Parallels and contraparallels of declination
Standard in English astrology by the 1780s; the trail before that runs cold
Ptolemy sorts signs that sit equidistant from the same tropic and notes that they “are on equal parallels” — but he never builds an aspect between two bodies out of it. His aspects are divisions of ecliptic longitude and nothing else. The idea descends instead as antiscia, the mirroring of a degree across the solstitial axis, whose whole point is that mirrored degrees share a declination. Somewhere between the two the mirror was re-read as a contact between planets, and by the time Ebenezer Sibly writes in the 1780s it is ordinary: he calls zodiacal parallels “what are commonly called Antiscians” — commonly called, meaning he is reporting a usage already current, not coining one.
What it measures
Declination is a body's angular distance north or south of the celestial equator — the coordinate the stars are catalogued in, not the zodiacal one. Two bodies are parallel when their declinations are equal on the same side, contraparallel when equal in size on opposite sides. It ignores longitude completely, so two planets a third of the sky apart can be exactly parallel: on the ecliptic, 0° Taurus and 0° Virgo are 120° apart and both sit near 11.5° north.
Where practitioners disagree
- Is a contraparallel read like an opposition?
Contraparallel ≈ opposition (the modern default) — or no split at all, with north and south treated as irrelevant
The two-member pair is old: Sibly already distinguishes a planet's antiscion from its contra-antiscion. What is missing in the early sources is any difference in meaning between them. Zadkiel is blunt in 1833 — in a parallel, “whether of the same name, north or south, is of no consequence.” The pair predates the split; who introduced the split is not attested.
This engine: Contraparallel is labelled and read as the opposition-like contact — the modern convention. - True declination, or declination derived from longitude alone?
The body's real declination, latitude included — or the longitude-only shortcut, which is really the antiscion
They agree only for a body sitting exactly on the ecliptic. Sibly quantified the gap in the 1780s: the Moon at 22° Taurus with 5° north latitude lands 28° of longitude away from where the naive method puts her. The divergence is severe for the Moon (latitude to about 5.3°) and extreme for Pluto (about 17°).
This engine: True apparent declination from the ephemeris, latitude included. The antiscion is computed separately, on the Midpoints tab, and never conflated with this. - What orb?
1°00′ is the common modern default; some use 0°30′ or tighter; some scale it by body
No orb appears in the early sources at all — Sibly, Raphael and Zadkiel speak only of exact or close parallels. The orb is a later addition.
This engine: 1° of declination, stated on the panel.
Still open
Raphael (1828) and Zadkiel (1833) are the two names usually credited, and both are heirs rather than sources. Zadkiel gives himself away in his own sentence — “The Zodiacal Parallel. — This was formerly termed the anti-scion” — and his complaint that the old writers omitted the planet's latitude repeats Sibly's objection from a generation before. Where the technique actually began could not be established.
Sources
- Claudius Ptolemy, Tetrabiblos I.13–15 (2nd c. CE)
- Ebenezer Sibly, A New and Complete Illustration of the Celestial Science of Astrology (1784)
- John Worsdale, Genethliacal Astrology (1798)
- Raphael (Robert Cross Smith), A Manual of Astrology (1828)
- Zadkiel (Richard James Morrison), The Grammar of Astrology (1833)