This drawing places two calculated natal charts beside their derived midpoint composite in one wheel. The outer ring belongs to Person A, the middle ring to Person B, and the inner ring to the composite. The positions and drawing here are independently calculated and laid out; degrees can differ from a Swiss Ephemeris output.
What is averaged
For each matching planet, the calculator measures the shorter arc around the tropical zodiac and places the composite point halfway along it. The two natal Ascendants, Midheavens, and matching house cusps are treated the same way. This is the midpoint house method. It is different from the reference-place approach, which starts with the composite Midheaven and rebuilds the house frame from a chosen latitude. The chart here asks for both birth locations because the original natal angles and house cusps need each person's geographic horizon.
Consider natal Venus at 350° and 10°: the short arc crosses 0° Aries, so its midpoint is 0°, not 180°. A pair exactly 180° apart has two equally short arcs and two candidate midpoints. Rather than silently choosing one, this tool prints both. Near opposition, a small birth-data correction can move the chosen short arc to the other side of the wheel. The result is especially sensitive for a natal Moon when a birth time is uncertain.
How to use the three rings
First inspect the two natal positions before reading their midpoint. A close composite Sun–Moon contact, for example, is made from two separate pairs of source positions. The composite is a symbolic pattern, not a sky observed at a third time. Read the colored rings by their legend and use the table for exact degrees; symbols can visually overlap when several planets occupy a small arc. The tables show every planet in both natal charts and the composite. A separate expandable table records the Ascendant-related house-cusp calculation for all twelve houses.
The thin center rays show cusp midpoint longitudes. Zodiac cusp averaging is a mathematical convention; the resulting sequence is not guaranteed to be a physically realizable house geometry. For this reason the page does not assign composite planets to numbered houses or claim that the center ring is a possible birth chart. It also leaves Mercury and Venus at their calculated positions rather than applying an optional 180° reversal sometimes used by chart-drawing conventions.
Birth records and interpretive limits
Enter each person's recorded local clock time, birthplace latitude and longitude, and the UTC offset that actually applied on that date, including historical daylight saving time. The form does not infer legal time zones from place names. A wrong offset changes natal angles and houses and therefore their midpoint results. Placidus, Campanus, or Regiomontanus may fail at extreme latitudes; the underlying house engine reports a Porphyry fallback. If the two natal charts end up using different effective systems, examine the labeled result before comparing cusps.
The wheel is a way to inspect arithmetic and astrological symbolism. It is not a relationship score and cannot determine consent, safety, or future conduct. Compare the people and their real circumstances when making decisions.
A worked wraparound example
If one planet is at 28° Pisces (358°) and the other at 2° Aries (2°), their short separation is four degrees. Their midpoint lies at 0° Aries. A plain arithmetic average of 358 and 2 would be 180°, directly opposite the correct short-arc midpoint. This is why the tool uses circular arithmetic, including for angles and house cusps.
Why the midpoint chart can look unusual
The composite does not have to obey the physical constraints of one real sky. In an actual birth chart, Mercury remains close to the Sun in ecliptic longitude; a midpoint Mercury can be far from a midpoint Sun because each was averaged from a different pair of natal positions. Some presentation styles relocate such a midpoint by 180°. This calculator prints its unaltered short-arc result, making the underlying calculation easier to audit against both natal columns.
Compare the correct method
If the question is how the chart changes at a reference place, use the separate reference-place composite tool instead. If the question is which planet from Person A contacts a planet from Person B, use synastry. If the question is what the sky looked like at a derived midpoint time and location, use a Davison chart. These are different constructions with different inputs, not interchangeable visual styles.