Composite chart

Davison chart

A Davison chart is an alternative relationship chart, calculated not from mathematical averages of planetary positions (as in a composite) but for the actual date, time and place exactly halfway in time and space between the two people's births.

The advantage of this method is that the resulting chart corresponds to a real moment in time (not a purely mathematical point), so it can be used to calculate things like transits — much like an ordinary birth chart.