Contra-parallel Rules

Interpretation/Fixed Stars/Contra-parallels/rules.md

interpretation · fixedstars · contraparallels

Contra-parallel Rules

1. Use a one-degree orb.
2. Consider as a declinational opposition.

Backlink: Contra-parallel Overview.

📏 Rules — Expanded

3. Use declinations of date (precession changes stellar declination by up to ≈ 20″/yr).
4. Tight orb: ≤ 1° (some authors allow 1°10′); exactness within 0°20′ is strong.
5. Count only opposite-side (N/S) matches.
6. Note out-of-bounds bodies (|δ| > 23°26′): they can reach stars no in-bounds planet can.
7. Combine with longitude conjunctions: a star both conjunct and contra-parallel a body is doubly emphasised.
8. Read the contact through the star note’s High/Shadow Expression and the planet’s nature (book method: body × star).

Tables: declination table.

Sources (method)

• Jean Meeus, Astronomical Algorithms, 2nd ed. (Willmann-Bell, 1998) — ch. 13 (coordinate transforms), ch. 47 (Moon, nodes, perigee/apogee)
• Swiss Ephemeris fixed-star catalogue sefstars.txt (ICRS/Hipparcos-based positions, proper motions, magnitudes): https://github.com/aloistr/swisseph/blob/master/ephe/sefstars.txt — ecliptic longitudes computed for this vault with Astropy 8.0 (GeocentricMeanEcliptic, mean equinox of J2000.0 and of 2026-01-01)