Davison chart calculator

What a Davison chart is

The Davison relationship chart is named after the astrologer Ronald Davison. Instead of averaging the planets one by one, as a composite chart does, it averages the two births themselves: the midpoint in time and the midpoint in space. Then it casts an ordinary chart for that moment and place.

If one person was born in Paris in July 1990 and the other in New York in November 1988, the Davison moment falls in September 1989, at a point in the middle of the Atlantic between the two cities. Every planet in the chart is where it really was at that moment, so the Davison chart is a sky that existed, not a construction.

How the midpoint is found

The midpoint in time is the average of the two birth moments in Universal Time, so time zones and daylight saving time do not affect it. The table under the result shows the gap between the births and the exact midpoint moment.

The midpoint in space can be found two ways, and the form lets you choose:

• Average of latitudes and longitudes (the default and the classic method): add the two latitudes and halve them, then the same for the longitudes, taking the shorter way round the date line.
• Great circle midpoint: the point halfway along the shortest path between the two birth places on the globe. For two places in the same hemisphere that are far apart east to west, it lies closer to the pole than the simple average.

For couples born close together the two methods give nearly the same place. For births on different continents they can be hundreds of kilometers apart, which changes the Ascendant, Midheaven and houses but not the planets' signs.

How to read your Davison chart

Astrologers read a Davison chart like a birth chart, applied to the relationship as a unit. The Sun shows what the bond is for, the Moon its emotional tone, Venus how affection flows, Mars how the two of you act together and argue, and Saturn what the relationship takes seriously. The Ascendant, with both birth times, describes how the couple comes across.

Because the Davison chart is a real moment, it can also be used for timing: astrologers follow transits to it the way they follow transits to a birth chart. The readings under the chart are our birth chart readings of each placement, so read "you" as "the two of you".

The Davison relocation map

Since the Davison chart is a real sky, it has real astrocartography lines, drawn exactly like your own: where each planet was rising, setting, overhead or underfoot at the midpoint moment. The marked point is the midpoint place. Astrologers who use relationship maps read a place near the Davison Venus or Jupiter line as one where the relationship's warmth comes forward, and a place near its Saturn or Pluto line as one that asks more of it.

Choose a theme to list the large cities near the matching Davison lines, tap any place to read its nearest lines, and see where the lines run near each of your birth places. To compare, the composite map draws the lines of the midpoint chart, and the synastry map puts both of your own maps on one globe. A line is one input among many, never a reason on its own to move.