How to tell a chart is wrong

Run four checks that catch most bad charts in ten seconds, and recognise the one common error that no check can catch.

Lesson 6 of 6 in Casting a Chart · free to read · no account, no email

Four checks, ten seconds

Before you read a word of a chart, look at it as a piece of data and ask whether it can possibly be right. Four checks catch nearly everything, and they take about as long as reading this sentence.

One: does the Sun match the date? If the birthday is in late July the Sun is in Leo, give or take a day at the edges. A Sun in the wrong sign means a wrong date, a calendar problem, or a typed year.

Two: are Mercury and Venus near the Sun? They have to be. Mercury never gets more than about 28° from the Sun and Venus never more than about 47°, because their orbits are inside ours. Mercury three signs from the Sun is not an unusual chart; it is a broken one.

Three: is the Moon's daily motion plausible? Between about 11.8° and 15.4° a day. Anything outside that range means the date or the interpolation is wrong.

Four — the best one: does the Sun sit where the time of day says it should? At sunrise the Sun is near the Ascendant. At noon it is near the Midheaven. At sunset, near the Descendant; at midnight, near the IC. A chart for a two-in-the-afternoon birth with the Sun at the bottom of the wheel has a twelve-hour error in it, and this check finds every AM/PM mistake ever made in about a second.

What each kind of error looks like

Errors have signatures, and learning them turns “this chart feels off” into a diagnosis.

A twelve-hour error — the classic AM/PM slip — puts the Sun on the opposite angle and rotates every house by roughly half the wheel. The planets are all in the right signs, so nothing looks obviously wrong until you apply check four.

A wrong year leaves the Sun in nearly the right place, because the Sun returns to almost the same degree each birthday, but the Moon and every other planet are somewhere else entirely. A chart where the Sun looks right and nothing else makes any sense is almost always a mistyped year.

A calendar error, for old dates, moves everything by about ten to thirteen days: the Sun is in the right sign but the wrong degree, and the Moon is a third of the way round the chart.

A flipped hemisphere — a latitude or longitude entered with the wrong sign — produces a chart that looks entirely plausible and is completely wrong. There is no internal check for it. The only defence is reading the coordinates back: is this birthplace really at 51° north?

And then there is the one that passes everything. A missed daylight-saving hour leaves every planet in the right sign and degree, leaves the Sun in a perfectly reasonable relationship to the time of day, and puts every house cusp fifteen degrees out. No check in this lesson catches it, because nothing about the chart is impossible. The only defence is the zone history, which is why the last module spent a whole lesson on it.

Record the doubt, out loud

The professional habit is not certainty. It is writing down where the data came from and how much you trust it, and saying so when you read.

There is a long tradition of rating birth data by source, and it exists because astrologers were tired of arguing about charts built on a half-remembered anecdote. The categories are obvious once stated: a time copied from a birth record is one thing; a time the person's mother remembers is another; “sometime in the evening” is a third; and a time rectified from events is a fourth and must always be labelled as such, because it was produced by interpretation rather than observed.

Three sentences cover it in practice, and they are worth having ready. “Your time came from a birth certificate, so the houses are solid.” “Your time is remembered to the nearest half hour, so I will read your Rising sign but not your rising degree, and these two placements could go either way.” “We do not have a time, so I will read the chart without houses — the planets and aspects are all solid, and the Moon's sign is safe unless you were born near a sign change.”

That last one matters more than people expect. A chart with no birth time still has every planet, every aspect and every sign. What it loses is the houses, the angles and the exact Moon. A great deal can be read without them, and saying that plainly is far better than guessing noon and quietly presenting a fiction.

What that looks like

A chart arrives with the Sun in the fourth house for a birth recorded at 2:15pm. Everything else looks normal: Mercury is close to the Sun, the Moon's motion is sensible, the Sun's sign fits the date. But at quarter past two the Sun should be high in the sky, near the Midheaven, and instead it is at the bottom of the wheel — where it belongs at two in the morning. Nothing about the planets is wrong. The clock was read as AM, and check four found it before a single word of interpretation was written.

What to take away

• Four fast checks: Sun matches the date, Mercury within 28° and Venus within 47° of the Sun, Moon's daily motion 11.8–15.4°, and the Sun near the angle the time of day implies.
• Errors have signatures: a 12-hour slip flips the Sun to the opposite angle; a wrong year leaves the Sun right and everything else wrong; a calendar error moves everything ten to thirteen days.
• A missed daylight-saving hour passes every check, because nothing about the resulting chart is impossible. Only the zone history catches it.
• Record where the birth time came from and how much you trust it, and say so in the reading. A chart with no time still has every planet, every aspect and every sign — it loses the houses, the angles and the exact Moon.

The common mistake

Quietly casting a chart for noon when no birth time is known, then reading the houses anyway. The planets are real and the houses are an invention, and a reader who is not told cannot tell the two apart.

Try it on your own chart

Run all four checks on your own chart right now, then on the charts of two other people you have saved. It takes under a minute each. Then look up where your own birth time came from — certificate, memory, or family story — and write that down beside the chart. That note is the single most useful thing you can attach to a chart, and almost nobody does it.

Check yourself

The same questions the lesson asks in the app. Open one to see the answer.

Keep going

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