ORIGINAL VISUAL GUIDE
Birth chart anatomy, annotated.
A natal chart layers several different kinds of information into one wheel. This diagram shows where each layer belongs and separates calculated positions from astrological interpretation.
The five layers of a chart wheel
Zodiac ring
The outer 360° circle is divided into twelve 30° tropical signs. Planetary longitude identifies a planet's position on this ring.
Houses
The inner twelve sectors describe areas of life in astrological practice. Their cusps depend on time, place, and the selected house system.
Angles
The Ascendant and Midheaven anchor the local horizon and meridian. They are especially sensitive to birth time and location.
Planet positions
A glyph marks each calculated longitude. The sign position is astronomical output; its interpreted meaning is tradition-based.
Aspect lines
Lines connect selected angular separations between planets. The aspect type and allowed orb must be stated rather than inferred from color alone.
How the layers are calculated
Planetary longitudes are calculated for a moment in time. Angles and house cusps additionally require geographic coordinates and local sidereal time. Roho uses the Swiss Ephemeris calculation system and stores the chart result separately from interpretive prose.
When birth time is unknown, planet sign positions may still be usable within stated limits, but the Ascendant and houses should not be presented as exact. The Moon may also cross a sign boundary during the date. See Roho’s methodology and the astrology glossary.
Sources and scope
- Swiss Ephemeris documentation — ephemeris calculation scope and provenance.
- U.S. Naval Observatory: celestial coordinate systems — astronomical coordinate context.
Astrological meanings for houses and aspects are conventions within astrology and are not established astronomical findings.
Calculate and explore a birth chart