Starting with the chapter on how to construct a chart, the first sentence is, "Mathematically, constructing a composite chart from two natal charts is simple," what followed, left me in utter confusion. The author lets you know you can contruct these charts on a computer, but doesn't expound. The best thing I found in this book, is the form you can mail in, and have them do a chart for you.
John Townley's text is one of the leading sources for understanding composite charts. Townley came across this method of analyzing relationships in 1973 when a Mensa-member friend of his mentioned it to him in New York. He proceeded to chase down its origins to understand it better. He discovered that it was not a new technique and that "Dr. Walter Koch (of the house system) apparently knew of it back in the 1920s" (p. xviii). Townley then discovered published writings from 1919 by biologist Paul Kammerer. Townley believes that the founding concepts that explain what a composite chart is and why it works can be derived from Kammerer's theory of "imitation effect." Townley explains this theory in the chapter "Some Theoretical Groundwork" (p. 3-12). The composite chart is defined by Townley as "a horoscope made up of the mutual midpoints between the natal charts of two persons-the composite Sun is located at the midpoint between the two natal Suns, the composite Moon is at the midpoint between the two natal Moons, and so on" (p. 11). Townley reasons "the composite Sun is precisely the point at which rhythms shift over from one person to the other, and shift from relative increase to decrease and vice versa, one to another. It is really a critical, phase shifting point where one person (usually unknowingly) 'hands the ball' to the other with a mutual shift of energy and responsibility. It is a point of mutual empowerment, the swing point where one gives to the other at the most primal level" (p. 12). Hence, "just as the composite chart itself describes the subtleties of mutual empowerment, the use of the technique further empowers those involved individuals and allows them greater control over their lives" (p. 14)
I have presented excerpts from the book to help you understand the basis of how and why a composite chart works. These excerpts are important keys concepts that shed some light and understanding on the composite chart. Basically, the composite chart is the critical point between two people where a third powerful force is created, which represents the relationship. Townley explains the hows and why of the composite chart in the chapter "Some Theoretical Groundwork" (p. 3-11). When a relationship is formed it develops its own intensity and strengths, which impacts the individuals who comprise the relationship. This means that although synastry, which is another relationship analysis method, may be quite good between two people, the composite chart suggests the kind of relationship produced when two people come together. In other words, the composite describes what the couple undergoes within the relationship and sheds light on how they can cope with it.
Townley's book is geared overall towards understanding relationship dynamics. The first few chapters explain Townley's belief of the scientific groundwork on which the composite chart is based. The rest of the book discusses the composite chart and its key components elucidating how it works. All in all, this is an excellent book to own because it is a comprehensive survey. However, as with all books that cover a lot of ground, it presents comprehensive generalized meanings. In other words, it is not all-inclusive but it includes the most important key points that you should know. This text therefore makes a good starting point for those who take the time to read it in its entirety. I did not find his scientific explanations too difficult to follow, but I would recommend reading it more than once and to truly understand it, because when you do, then you'll understand why the composite chart is so powerful. The Scientific part is in the first chapter or so, and the proceeding chapters cover interpretations, which are Townley's suggestions on how you can read the chart symbolically. Having said that, I will also add that after 25 years of practicing astrology and relationship analysis, it takes a while to really understand how to read and interpret any astrological chart. The reason is that it takes a while to understand what the individual aspects mean, and then to understand what the sum total of all the aspects represents and what it's trying to tell you. Astrology takes time to know. Fortunately, with practice it gets easier. Some math skills will be needed, if you erect a chart by hand. Otherwise, you may want to take advantage of computer programs to help you erect a chart. Many programs are free of charge and can be downloaded at such sites as zdnet or tucows; just type "astrology" in their search engines. Townley's book is a fabulous starting point, especially if you read his book in its entirety.