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Charts & data › Davison chart

Davison Relationship Chart

Find the moment halfway between two births and cast a new chart at the geographic midpoint. This version follows the shortest route across the globe, including across the date line.

STAR & SIGIL

Create your birth chart

Star & Sigil birth chart tools

Two birth records

Use each recorded local clock time and the historical UTC offset in effect at that birthplace. Both times and both places are required.

Person A
Person B

Offset is hours east of UTC, including historical daylight saving. Check dates, coordinates, and offsets before reading angles or houses. Look up a birthplace →

How this chart is made

Each local birth time is converted to UTC. The chart time is exactly halfway between those two instants. We locate the place halfway along the shortest great-circle route between the birthplaces, then calculate a new tropical chart for that time and place.

Davison charts can use several midpoint variants. This page uses the spherical midpoint place method. The uncorrected method averages latitude and longitude separately, so the two can produce different houses. Very close to antipodal birthplaces, the spherical midpoint is unstable and this calculator asks you to use another method. A midpoint near a pole can also leave local angles or houses undefined.

Planetary and house calculations use Astronomy Engine 2.1.19 through this site’s natal chart engine. This chart describes a calculation tradition; it does not predict relationship outcomes.

Method and limits

Two time records

Enter both local birth dates and times with the historical UTC offsets that applied at each birthplace. The tool converts them to UTC before finding the exact halfway instant. A bad offset shifts the midpoint and its chart, so check daylight-saving rules for both birth dates.

Spherical place method

The midpoint place lies halfway along the shortest great-circle route. This is one documented Davison variant. The uncorrected coordinate-average variant can place the chart somewhere else, especially across the date line. Very near antipodal birthplaces have no stable unique spherical midpoint and the calculator rejects them.

Reading the result

The tool calculates a fresh tropical chart at the midpoint instant and location. It displays the Ascendant, Midheaven, twelve house cusps, planetary positions, and the selected house system. The chart is a calculation convention for comparing records; it does not measure or predict a relationship.