What is the difference between a composite and a Davison chart?

A composite averages each pair of planetary positions. A Davison chart casts a real chart for the midpoint in time and place between two births, so it describes a sky that existed.

Why can a composite chart be astronomically impossible?

Averaging positions independently can place Mercury more than 28 degrees from the Sun, which never happens. The composite is a construct, not a description of any possible sky.

Can a Davison chart be progressed?

Yes, because it has a real date, so ordinary progression and transit techniques apply. A composite has no date and can't be progressed the same way.

Davison charts vs composite charts

One is a real sky at a real moment. The other is an average of two skies nobody saw.

2 min read · Published 31 August 2026

In one paragraph

A composite chart averages the two people's planetary positions, the midpoint between each pair. A Davison chart instead finds the midpoint in time and space between the two births and casts a real chart for that moment and place. The key difference is that a Davison chart is an actual sky that existed, while a composite is a mathematical construct that never did.

The two methods

	Composite	Davison
Method	Midpoint of each pair of planetary positions	A chart cast for the midpoint date, time and place
Is it a real sky?	No, the positions never occurred together	Yes, a real moment that happened
Internally consistent?	Not necessarily	Yes, by construction
Needs birth times?	For angles and houses	Yes, and birthplaces
More common	Yes, by a wide margin	Less used

The consistency row is the substantive difference. In a composite, Mercury can end up more than 28 degrees from the Sun, which never happens in reality. The composite describes no possible sky.

Why that matters

A Davison chart reads with the ordinary rules, because it is an ordinary chart: real retrogrades, possible distances, dignity and sect as normal. A composite can't always be read that way.

Davison, if you must, because at least the moment existed. A composite chart is an average of two skies nobody saw.

How Davison works

Find the midpoint in time between the two births and the midpoint between the two birthplaces, and cast a normal chart for that moment there. Because it has a real date, it can be progressed and transited. A composite has no date and can't.

The shared limit

Neither has been shown to describe a relationship, and both exist from the moment two people were born, long before they met. AsterNym computes neither; its match compares two charts directly.

The follow-ups

What is the difference between a composite and a Davison chart?: A composite averages each pair of planetary positions. A Davison chart casts a real chart for the midpoint in time and place between two births, so it describes a sky that existed.
Why can a composite chart be astronomically impossible?: Averaging positions independently can place Mercury more than 28 degrees from the Sun, which never happens. The composite is a construct, not a description of any possible sky.
Can a Davison chart be progressed?: Yes, because it has a real date, so ordinary progression and transit techniques apply. A composite has no date and can't be progressed the same way.