A midpoint composite pairs A’s Sun with B’s Sun, A’s Moon with B’s Moon, and so on. For each pair it locates a halfway point along the shorter zodiac arc. The resulting degrees do not depict the sky at a third birth or meeting. They form a symbolic chart of the relationship.
A worked midpoint example
Imagine A’s Sun at 10° Aries (longitude 10°) and B’s Sun at 20° Gemini (80°). The 70° shorter arc has its midpoint at 45°, or 15° Taurus. Imagine A’s Moon at 20° Cancer (110°) and B’s Moon at 10° Virgo (160°). Its midpoint is 135°, or 15° Leo. The two derived positions are exactly 90° apart: a composite Sun–Moon square. These are invented degrees to demonstrate the arithmetic, not a reading of real people.
| Point | Person A | Person B | Short-arc midpoint |
|---|---|---|---|
| Sun | 10° Aries · 10° | 20° Gemini · 80° | 15° Taurus · 45° |
| Moon | 20° Cancer · 110° | 10° Virgo · 160° | 15° Leo · 135° |
| Composite aspect | 135° − 45° | 90° square | |
At a zodiac boundary, use the shorter circular arc rather than averaging printed numbers blindly. For example, 25° Pisces is 355° longitude and 5° Taurus is 35° longitude. Their midpoint along the 40° route across 0° Aries is 15° Aries. A plain numerical average would point to the wrong side of the circle.
Read the composite as a pattern of the pair
In this invented chart, the Taurus Sun and Leo Moon are square. An astrologer might use that geometry to ask how a wish for steadiness and visible emotional expression share space in the relationship. The chart does not identify which person is “the Taurus” or “the Leo.” Both contributed to both points. Return to the natal columns and to synastry to see how each individual might experience the pattern differently.
Begin with the exact degrees, then the main composite aspects, then the Sun and Moon as organizing symbols. A short list of close contacts is easier to examine than every line in a dense wheel. Keep a note of any midpoint exactly 180° from its matching partner point: two opposite midpoints are equally short, so the convention must be stated. The site's composite calculator surfaces such ambiguity instead of silently presenting one answer.
The combined composite and natal drawing puts all three charts on one page. Use it to check whether a composite claim depends on a specific natal contribution. The clickable partner chart offers a smaller interactive view of the measured factors.
Houses are a separate method choice
Composite planets can stay fixed while the house frame changes. One method takes midpoints of corresponding natal cusps. Another starts from a composite Midheaven and a reference latitude, then derives a new set of cusps. They are different constructions, and the same planet may move from one house label to another. Compare the house-method calculator before attaching meaning to such a difference.
If a birth time is missing, an accurate natal Ascendant and house grid cannot be recovered from the date alone. A composite with confidently named houses would imply information the source record does not provide. A midpoint composite is distinct from a Davison chart, which calculates positions for a derived time and location. The two charts need separate method labels.
No composite factor can demonstrate compatibility, consent, or a future event. An interpretation is most useful when it produces a fair question that both people can accept, revise, or reject.