, easy to overlook, but the fifth harmonic says that the combination of thinking and imagination is part of how this person makes things. In practice that might look like a writer of strange, vivid stories, or an engineer whose best ideas arrive as pictures. Suppose instead the ninth harmonic joins Venus and Saturn: love and meaning are bound up with commitment, patience and duty, and the person may take a long time to choose and then choose for good.

Do not read the signs and houses of a harmonic chart as statements in their own right. They are a by-product of the multiplication, and they shift wildly with small changes in the original positions. A planet "in Taurus" in the fifth harmonic is not saying anything about Taurus. It is the grouping that carries the meaning.

And notice that a planet that makes no conjunction in any of the three harmonics is not missing anything. It simply speaks through the ordinary aspects of the birth chart.

Why the birth time matters less, and more

The planets other than the Moon move slowly, so an approximate birth time is enough to harmonise them. The Moon moves faster, and its harmonic position shifts more. The Ascendant and Midheaven are a different matter altogether: multiply an uncertain angle by nine and the uncertainty is multiplied by nine as well. That is why our report works with the planets and the Node and leaves the angles out of the harmonic conjunctions.

To see what your chart says beneath its ordinary aspects, open your harmonic charts here. Start with the fifth and the ninth, look at which planets come together, and take each pair back to your birth chart.

Frequently asked questions

What is a harmonic chart?
The birth chart with every position multiplied by a chosen number and brought back onto the circle. Aspects belonging to that number become conjunctions, which makes them easy to see and to judge.

Which harmonics does the report show?
The fifth (creativity and craft), the seventh (inspiration and longing) and the ninth (meaning, and what a person is drawn to). Start with the fifth and the ninth.

Are the signs and houses in a harmonic chart meaningful?
Mostly not. The method is about which planets come together; the signs and houses of a harmonic chart are consequences of the arithmetic rather than statements in their own right.

Why are so few conjunctions listed?
Because the orb is tight on purpose. Ten degrees in the harmonic chart is only about one to two degrees in the birth chart, which is the usual orb for these minor aspects. A loose orb would fill the list with chance.

Do I need my birth time?
For the planets an approximate one is enough. The angles need an accurate time, because multiplying a position multiplies its error too, which is why they are left out of the harmonic conjunctions.