A Davison chart, explained

My first client presented to me recently the situation she had of wanting to do a relocation astrology reading with her husband — together as a unit. This is a challenging situation for an astrologer to deal with, but it IS possible to do this kind of chart. It’s called a Davison chart, and it has a number of guidelines.

To begin with, it is NOT a composite chart. A composite chart just takes the two positions for each planet and averages them. So if one person has a planet at 0 degrees Cancer and another has a planet at 0 degrees Sagittarius, the composite has the planet at 15 degrees Virgo.

Two sets of planets can end up on opposite sides of the chart than originally intended. Let’s say you have one person with a 0 Sagittarius ascendant and a 15 Virgo midheaven. Let’s say the other person had a 2 Gemini ascendant and a 17 Aquarius midheaven.

The composite chart would have the midpoint of the ascendants come out to 1 degree Virgo. It would have the midpoint of the midheaven come out to 1 degree Sagittarius. So the composite chart has the midheaven three signs after the ascendant, which is unheard of unless you’re north of the Arctic Circle.

And on that level, any two planets could be ‘reversed’ like this — say I had Mercury at 1 degree Capricorn and Venus at 7 degrees Sagittarius — and you had Mercury at 1 degree Leo and Venus at 5 degrees Gemini. The midpoints would be: Mercury at 16 degrees Libra, Venus at 6 degrees Pisces. So even as the two planets are at most two signs apart in both partner’s charts, they’re nearly opposite each other in the composite chart.

If that’s not enough to tell you something about the arbitrary-ness and shallowness of a composite chart, I’m not sure what does.

The Davison chart is different. If they’re truly a unit, we take the midpoint of the two people’s birth charts — the midpoint of the two days they were born and the midpoint of the locations they were born. More on locations in a bit.

If I was born on December 10, 1969 and you were born on February 28, 1975, the midpoint would be somewhere in the neighborhood of July 19, 1975. Within a day or two, depending on the birth times. The point is to get the exactly chronologically based midpoint of the two moments in time.

Location is a bit trickier. The clients I just saw had birth locations in New York city and Boulder, CO. In their case the midpoint came to a location in Illinois. You would think that we would just average the longitudes and latitudes to get to that point. Born at 41 degrees N and 75 degrees W, averaged with 40 degrees N and 105 degrees W, we’d come up with 40.5 degress N and 90 degrees W.

You would think that was the way, but it’s not, although in this particular case the average will be pretty close to what it really is.

In fact, what needs to happen is that a great circle connecting the two points needs to be established. A great circle basically splits the planet in two and is the longest line that can be drawn around the planet, since it’s basically the diameter of the planet. Then the midpoint between those locations on the great circle is taken.

Aviators know this well. If you’re taking a plane from Taiwan (about 24 degrees N) to somewhere on the west coast of the USA, say San Francisco (about 36 degrees N), the midpoint is not at 30 degrees north in the middle of the sea. That would be a longer flight path than it needs to be, as the shorter distance between the two locations actually comes a lot closer to the Bering straight, or at least just to the south of Alaska. A great circle is created between Taiwan and San Francisco that is the shortest distance between the two locations — the direct distance.

How about you show me your flight history maps? | TravelUpdate
You can see the lines are curved, especially for longer distances. But those are exactly the shortest distances between cities.

Latitude matters a lot less in this context. If I was born at 80 or 85 degrees N, it wouldn’t matter that much if I was born at 90 degrees W or 90 degrees E — those two locations are both pretty close to each other, even though they’re opposite longitudes on the earth. You can see how averaging the longitude and latitude does not serve the partners well.

Some astrological software programs do use great circles; some do not, and it is a bit difficult to calculate a great circle in any given astrological program; it involves a good deal of math. But that’s why the lines on an Astro Map are curved, since a map is a two-dimensional image of a three-dimensional planet, particularly skewed near the poles.

Once this is done, we will have the exact midpoints between the two birth times and the two birth locations. Davison charts can be quite powerful if the two partners are truly a unit and doing things in concert with each other. Here’s a nice article from someone who has been doing Davison charts for a longer time — Corrie Cooperman.

She describes how couples whose individual charts do not particularly augur well for the location that they happen to be living in successfully in the ways that they want. She’d look at happily married couples, and for each individual’s chart she’d often find it to be an unremarkable location — not anywhere near a line, just, nowhere. Then she looked at the Davison chart and saw that it was magical.

When I do Davison charts I also look at the partners’ individual charts. There are several reasons — it’s very difficult to ascertain the durability of a union, but, more importantly, it brings us to the philosophical question of how much individuality is there for each person?

If they are truly a unit, it seems as though the indivduals have merged. And for my own personal being, that’s not necessarily how I’d want a relationship in my own life to be. Yes, there should be mutual support, always. Like many of you, I know people in successful open relationships. If there are children, of course, that does tend to merge a couple.

But the complexity and wide variety of relationships does add a layer of complexity to the procedure we’d have to use to do adequate relocation charts for those in a committed relationship. It’s not for every astrologer.

By David Muir

David Muir recieved his PAC as a 2020 graduate of the Avalon School in Vibrational Astrology. He has been a practicing astrologer having studied astrology since 1997. He specializes in relocation astrology, particularly in terms of how both one's character and external influences change in a new location. He has interests in compatibility, and just generally “getting the necessary information out there for you,” which can entail personology as well as different interpretations in general. David writes a 2x/weekly blog in both relocation astrology and other astrological topics of interest, on

David received a BA from Carlow University in 2011 with concentrations in philosophy, writing, and political science. He does a 2x/month radio show and has lived in Denver, CO since 2016.

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