How Stars & Saju Works

Stars & Saju exists for one reason: two traditions read the same birth moment, they usually disagree, and almost nobody puts them side by side.

The calculations

Planets

Positions come from NASA JPL DE440 ephemeris data — the same lineage used for spacecraft navigation. We compute apparent geocentric ecliptic longitude: where each body genuinely appeared from Earth at your birth moment, with light-time and aberration accounted for.

Houses

Placidus by default, computed by iterating each cusp against the declination of the point rather than approximating with even angles. Above the polar circles Placidus is mathematically undefined; there we fall back to whole sign houses, and your chart says which system was used.

Saju pillars

Your Saju year turns at ipchun, which we solve for by finding the instant the Sun reaches 315 degrees of ecliptic longitude — not by looking up a fixed February date. Month pillars turn at the twelve major solar terms, found the same way. Day pillars follow the continuous sexagenary cycle, verified against reference calendars. Hour pillars use time corrected to your birth meridian, because clocks are political and hour branches are solar.

The interpretation

Reports are composed from your complete chart in one pass rather than assembled from a template library, which is why they can hold a contradiction instead of flattening it. Every section names the placements it reads from, so nothing has to be taken on trust — you can check any claim against the free calculators on this site.

Each finished section is also checked back against the computed chart to catch the one failure that would genuinely embarrass us: confidently describing a placement you do not have.