Vertex

The Vertex is a calculated point of the chart, the intersection of the prime vertical with the ecliptic in the western half of the sky. Unlike the four angles it is a modern addition to astrological technique, introduced by the American astrologer L. Edward Johndro in the late 1920s and 1930s in the course of his research into what he called the electric ascendant, a separate concept built from the same prime-vertical geometry.

Johndro shared his findings with fellow astrologer Charles Jayne, who tested the point through the 1940s and 1950s by running solar arc directions to it and concluded that the point opposite Johndro's original construction responded more reliably in practice, and it is this opposite point, in the chart's western hemisphere, that became established as the Vertex proper. The point directly opposite it in the eastern hemisphere is called the Antivertex, and the pair is sometimes read together as an axis. Johndro laid out the underlying theory in two books published in 1929, "The Earth in the Heavens" and "The Stars: How and Where They Influence," where he framed the electric ascendant within what he called a GEM field theory of gravity, electricity and magnetism, an idiosyncratic framework largely abandoned by later astrologers even as the geometric point it produced went on to independent use.