Why composite house methods disagree
A composite chart places each planet at a midpoint between two natal longitudes. It is a symbolic construction, not a snapshot of the sky on a third date. The planet positions in the two columns above are identical. The choice of house method changes the house frame around them: where the Ascendant and twelve cusps fall, and therefore which house contains a planet.
Reference place: rebuild the houses from one Midheaven
This method first takes the short-arc midpoint of the two natal Midheavens. A reference latitude then supplies the horizon geometry. For each selected house system, the calculator solves an orientation with that composite MC and calculates a new Ascendant and twelve house cusps. In this calculation the reference location's latitude matters; its longitude does not. A reasonable reference is a location central to the relationship, but there is no uniquely correct place.
Changing the reference latitude can move the Ascendant and house cusps while every composite planetary longitude remains the same. This is useful when comparing how a relationship might be framed at different places, but it is an interpretive convention. The virtual clock used to solve the orientation is only a computational aid. It is not a birth time and it is not used to produce the planets.
Cusp midpoints: average each natal boundary
The alternate method gives every house cusp its own midpoint between the corresponding cusps of the two natal charts. It also takes the midpoint of the two natal Ascendants. It does not need a reference location. These averaged boundaries can differ substantially from a fresh set of houses derived from the composite MC. They are not guaranteed to form a physically possible house geometry; this page checks their zodiac order before assigning planets to them.
Both columns use the same chosen natal house system. If a requested system is unavailable near a polar latitude, the chart engine may show Porphyry cusps instead and report a notice. An exact 180° separation between two matching natal positions has two equally short midpoints. The calculator presents both candidates rather than silently selecting one, and withholds house assignments where the cusp grid is indeterminate.
Reading the comparison
The first table shows each house's two cusps and the shorter angular gap between them. The second keeps each composite planet fixed and shows its house under each method. A planet close to a cusp can shift houses after a small change to a recorded birth time or historical UTC offset. Enter the offset that applied at each birthplace on each birth date, including daylight saving time; this page does not infer old legal time-zone rules.
Composite interpretations are subjective and cannot measure compatibility, consent, safety, or the future of a relationship.