← Encyclopedia of Astrology · lesson 206/235
Solar arc
What it is
Solar arc directions take the whole birth chart and turn it forward as one piece. Every planet and angle is advanced by the same amount — the solar arc — and the directed positions are then compared with the natal ones. Where a directed point comes to an aspect with a natal point, that year is marked.
How it is computed
The arc comes from secondary progression. Find the progressed Sun for the date (one day after birth for each year of life) and measure how far it has moved from the natal Sun. That distance is the solar arc. Because the Sun moves a little under or over a degree a day depending on the time of year, the arc is close to one degree per year of life — about thirty degrees at thirty — but not exactly.
Add that arc to every natal point: the Sun, the Moon, the planets, Chiron and the Node, the Ascendant and the Midheaven. Everything keeps its natal spacing; the chart has simply rotated. Bernadette Brady describes it as turning the top chart at the rate of the progressed Sun.
Which contacts count
A solar arc reading looks for directed points making these aspects to natal points: the conjunction, sextile, square, trine and opposition, plus the semisquare and sesquiquadrate, the 45° family that is often eventful in directions. The allowance is tight — about one degree — because one degree of arc is about one year: a directed contact within a degree is treated as active for that year, and is most marked as it becomes exact.
How it is read
Because every point moves at the same speed, a solar arc can bring a slow planet's influence to a natal point at a pace transits never would: directed Saturn reaching the natal Sun, or the directed Midheaven reaching natal Venus, once in a lifetime and for about a year. Solar arcs are read as markers of significant years, best taken together with transits and progressions. They describe when a theme tends to come forward, not what must happen.