How a chart is made

A map of one moment

A birth chart is a map of the sky at the moment you were born, seen from the place you were born. It shows where the Sun, the Moon and the planets were, against the twelve signs.

The circle is divided into twelve houses. The line on the left is the eastern horizon, where the first house begins. That point is your rising sign. The top of the chart is the Midheaven, the highest point of the sky, where the tenth house begins.

The houses and their cusps

The line where one house begins is called its cusp. Each cusp falls in a sign, and that sign colours the house.

In the old method you worked out six cusps from a printed table, and the other six took the same degrees in the opposite signs. Only once in a while do the signs fall neatly on their natural houses, Aries on the first, Taurus on the second and so on. Most charts mix them up, and that mix is part of what makes each chart its own.

The cusps move quickly through the day. Without a reliable birth time, the old astrologers said, you cannot use them well.

Placing the planets

Astrologers used a yearly book of planet positions called an ephemeris. It listed where each planet was at noon in Greenwich, England, every day.

To draw a chart you turned the birth time into Greenwich time, allowed for summer time if it was in force, and worked out how far the Sun and the fast-moving Moon had travelled since noon. The slower planets were placed almost as listed. Then each one went into the house its degree fell in.

The old table of rising signs

The 1927 book printed a long table so readers could find their own rising sign. It gave the rising sign for each hour of every fourth day of the year, worked out for places around 41 degrees north, about the latitude of New York. For anything in between, you estimated.

It came with a list of the years summer time had been in use, so readers could take the extra hour off.

The author also remembered her own teacher saying that the people who fuss over every minute rarely become good chart readers. The numbers matter. The understanding matters more.

How charts are worked out today

Today a chart is worked out with astronomy formulas instead of printed tables. The birth place gives the latitude and longitude, and the date and place together tell you which time zone and which summer-time rules applied.

There are several ways to divide the sky into houses, and astrologers still disagree about which is best. The 1927 book used the tables most English astrologers used at the time.

Sit with this

Your chart is a picture of the sky the moment you arrived. It is a starting point, never a sentence.

I read it the way I read the cards. It shows energy and patterns. What you do with them is yours.