Antiscia Backend Standard

Subsystem: moira/antiscia.py Computational Domain: Solstitial and equinoctial longitude reflections Status: Backend standard for Phase 12 REST admission

---

1. Scope

This standard governs Moira's ordinary antiscia backend surface:

• AntisciaAspect
• antiscion(longitude)
• contra_antiscion(longitude)
• find_antiscia(positions, orb=1.0)
• antiscia_to_point(point_longitude, positions, point_name="Point", orb=1.0)

The subsystem computes zodiacal mirror points and contact searches over ordinary ecliptic longitudes. It is a pure arithmetic astrology engine. It does not compute planetary positions, house cusps, primary directions, or chart motion.

2. Authority And Provenance

The implemented canon named by the module is:

• Vettius Valens, Anthology II.37
• William Lilly, Christian Astrology (1647), p. 90

The computational authority in Moira is the explicit reflection formula:

antiscion(longitude)        = (180 - longitude) mod 360
contra_antiscion(longitude) = (360 - longitude) mod 360

These formulae are the backend doctrine. Transport layers may expose them but must not replace them with sign-name lookup tables or interpretive shortcuts.

3. Governing Objects

3.1 Antiscion point

An antiscion point is the reflection of a zodiacal longitude across the 0 Cancer / 0 Capricorn solstice axis.

3.2 Contra-antiscion point

A contra-antiscion point is the reflection of a zodiacal longitude across the 0 Aries / 0 Libra equinox axis.

3.3 Antiscia contact

An AntisciaAspect records one admitted contact:

• body1
• body2
• aspect as "Antiscion" or "Contra-Antiscion"
• lon1
• lon2
• reflected shadow
• angular orb

The shadow field is the reflected longitude of body1. The orb is the minimum circular angular distance between shadow and lon2.

4. Admitted Computations

4.1 Direct reflection

The direct primitive returns a reflected longitude in [0, 360).

Admitted forms:

• antiscion of one longitude
• contra-antiscion of one longitude
• both reflections of one longitude

4.2 Pair contact search

find_antiscia(positions, orb) tests unordered body pairs for both antiscion and contra-antiscion contact. For each pair and aspect kind, it checks both directions and keeps the tighter direction when either direction qualifies. Results are sorted by increasing orb.

4.3 Point contact search

antiscia_to_point(point_longitude, positions, point_name, orb) tests whether each supplied body casts an antiscion or contra-antiscion onto one fixed target point. Results are sorted by increasing orb.

5. Required Transport Invariants

Any REST admission for /v1/antiscia/* must preserve these invariants:

• reject non-finite longitudes before calling the engine
• normalize or document longitude wrap policy explicitly
• reject negative, non-finite, or unreasonably large orb values
• require unique non-empty body names in position maps
• preserve the engine labels "Antiscion" and "Contra-Antiscion"
• preserve body1 as the body whose reflected point forms the contact
• preserve shadow and orb explicitly in responses
• sort contact responses by increasing orb
• bound chart/contact request size before public exposure

Transport should admit direct reflection routes before chart-wide contact routes.

6. Primary-Direction Boundary

Ordinary antiscia and primary-direction antiscia are distinct surfaces.

This standard governs moira.antiscia only. It does not govern:

• moira.primary_directions.antiscia.PrimaryDirectionAntisciaKind
• PrimaryDirectionAntisciaTarget
• project_primary_direction_antiscia_longitude
• primary-direction arc search using antiscion targets

The primary-direction subsystem may use the same reflection formula for target projection, as verified by tests/unit/test_primary_direction_antiscia.py, but its governing object is a primary-direction target and arc, not an ordinary chart antiscia contact.

REST documentation must not merge /v1/antiscia/* with primary-direction routes or imply that ordinary antiscia contact search computes directed arcs.

7. Validation Requirements

Minimum validation for transport admission:

.\.venv\Scripts\python.exe -m py_compile moira\antiscia.py
.\.venv\Scripts\python.exe -m pytest tests\unit\test_astrology_adversarial_gauntlet.py tests\unit\test_primary_direction_antiscia.py -q

The transport test suite must additionally cover:

• antiscion is an involution
• contra-antiscion is an involution
• boundary values at 0, 90, 180, 270, and wrap-adjacent longitudes
• pair-search deduplication
• point-search output ordering
• non-finite longitude rejection
• invalid orb rejection

8. Non-Goals

This subsystem does not provide:

• ephemeris computation
• house calculation
• aspect search beyond antiscion and contra-antiscion contacts
• primary-direction arc search
• directed symbolic interpretation
• antiscia networks or scoring profiles
• transit, progression, or solar-return orchestration

Those products require separate route design or separate subsystem standards.

9. Change Policy

The following are doctrine-sensitive and require explicit review before change:

• the two reflection formulae
• the meaning of Antiscion and Contra-Antiscion
• deduplication semantics in pair searches
• result ordering by orb
• the boundary between ordinary antiscia and primary-direction antiscia

The REST layer may validate, serialize, and bound the current backend. It must not introduce hidden interpretive scoring.