Chart Construction Methodology (七政四餘排盤法)
Constructing a QZSY natal chart requires both calendrical calculation (shared with BaZi) and astronomical computation (unique to QZSY). The process transforms a birth date, time, and location into a complete celestial map showing the positions of all eleven bodies within the twelve houses. This module outlines the systematic step-by-step methodology.
Step-by-Step Construction Process
- Step 1 — Convert Birth Data to GanZhi Pillars: Using the Chinese sexagenary calendar, derive the four pillars (Year, Month, Day, Hour) of Heavenly Stems and Earthly Branches. This step is identical to BaZi chart construction and provides the temporal foundation.
- Step 2 — Determine the Ascendant (命宮): Calculate which Ci (十二次 division) is rising on the eastern horizon at the exact birth time and geographic location. This requires knowledge of local sidereal time, geographic latitude, and the obliquity of the ecliptic. The Ascendant anchors the entire house system.
- Step 3 — Lay Out the Twelve Houses: Starting from the Ascendant's Ci position, assign the twelve houses in sequence around the chart frame. Each house occupies one Ci (30 degrees).
- Step 4 — Compute Planetary Longitudes: Using an ephemeris (historically, hand-computed tables; modernly, the Swiss Ephemeris), determine the ecliptic longitude of each of the Seven Governors at the birth moment. This is the most computationally intensive step and the reason QZSY was historically far more difficult to practice than BaZi or ZWDS.
- Step 5 — Apply Sidereal Correction: Convert tropical (equinox-based) coordinates to sidereal (star-fixed) coordinates by subtracting the appropriate ayanamsa (歲差, precession correction). The choice of ayanamsa affects all planetary positions by roughly 23-24 degrees in the current era.
- Step 6 — Map Bodies into Mansions and Houses: Place each planet's sidereal position into its corresponding Lunar Mansion (for fine analysis) and Ci/House (for house-based interpretation). Record the exact degree within each mansion.
- Step 7 — Calculate Four Remainders: Compute the positions of Rahu (羅睺), Ketu (計都), Purple Gas (紫氣), and Moon's Apogee (月孛) using their respective orbital formulae. Place them on the chart alongside the Seven Governors.
The Ayanamsa Question
The ayanamsa (歲差) — the angular difference between the tropical and sidereal zodiacs due to the precession of equinoxes — is one of the most technically important decisions in QZSY practice. Different ayanamsa values shift all planetary positions by the same amount, potentially moving planets into different mansions and houses. Classical Chinese texts used various precession values; modern practitioners typically adopt the Lahiri ayanamsa (used in Indian Jyotish) or a specifically Chinese value derived from historical star catalogues. This choice can significantly affect chart interpretation.
Manual vs Software Methods
Historically, QZSY chart construction required mastery of complex astronomical tables and calculation procedures — a significant barrier to entry that contributed to QZSY's relative rarity compared to the simpler BaZi and ZWDS systems. Modern software using the Swiss Ephemeris can compute all planetary positions to sub-arcsecond precision in milliseconds, removing the computational barrier entirely. The platform's /api/calculators/qzsy endpoint leverages this capability to generate complete QZSY charts programmatically.
Quality Control
A well-constructed QZSY chart should be verified against known astronomical data. Key checks include: (1) the Moon's position should match observable lunar mansion for the birth date, (2) planetary positions should be consistent with historical ephemeris data, (3) the Ascendant should be plausible for the birth time and location. Errors in birth time have a particularly large impact on the Ascendant and house positions, making accurate birth records essential.