Astrological Aspects: Conjunction, Opposition, Trine, Square

What is an aspect?

When you look at the sky at birth, each heavenly body occupies a position along the zodiac, expressed in degrees (from 0 to 360, or from 0 to 29 within a sign). An aspect is the angle separating two heavenly bodies, or a heavenly body and a point such as the ascendant. Astrologers mainly use the angles obtained by dividing the 360-degree circle into simple parts: by 2 (180°), by 3 (120°), by 4 (90°), by 6 (60°). This fondness for simple divisions comes from ancient Greece, notably from the Pythagorean school; even earlier, Chaldean astronomers had already observed conjunctions and oppositions.

The five major aspects

These five aspects are the ones described by Ptolemy in the Tetrabiblos (2nd century). He classed the trine and the sextile as favorable, the square and the opposition as unfavorable, and the conjunction as capable of going either way. In the tradition, a trine or a sextile is “flowing”, a square or an opposition “tense”.

Orb: how many degrees of difference?

Two heavenly bodies are never exactly 120 or 90 degrees apart. The orb is the margin of difference accepted before we say there is an aspect. It varies widely between authors. As an example, here are typical values given in French reference books: conjunction up to 10°, opposition 10°, trine 8°, square 6°, sextile 4°. Other sources give tighter orbs (5 to 8 degrees) or wider ones for the Sun and the Moon. The smaller the orb, the “tighter” the aspect is said to be, and therefore the stronger.

Two further notions: an aspect is called applying when the faster body is moving toward the exact angle, and separating when it is moving away from it. Traditionally, the applying aspect is considered more active.

Step-by-step calculation, with two examples

1. Note the position of each heavenly body in degrees along the zodiac, from 0° (start of Aries) to 360°. Each sign is worth 30°: Aries from 0 to 30, Taurus from 30 to 60, Gemini from 60 to 90, and so on up to Pisces from 330 to 360.
2. Subtract one position from the other.
3. If the result exceeds 180°, subtract it from 360° to get the shorter angle.
4. Compare with the angles of the aspects and check whether the difference falls within the orb.

Example 1. The Sun is at 15° Aries (position 15°) and the Moon at 17° Libra (Libra begins at 180°, so the position is 197°). Difference: 197 − 15 = 182°. This is a gap of 2° from the opposition (180°): the aspect exists, with an orb of 2°.

Example 2. Mars is at 10° Gemini (60 + 10 = 70°) and Saturn at 5° Aquarius (Aquarius begins at 300°, so the position is 305°). Difference: 305 − 70 = 235°, which exceeds 180°; the shorter angle is 360 − 235 = 125°. A gap of 5° from the trine (120°): there is an aspect if the accepted orb is 5° or more.

Minor aspects

Some astrologers use other angles, called minor: the semi-sextile (30°), the semi-square (45°), the quintile (72°, one fifth of the circle), the sesquiquadrate (135°), the biquintile (144°) and the quincunx (150°). Johannes Kepler, in Harmonices Mundi (1619), described thirteen of them, based on harmonic ratios inspired by music. Their orbs are tighter (generally 1 to 3 degrees), and their use varies from one school to another. For beginners, the five major aspects are enough.

Aspects between signs and aspect patterns

In ancient astrology, two heavenly bodies could be considered in aspect because their signs were (two signs three apart are in square, four apart in trine, and so on), even if the exact distance in degrees exceeded the modern orb. This way of counting is one of the differences between traditional and modern astrology (see the modalities: signs in square or in opposition share the same modality).

When several aspects combine, astrologers speak of patterns: the grand trine (three bodies 120° apart from one another, within the same element), the T-square (two bodies in opposition, each forming a square with a third), the grand cross (four bodies in squares and oppositions), the stellium (at least three bodies gathered in the same sign). These patterns are handy visual landmarks when reading the chart drawing.

What aspects are worth

Aspects are the “links” of a chart: the reading is built from them. But they pose a statistical problem. With ten heavenly bodies, there are 45 possible pairs. With the orbs listed above (10° for the conjunction and the opposition, 8° for the trine, 6° for the square, 4° for the sextile), roughly 31% of pairs fall into an aspect by pure chance, so about fifteen aspects in any random chart (simple calculation: fifty-six degrees of accepted gap out of a possible one hundred and eighty between two bodies). Every chart therefore contains many aspects, and one can almost always find an explanation for any trait. This is what makes readings convincing… and hard to refute.

Aspects are thus a language of symbols. For beginners, a good habit is to limit yourself to the tightest aspects (a gap of 2 or 3 degrees) involving the Sun, the Moon or the ascendant. See the history and limits of astrology.

Frequently asked questions

Also read

The meanings mentioned belong to tradition and symbolism. They are neither promises of results nor medical advice. Back to Guide to astrology basics.