A map of the sky at the exact moment and place you were born.
A natal chart is a snapshot. Give it a date, a time and a point on the Earth's surface, and it records where every body was against the zodiac at that instant. Nothing about producing one is mystical: it is the same calculation an observatory would run to point a telescope.
How to read the grammar
A chart is built from four kinds of thing, and they combine like parts of speech. Once you have the grammar, most of a chart reads itself.
| Element | Part of speech | Answers |
|---|---|---|
| Planets | Verbs | What is happening |
| Signs | Adverbs | How it happens |
| Houses | Nouns | Where in a life it lands |
| Aspects | Conjunctions | How two parts of you get along |
So Mars (the part of you that takes action) sitting in Gemini, the sign of curiosity and scatter, reads as: you take action curiously, restlessly, several things at once. Put that in the tenth house and it is happening in your career. Same verb, different manner, different room.
Why the time matters so much
Your planetary positions barely move over the course of a day. The Moon is the exception, covering about half a degree an hour. But the houses and the rising sign depend on the Earth's rotation, which turns the entire chart through a full circle every twenty-four hours. Two people born the same day in the same city have nearly identical planets and completely different houses.