PRACTICE / 31 OF 36
Compare Two Charts
By the end you can compare two charts in one fixed order, and you will know why saying the differences clearly is more useful than a compatibility score.
Approved original lessons, free on the web · 2026-10-12
THE IDEA
Your task: compare two charts in one order, and write down only where they differ.
Diagram: an outer ring labelled Sun, an inner ring labelled Moon, and a point at the bottom labelled Ascendant, stacked on one vertical line to show three different layers rather than real degrees.
Compare one layer at a time, never all mixed together.
The order to compare in
Compare two charts in the same order you read your own: Sun first, then Moon, then Ascendant. For each layer write only “same” or where they differ, and save any conclusion until all three layers are done.
Reflection promptThe Sun is the direction a person faces outward, the Moon is how they settle themselves, and the Ascendant is how they walk into a room. When you compare, turn the three layers into three questions: where are they heading? How do they settle themselves? How do they walk into a new place?
Later interpretationCompare Ascendants only when both people have an exact birth time. If either one is missing it, skip straight past this layer and compare the Sun and Moon, so the whole comparison rests on solid data.
Reflection promptWhat the old texts say: Book III ch. 13 of Ptolemy's Tetrabiblos says the impulses of the soul vary a great deal, so they need many observations together, never a simple or offhand judgement.
Cited sourceComparing two charts is for saying clearly how two people differ.
Compare differences, not scores
When you finish comparing two charts, you hold a list of differences: Sun, Moon and Ascendant, one line each on where the two people are the same and where they differ. A relationship is something two real people live out together, and this list helps you understand each other and start talking more easily.
Reflection promptThe useful part of comparing two charts is that it helps you say something specific, like “the way I settle is not the way they settle.” Being able to say the difference is worth far more than a score.
Reflection promptWhat the old texts say: Book IV ch. 5 of the Tetrabiblos is the marriage chapter, and it opens by looking at the Moon in men's charts and the Sun in wives'.
Cited sourceOBSERVE YOUR OWN CHART
Look at my chart
Your turn: use the data of someone who has agreed, or practise on the demonstration placements.
- Ask before using anyone's birth data, and enter a time only when it is certain.
- Compare Sun, Moon and Ascendant one layer at a time, one line of difference each.
- Write one line: which layer's difference really shows up between you most often?
Without a birth time, rising sign and houses stay blank.
LOOK CLOSER
A common mix-up
“A compatibility table shows whether two people fit.”
Comparing charts is for saying the difference clearly, such as how each person settles themselves; how well two people get on shows in their life together.
“They don't remember the hour, but a rough guess is good enough for the Ascendant.”
The Ascendant changes sign about every two hours on average, so it needs an exact time to be right. Without one, just skip that layer.
CHECK YOURSELF
Now, try it yourself.
Sources and rights
- Ptolemy, Tetrabiblos, trans. F. E. Robbins (Loeb Classical Library, 1940)
Book III ch. 13 says the impulses of the soul vary greatly and such inquiry needs many complicated observations rather than a simple approach; Book IV ch. 5 opens by observing the Moon in men's charts and the Sun in wives', and only that fact is cited, with the chapter's framing of gender and marriage not carried over. The layer-by-layer order is this lesson's arrangement, and scoring no match is this app's choice, with the reason stated.
The Robbins translation is in the public domain, as the University of Chicago LacusCurtius copyright page records. The transcriber's own notes and layout are not cited. · 2026-10-10
Limits of this lesson
Comparing two charts is a language for describing how two people differ, not a prediction; whether they get on, or stay together, shows in their life.
When one side has no birth time, that chart has no Ascendant, and a rough guess or noon should not fill it in; skip that layer and compare the Sun and Moon.
The two demonstration sets are not real people and use no real birth data.
YOUR STUDY
Write what you learned in your own words.
Write it down: the three differences you found, and which one shows up most in daily life.
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