Shukuyō (27 Lunar Mansions) (宿曜道)

宿曜道 — The Moon's Mansion at Your Birth, and the Secret of the Bond

Overview

Shukuyō (宿曜道, 'the way of the mansions and luminaries') is the esoteric-Buddhist astrology that the monk Kūkai brought back from Tang China in the ninth century. Its centre is a single, elegant idea: the Moon, which crosses the whole sky in about 27 days, lodges each night in one of 27 lunar mansions (宿, shuku) — and the mansion it occupied at the hour of your birth is your 本命宿 (honmyō-shuku), the mansion of your fundamental destiny. From it Shukuyō reads temperament and fortune; and through its famous compatibility method, the 三九の秘法, it reads the hidden order of a relationship between any two people.

Origin & history

Shukuyō rests on the Sukuyō-kyō (宿曜経), the Chinese translation of an Indian astrological sutra brought to Japan by Kūkai (Kōbō Daishi) in 806 CE. Its 27 mansions are the Indian nakṣatra — the Moon's nightly stations along the ecliptic — the same lunar-mansion idea that underlies the Arabic manāzil and the Chinese 二十八宿, here carried through Buddhism into Japan. In the Heian court Shukuyō masters (宿曜師) were consulted for auspicious days and personal fortune, and the system left a deep mark on Japanese calendrical and folk practice. It survives today as one of Japan's popular character-and-compatibility astrologies.

There are two ways to find a birth mansion, and they matter. The older Japanese almanac method reads the mansion off a fixed lunar-calendar table — simple, but astronomically approximate, and known to skip or repeat mansions at month boundaries. The method used here is the true-Moon method: the mansion is the nakṣatra the Moon actually occupied at birth, computed from the ephemeris on the sidereal (Lahiri) frame — identical to the Vedic janma-nakṣatra, just renamed to its 宿. The two methods usually agree but can differ by one mansion near a boundary; this engine uses the astronomically exact reading and flags lower confidence when the Moon is within about a degree of a boundary. The mansion list is anchored by an astronomical certainty — 昴宿 (Bō) is the Pleiades, i.e. the nakṣatra Kṛttikā — which fixes the whole 27-mansion alignment.

How it works

Give a birth date (and, ideally, time and UTC offset). The engine computes the Moon's longitude on the shared Meeus ephemeris, subtracts the Lahiri ayanamsa to get the sidereal position, and divides by 13°20′ to find the mansion — your 本命宿. It returns the mansion's 宿 character and reading, its corresponding nakṣatra, its 七科分宿 nature (one of seven temperamental classes: 安住 settled, 和善 gentle, 急速 swift, 軽燥 restless, 悪害 sharp, 猛悪 fierce, 剛柔 firm-yet-soft), its 七曜 planetary and weekday ruler, and a character sketch — with a confidence flag when a missing time or a boundary makes the mansion time-sensitive. Supply a second person and it computes the 三九の秘法: the distance between the two mansions on the 27-ring gives the relationship — 命 (resonance), 業/胎 (the karmic past-life/future-life pair), or one of the eight-cycle bonds 栄 (prosperity) 衰 (decline) 安 (peace) 危 (danger) 成 (achievement) 壊 (destruction) 友 (support) 親 (affection) — read directionally, since each person sees the other through a classical mirror-paired lens.

Good for

Use cases

Your Birth Mansion

Send a birth date (and time) and get your 本命宿 — its character, its seven-class nature, and the planet and weekday that rule it.

The Secret of the Bond

Add a partner and the 三九の秘法 names the relationship on the 27-ring — resonance, a karmic pair, or one of the eight bonds from prosperity to destruction.

Directional Reading

The bond is asymmetric: you may bestow prosperity (栄) while they feel warmth (親). The engine reports both directions, the classical mirror pairs.

Honest Boundaries

The Moon crosses a mansion about once a day, so a missing or borderline birth time lowers the confidence — surfaced, never hidden.

Key terms

本命宿 (Honmyō-shuku)
Your birth mansion — the lunar mansion the Moon occupied at the moment of your birth, the seat of your fundamental character and destiny in Shukuyō.
宿 (Shuku)
A lunar mansion — one of the 27 equal 13°20′ segments of the ecliptic the Moon passes through, each a station lasting roughly a day.
三九の秘法 (Sankyū no hihō)
The 'secret method of three-nine' — Shukuyō's compatibility system, reading the relationship between two mansions by their distance on the 27-ring.
命業胎 (Mei-Gō-Tai)
The three karmic anchors of the compatibility ring, at distances 0/9/18: 命 resonance, 業 the past-life giver, 胎 the future-life receiver.
七科分宿 (Shichika-bunshuku)
The seven temperamental classes the 27 mansions fall into: 安住 settled, 和善 gentle, 急速 swift, 軽燥 restless, 悪害 sharp, 猛悪 fierce, 剛柔 firm-yet-soft.

API

The askTIAN Shukuyō endpoint finds your 本命宿 from a birth date and returns the mansion's character on the true sidereal-Moon method — the mansion is the Moon's nakṣatra (Lahiri frame) renamed to its 宿, equivalent to the Vedic janma-nakṣatra and gold-locked against Vedic anchors (Einstein → 心宿, Michael Jackson → 室宿). Each mansion carries its 宿 character and reading, its 七科分宿 nature, its 七曜 planetary/weekday ruler, and a character sketch, with a confidence flag when a missing or borderline birth time makes the mansion time-sensitive. Supply an optional partner and it computes the 三九の秘法 compatibility — the directional relationship between the two mansions on the 27-ring (命/業/胎 and the 栄衰安危成壊友親 cycle), each person seen through the classical mirror-paired lens, with auspicious/cautionary/karmic valence. A best-effort LLM reading is returned in parsable sections (set interpretation:false for structured data only). Honest rails: the true-Moon mansion is exact but the traditional Japanese almanac method can differ by ±1 mansion; a symbolic esoteric-Buddhist tradition for reflection, not a validated predictor — no medical, financial or legal advice, and no lifespan.

Endpoint: POST /trpc/shukuyo.calculate — 3 TIAN Points. See the API documentation and Playground.