History & development
Secondary progressions, solar arcs and primary directions are different timing constructions. Secondary progression uses a symbolic day-for-year correspondence. Solar-arc methods shift factors by a selected solar motion. Primary directions concern diurnal geometry. Software documentation shows that even a 'progressed' chart can combine secondary planets with differently advanced angles.
Mythology & symbolic world
The central analogy is that a short celestial interval can represent a longer life interval. This is a symbolic correspondence, not a claim that planets physically moved to the displayed positions at the person's present age.
Provenance: where the rules come from
Record the target age, year length, direct or converse convention and treatment of angles. For primary directions, additional geometric definitions and a time key must be specified before results are comparable.
How it is calculated
Choices that change the result: Rate, year length, converse/direct motion and house treatment must be named.
Inspect your calculated data →Uses & use cases
- Understand why a progressed chart differs from today's transit chart.
- Audit apparent disagreements between two software packages.
Interpretation methods
Method-separated timeline
Display the symbolic date or arc alongside the target life date, then trace each listed contact back to the named construction.
At exactly 30 symbolic years, a day-for-year method samples 30 days after birth. It does not sample the sky 30 calendar years later.
Explore these reading approaches
Concepts in this tradition
Follow a term for its definition, word origin, evidence and connected ideas.
Disagreements & limits
- A uniform one-degree-per-year rotation is not identical to every solar-arc method.
- Primary directions are not implemented by adding an arbitrary longitude offset.
Sources & evidence
Practitioner sources describe their own systems. Historical and astronomical sources support different kinds of claims. Reading exercises are editorial teaching examples.
- Astrodienst: chart types and progression conventions ↗first-party chart-method documentation
- Astrodienst: progressed angle alternatives ↗first-party chart-method documentation