Opposition aspect: two bodies facing each other at 180°

Ptolemy opens his list of aspects with the opposition (Tetrabiblos, book I, chapter 13): two signs six signs apart, 180°, two right angles. His explanation is the briefest of all: it is “immediately obvious,” since the two signs meet on one straight line. The opposition then serves as the measure for the others: half of it gives the square, and its thirds the sextile and the trine.

Ptolemy ranks the opposition with the square among the disharmonious aspects, and the trine and the sextile among the harmonious ones. This division between aspects that agree and aspects that clash runs through the whole tradition from then on.

William Lilly takes up the distinction in Christian Astrology (1647, book I, chapter XIX), in the setting of horary astrology, the branch that answers a question put to the astrologer. He calls the opposition “diametral radiation” and makes it an argument of perfect hatred, whereas the square is only imperfect enmity. His example: can two adversaries be reconciled? If their significators are in square, there is still hope; if they are in opposition, no peace is to be expected until the lawsuit is ended or the duel fought.

This vocabulary judges the outcome of a matter, not a character. In modern natal astrology, the opposition is read instead as a polarity: two needs answering each other from either end of an axis.

Reading an opposition means identifying the two functions involved and watching how they pull in opposite directions while staying linked. One does not cancel the other. The energy tends to swing now to one pole, now to the other: back-and-forth, repeated trade-offs, and sometimes projection, when what we do not integrate in ourselves turns up in other people. The legend of the aspect table in your report sums it up in one word: tension.

With the Sun opposite the Moon, what you want to build and what your inner world demands face each other. The point is not to choose, but to learn to bring self-assertion and attention to your needs into dialogue. The houses of the two bodies tell you on what ground this back-and-forth plays out.

In your birth chart and in the Book, the orb of the opposition is 8°: two bodies 172° to 188° apart are in opposition. This tolerance is the same for all bodies, without the widening tradition granted the Sun and the Moon. What distinguishes a tight opposition from a wide one is the orb itself, written in degrees and minutes in the aspect grid, where the name of the aspect appears in red.

With Lilly, the tolerance would have varied with the pair of bodies. His rule of separation applies to all aspects: the Moon is fully separated from the Sun only at 13°30', half the Sun's orb (7°30') plus half her own (6°). A Sun-Moon opposition at 10° would therefore still count for him; for AstralPro, it drops out of the grid past 8°.

Other uses have their own, narrower thresholds. The wheel draws an opposition only at 5° or less. The internal aspects of the solar return and the compatibility table use 7°. The Book, to detect its major figures (T-square, grand cross), goes down to 6°. As with any aspect, the Direction column says whether the opposition is forming or coming apart, except when an angle is involved or both bodies are slow.

Camille Morel, AstralPro's sample chart (fictional data), has no opposition between two planets. The reason can be read in her positions table: her planets occupy Scorpio, Sagittarius, Capricorn and Aquarius, and the four opposite signs, from Taurus to Leo, are empty.

Her grid has a single opposition, on line 36 of 40: Saturn opposition Midheaven, orb 6°22'. Saturn is at 23°53' Aquarius, in the 3rd house, and the Midheaven at 0°15' Virgo. Several columns carry a dash. Direction, because the Midheaven turns with the Earth and has no planetary motion. Reading, because the aspect exceeds the 3° up to which that column comments. On the wheel, the opposition is not drawn: it exceeds the 5° threshold. And it is not among the twenty aspects discussed in chapter I.

An opposition to the Midheaven is also a conjunction to the Imum Coeli, at 0°15' Pisces. The grid connects only the Ascendant and the Midheaven, so this contact is written only once.

The same principle applies to the axis of the Nodes, whose two ends are always exactly opposite. The grid carries only the North Node: its last line, Pluto conjunction North Node (7°43'), also places Pluto opposite the South Node, which the Karmic Chart chapter places in Gemini, in the 7th house. This face-off has no line of its own: it is read through the conjunction.

This opposition could have drawn a figure. Saturn is square Pluto (orb 1°24') and Pluto square the Midheaven (orb 4°58'). With Saturn opposite the Midheaven, the three points would form a T-square, an opposition whose two ends are both square to the same third body.

The Book, which devotes a chapter to the major figures, only keeps an opposition at 6° or less when detecting them. At 6°22', Camille's exceeds that threshold by 22 minutes of arc: the figure is not flagged. Her two squares do remain in the natal grid, and the Saturn-Pluto square is one of the aspects discussed, in the Love life section.

That is the value of reading the orb: an opposition at 6°22' does not weigh like an opposition at 0°30'. It is counted and displayed, but it stays at the bottom of the grid.