Declination, Parallels and Contraparallels
Everything so far has been about the coordinate measured along the plane. This page is about the other one — the distance measured away from it — and about a relationship two bodies can have that ordinary aspects cannot see.
Aspects measure along; parallels measure across
An ordinary aspect is an angular separation along the reference circle. A trine is 120° of longitude between two bodies; a square is 90°. The second coordinate plays no part.
A parallel is the other axis entirely:
- A parallel is two bodies at the same distance from the plane, on the same side of it.
- A contraparallel is two bodies at the same distance from the plane, on opposite sides of it.
Two bodies can be parallel while sitting anywhere at all in longitude — 4° apart or 137° apart, it makes no difference. The relationship is about height above the plane, and it is invisible to any technique that only looks along the circle.
That is what makes it worth having. It is a genuinely independent measurement, not a restatement of an aspect in different words.
Which measurement gets matched
Here is where this page belongs to this category.
The applications match parallels in the frame's own away-coordinate — the second number, whichever plane you have selected:
| Ref. Plane | Parallels are matched in |
|---|---|
| Ecliptic | celestial latitude — distance from the ecliptic |
| Equatorial | declination — distance from the celestial equator |
These are not the same relationship computed two ways. As Projecting Between the Planes established, celestial latitude and declination are different numbers for the same body, measured from different circles towards different poles. Two bodies matched in one are not generally matched in the other.
The Sun makes the point once more. Its celestial latitude is zero all year, so in the ecliptic frame it is parallel to anything else sitting on the ecliptic and carries no information. Its declination swings across 47° in a year, so in the equatorial frame it forms parallels and contraparallels continuously as it moves. Same body, same year, two frames, and only one of them has anything to say.
Declination is the traditional one
When astrological literature refers to parallels and contraparallels without qualification, it almost always means declination — the equatorial measurement.
The technique is old and predates the availability of anything else: declination was what the tables gave, because equatorial coordinates are what observational astronomy produces. A contraparallel of declination is often treated as carrying something of the character of an opposition, and a parallel something of a conjunction, on the reasoning that bodies at matching declinations share the same daily path across the sky.
So if you want parallels in the traditional sense, you need the Equatorial plane. Selecting Ecliptic gives you parallels of celestial latitude, which is a coherent measurement and is not the one the literature is describing.
Where this appears in the applications
Compass exposes it directly on the chart settings panel: Paral. Aspects offers None, All, Parallels or Contraparallels, deciding which of the two are drawn on the wheel.
Turn them on together with the display of the away-coordinate itself. Parallels drawn without the numbers they were matched on are lines you cannot check.
Why the ecliptic frame cannot substitute
A reasonable question: if the two frames are related by a fixed 23.4° tilt, why not compute declination while working in the ecliptic frame?
The applications could, and the reason they do not is consistency. A frame is a matched pair of coordinates — along and away — and mixing the along-coordinate of one with the away-coordinate of the other produces a description that is not a position in any frame. Orbs, comparisons and stored results would all be running in a hybrid that has no clean definition.
Selecting the Equatorial plane is how you ask for declination, and it changes both coordinates together, which is what keeps the answer coherent.
What comes next
Everything the setting does is now on the table: what it changes about position, about timing, about vocabulary, and about which relationships are visible.
Next: Choosing a Reference Plane.