About This Tool
Solar Arc and Arc Directions
Arc directions are a symbolic timing method that carries every point in the birth chart forward through the zodiac by a single, equal arc. The method's starting point is the classical "one day, one year" measure: each calendar day after birth maps to one year of life. This accumulated symbolic motion is converted into a single angle, that is the arc, and applied to the whole chart in the same amount. In this way the natal aspect skeleton is preserved intact; the only thing that changes is which directed point contacts which natal point as the entire chart is shifted forward as a whole.
The most common form is solar arc. Here the arc is taken as the angle the progressed Sun has travelled from the natal Sun. Because the Sun moves about 1° per year in secondary progression, the solar arc also accumulates roughly 1° per year. This steady, almost linear speed makes arc directions well suited to precise timing: an orb of about 1° corresponds to roughly a one-year event window. This tool can also produce the arc from the Ascendant or Vertex instead of the Sun; in addition it offers the Naibod arc, based on a constant mean solar motion.
"The distance the Sun covers in a day corresponds to one year of life." When this measure is converted into a single equal arc for the whole chart, the solar arc direction is obtained; the technique was systematised widely in the 20th century.
The classical "one day, one year" measure
The Source of the Arc: Four Methods
1. Solar Arc (Sun arc, default). The arc is the angle the progressed Sun has travelled from the natal Sun. It accumulates roughly 1° per year and is almost linear; this is the most classical and most widely used form.
2. Ascendant arc. The arc is the angle the progressed Ascendant has travelled from the natal Ascendant. Because the Ascendant depends on latitude and the obliquity of the celestial sphere, this arc is not linear; its speed can vary within the year. It depends directly on the birth time.
3. Vertex arc. The arc is the angle the progressed Vertex has travelled from the natal Vertex. Since the Vertex is also an oblique spherical function, this arc too is not linear. Like the Ascendant arc, it is sensitive to the birth time.
4. Naibod arc. The arc is given by the Sun's mean daily motion per year of age (0.9856°). It is a smooth, predictable constant arc that removes the seasonal fluctuation in the real solar speed.
Whichever method is chosen, the resulting arc is added in the same amount to all without exception natal points and angles. For the angles, the RAMC is advanced by this arc and the houses are recomputed.
How Is the Timing Read?
When the arc is applied and a directed point (for example the directed Sun, Mars or MC) forms an exact aspect to a natal point, the time that theme matures is read. Because the arc advances about 1° per year, a tight 1° orb places the event within roughly a one-year window. This is why hard aspects (conjunction, square, opposition) and a tight orb take priority in interpretation; a wide orb loses its meaning in arc directions.
The arc direction alone does not trigger the outer event; it is a symbolic clock. In classical practice the arc direction shows the maturing inner theme, while the transit shows the outer event that makes it visible. Read together, the timing becomes clear. This tool lays the ground for that reading by listing the aspects the directed points make to the natal points with an orb of ≤1°.
This tool is for educational and preparatory study; it does not replace a classical interpretation. Arc directions are a symbolic timing; the sky does not actually move at this speed. The Ascendant and Vertex arcs and the aspects to the angles depend directly on the birth time; if the time is uncertain, only the arc aspects between planets are reliable. For precise angle arcs, an accurate, ideally
rectified birth time is required.
Honest use note