Solar arc directions are one of the most used predictive techniques in Western astrology. The premise is simple: every year of life, every planet in the natal chart advances by approximately one degree. At age 40, every planet has moved roughly 40° forward from its birth position.
The system shows how natal energy matures over time. A natal Mars in Aries at 10° will be at Solar Arc Mars in Taurus 0° at age 50 — the drive and initiative energy (Mars) has shifted from self-starting Aries into Taurus, taking on more patience and deliberation.
Astrolium's solar arc directions calculator advances every natal planet, house cusp, and angle by the same arc as the secondary-progressed Sun, roughly one degree per year of life, and reports the directed positions plus active aspects to the natal chart on a target date. The tool accepts birth date, time, and place along with the date to project to, then returns each planet's directed longitude, sign, and any conjunctions, squares, or oppositions within a 1° orb to natal placements. The Directed Sun section is the centrepiece, with sign-change events flagged as identity shifts. Practitioners use it as a slower, simpler companion to secondary progressions and transits, since solar arc aspects stay active for roughly two years and describe sustained developmental themes rather than daily events. Calculations use Swiss Ephemeris with sub-arcsecond accuracy. Free, no account required.
Reading your directed chart
The interpretation sections focus on which directed planets are currently making significant aspects — conjunctions, squares, oppositions — to natal planets. These represent the themes most active right now.
The Directed Sun section is the centrepiece, as it carries the most concentrated energy. When the Directed Sun changes signs, it often coincides with a significant shift in identity and purpose.
Solar arc timing
Unlike transits, which last days or weeks, solar arcs are slow-moving. A conjunction within 1° will be active for roughly two years. The interpretations are therefore less about specific events and more about sustained developmental themes.
Compare your solar arc picture with current transits and secondary progressions for a complete timing picture. Solar arcs describe the terrain; transits describe when to act.