Derived Charts

Derived charts start from a natal chart and apply a transformation to create a new chart that reveals different layers of meaning. The Morphemeris API supports two types: secondary progressions and draconic charts.

Secondary progressions

The idea: One day of planetary motion after birth equals one year of life.

Secondary progressions are the most widely used predictive technique in Western astrology. They work by mapping the slow unfolding of the first months after birth onto the decades of a life. The planetary positions 30 days after birth become the progressed chart for age 30.

What moves

• Progressed Sun — Moves about 1° per year (one sign every 30 years). A progressed Sun changing signs is a major life shift.
• Progressed Moon — The fastest body, moving about 12° per year (one sign every ~2.5 years). The progressed lunar cycle is one of the most reliable timing tools in astrology.
• Progressed inner planets (Mercury, Venus, Mars) — Move slowly but can change signs, station retrograde/direct, or form aspects to natal planets.
• Progressed outer planets — Move so slowly they barely change from their natal positions. Outer planet progressions are generally not interpreted.

Station events

When a progressed planet stations (changes direction between retrograde and direct), it marks a significant turning point in the area of life that planet represents. These are among the most powerful progressions.

How the API handles it

The /v1/progressed endpoint takes a natal datetime and a target datetime, computes the progressed datetime using the day-for-a-year ratio, and returns a full chart (positions, houses, aspects, dignities) for the progressed moment.

API endpoint: /v1/progressed (2 credits)

Draconic chart

The idea: Measure everything from the North Node instead of the vernal equinox.

The tropical zodiac measures positions from 0° Aries — the point where the Sun crosses the celestial equator at the March equinox. The draconic chart redefines 0° Aries as the North Node (where the Moon's orbit crosses the ecliptic heading north), then measures all positions relative to that point.

How it works

1. Find the North Node's ecliptic longitude (e.g., 132.5°)
2. Subtract that longitude from every position in the chart
3. The North Node is now at 0° Aries; everything else shifts accordingly

This is a pure rotation — aspects between bodies are preserved because all positions shift by the same amount. Only the sign placements change.

Mean node vs. true node

The Moon's orbit wobbles (a phenomenon called nutation), which means the North Node oscillates by about ±1.5° around its mean position over an 18.6-year cycle:

• Mean node (default) — The averaged, smoothly moving position. Most astrologers use this for draconic charts.
• True node — The instantaneous position including the oscillation. Produces slightly different draconic positions.

Use the node parameter to choose.

Interpretation

The draconic chart is often called the "soul's chart" in spiritual and evolutionary astrology. It's interpreted as a layer beneath the tropical chart — the deeper patterns and purposes that the tropical personality expresses. Comparing draconic positions to tropical positions (either within one chart or between two people's charts) is a common technique.

API endpoint: /v1/draconic (2 credits)

Planetary returns

Planetary returns — when a transiting body returns to its natal longitude — are another form of derived chart. See Planetary Returns for details.