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The Birthchart as a Map: Part 4 of 12
by Mary Plumb

What is it about the birth chart that so intrigues the student of astrology? Many of us have been drawn into the study of astrology by an almost irresistible fascination with the glyphs and symbols of the chart. Let us begin decoding the map by looking at the simplest structures of the chart, the circle and the cross, to see what cosmic terrain they may represent.

When looking at a birth chart, it is essential to understand that the chart or map is describing a picture from the Earth-centered (geocentric) point of view.

Although astrologers, of course, know and understand that the Sun is the center of our solar system (heliocentric), we are observing the planets and other celestial phenomena from our view on Earth where human life occurs. The horoscope (map of the hour) is a drawing from our viewpoint on Earth of the position of the planets and zodiacal signs from a particular place at a certain moment in time. Natal astrology is the study of the birth chart of the person (or business or event, etc.) born at a certain time and calculated for the exact time and place of birth.

Looking at the most basic structure of the birth chart, surrounding and supporting the planets, we see a circle with a cross inside (see Fig. 1). The circle of the chart depicts the 360 degrees (360°) of the band of the zodiac. This band is composed of the 12 signs of the zodiac, from Aries to Pisces, which are 30° each. This wheel of the zodiac (circle of the animals) is derived from the motion of the Earth in a broad circular path around the Sun during the course of the year. This pathway is called the ecliptic. Since we are considering the Earth as center, the Sun, Moon, and planets appear to travel along the 360° pathway, within 8° on either side of the ecliptic (or, in the case of Pluto, 17°), which is then divided into 12 equal segments of 30° each, relating to the constellation of the same name. (I have just described the tropical zodiac, widely practiced in Western astrology. See #1 of our Beginner's Series for a definition of the sidereal zodiac.) The 12 signs of the zodiac describe the process of complete human evolution – all possibility is contained within the circle of infinite spirit.

This zodiacal belt is the circle that surrounds all astrological charts and provides the background through which the planets travel. The constellations of the zodiac remain in the same positions relative to one another, and the planets wander constantly around the 360° wheel. This picture of the planets' positions in relationship to the background of the zodiacal belt is what is shown in the map of the birth chart.

The circle of the zodiac is thus descriptive of the Earth's annual passage around the Sun, but we are also concerned with the daily rotation of the Earth on its own axis (diurnal rotation). Due to the Earth's rotation on its axis every 24 hours, the wheel of the zodiac makes a complete turn each day moving in a clockwise direction. Although a circle symbolically has no beginning or end, in the astrologer's view the birth moment and place describe the entry onto the wheel of life. This beginning point is always on the left side of the chart and is called the Ascendant or Rising Sign. This is east of the place and time of birth and is the exact degree of the 360° wheel that crossed the eastern horizon at the moment and place of birth. It marks the intersection of the ecliptic with the horizon, or the meeting point of heaven and Earth. Due to the diurnal rotation, the complete wheel of the zodiac will cross over the Ascendant every 24 hours. In fact, there is a new degree on the Ascendant approximately every four minutes of time.

The horizontal line in the center of the wheel depicts the horizon, which extends from the Ascendant in the east across the circle to the Descendant or western point. The vertical line of the cross is called the meridian and shows due south (the top of the wheel) at the moment of birth, and due north, the very bottom of the chart. The cross (a.k.a. the astrological angles) represents physical manifestation, Earthly life, the meeting of Divine intent in Earthly form.

When looking at a birth chart, any planets drawn above the horizon will be overhead in the sky at birth, while planets drawn below the horizon are under the Earth at the particular time and place that the chart describes.

Looking at Fig. 1, we can see that for a birth at dawn, the Sun will be near the Ascendant or eastern point of the chart. The Sun's travels from east to west during the 24 hours of the day are mirrored in the chart by its clockwise movement to the top of the chart, the MC (medium coeli) or Midheaven, which is due south at the moment of birth. Any chart for a person or event born around noon will have the Sun placed near the top. Directly across from the Ascendant is the Descendant or western point in the sky. Births occurring around Sunset will have the Sun placed in the West or near the Descendant of the chart. As the Sun sets in the sky, it travels down clockwise toward the bottom of the chart, the IC (imum coeli) or lowest heavens. This represents midnight, and a person born around this time will have the Sun near the bottom of the chart, also due north. As we approach morning after midnight, the Sun continues in a clockwise movement until dawn, when it rises above the horizon and is again visible in the eastern sky or near the Ascendant of the chart. You can check the accuracy of any chart by verifying that where the Sun falls in the chart reflects the actual hour of the birth time. (For example, if the birth is at 6:00 a.m., and yet the Sun is near the top of the chart, or MC, you will know there is an error.)

The horoscope is a diagram of the celestial world and where we intersect with that world. The simplest structures, the circle and the cross, can begin to orient us to the profound truths of astrology and help us to see the horoscope as a map of both inner and outer terrain.


Jeff Mayo, The Astrologer's Astronomical Handbook; L.N. Fowler & Co., Essex, England. First edition: 1965. Most recent edition: 1982. May be hard to find, but it is a gem.

Alan Oken, Complete Astrology ; Bantam.

Robert Hand, Horoscope Symbols; Para Research, Gloucester, Mass, 1981.



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