Astrological Aspects: How the Planets in Your Birth Chart Talk

Astrological aspects are the angles between planets in a birth chart, measured in degrees along the zodiac. When two planets sit at certain angles, 0°, 60°, 90°, 120° or 180° apart, astrologers say they are in aspect: the two parts of you they represent work together, push against each other or keep each other company.

Signs and houses tell you what each planet is like and where it lives. Aspects tell you which planets are in conversation. Your Moon might be in a calm sign, but if it sits in a close square to Mars, your feelings arrive fast and hot. That is why two people with the same Sun, Moon and rising sign can feel so different: the conversations between their planets are different.

The five major aspects

The five major aspects are called the Ptolemaic aspects, after the 2nd-century astronomer Ptolemy, who set them out. Each one links signs in a particular way.

• Conjunction (0°): two planets in the same place, usually the same sign. Their functions fuse, so you cannot have one without the other. A Sun–Mercury conjunction makes thinking part of who you are.
• Sextile (60°): planets two signs apart, in compatible elements (fire with air, earth with water). It brings opportunity and easy cooperation, which works best when you use it.
• Square (90°): planets three signs apart, in the same mode but clashing elements. It brings friction, pressure and the need to act. Squares are where a lot of drive and achievement come from.
• Trine (120°): planets four signs apart, in the same element. It brings flow and natural talent, things you do without trying, and sometimes take for granted.
• Opposition (180°): planets in opposite signs, facing each other across the chart. It brings awareness through contrast, often lived out through other people, and asks for balance rather than a winner.

Minor aspects

Modern astrologers also use smaller angles. The best known:

• Quincunx or inconjunct (150°): two signs with nothing in common by element or mode. It brings a sense of constant adjustment, two needs that never quite fit.
• Semi-sextile (30°): neighbouring signs. A mild link between very different styles.
• Semi-square (45°) and sesquiquadrate (135°): smaller relatives of the square, with low-level friction.
• Quintile (72°) and biquintile (144°): linked by many astrologers to talent and style.

The 45°, 135°, 72° and 144° aspects were introduced by the astronomer Johannes Kepler in the 17th century, and most astrologers treat them as quieter than the major five. In Hellenistic astrology, signs 30° or 150° apart did not "see" each other at all; they were in aversion, with no aspect between them.

Orbs: how close is close enough

Planets are rarely exactly 90° or 120° apart, so astrologers allow an orb: a margin either side of exact. Here the traditions differ, and the difference explains why charts disagree.

• Modern practice gives each aspect its own orb, widest for conjunctions and oppositions (often 8° to 10°) and narrower for sextiles. There is no fixed standard; every author and program sets its own.
• Medieval and Renaissance practice gave orbs to planets, not aspects. William Lilly, writing in 1647, gave the Sun about 15°, the Moon 12°, Jupiter and Saturn 9°, and Mars, Venus and Mercury 7°. Two planets were in aspect within half the sum of their orbs: Sun and Mercury within (15 + 7) ÷ 2 = 11°.
• Hellenistic practice counted aspects by sign: any planet in Aries squares any planet in Cancer. A closer contact, within about 3°, counted as stronger.

The tighter an aspect, the louder it speaks. An aspect within 1° or 2° shapes the whole chart; one at the edge of its orb is a quieter thread. If a chart's header reads "Placidus Orb: 0", that orb is most likely a house-cusp setting rather than an aspect orb; Placidus and Orb 0 on a birth chart explains the difference.

Applying and separating aspects

An aspect is applying when the faster planet is still moving toward the exact angle, and separating when it has passed it. Traditional astrologers give applying aspects more weight, because they describe something coming into being.

A worked example: the Moon at 10° Aries and Saturn at 14° Cancer are in a square, 4° from exact. The Moon moves faster and needs to reach 14° Aries to complete it, so the square is applying: a theme of emotional pressure and responsibility that is building. Move the Moon to 18° Aries and the same square is separating, a theme already lived through and absorbed.

Retrograde motion can reverse this, so check which planet is moving which way.

Out-of-sign aspects

Sometimes two planets are within orb of an aspect by degree but in signs that do not normally make it. Mercury at 29° Scorpio and Mars at 2° Pisces are 93° apart, a square by degree, yet Scorpio and Pisces are both water signs, which normally make a trine.

Astrologers disagree about these "dissociate" aspects. Some ignore them, some count them with a tighter orb, and some treat them as fully valid; in whole-sign Hellenistic practice, the sign relationship wins, so this pair would read as a trine. Read them as you would any mixed message: square-like tension, softened by an underlying ease.

Are hard aspects bad?

No. Squares and oppositions are called hard aspects because they bring friction, and friction is how a lot of growth happens: many people's greatest strengths sit right on their hardest aspects. Trines and sextiles are soft, bringing ease, which can turn into coasting.

Traditional astrology adds a sharper point: the planets matter more than the angle. A trine from a struggling Saturn can still bring weight, and a square from a well-placed Jupiter can still bring good fortune. Read the planets first, the angle second.

Aspect patterns

When several aspects link three or more planets, they form a pattern that shapes the whole chart:

• T-square: two planets in opposition, both square a third. All the tension runs through that third planet, the apex, which becomes the chart's engine.
• Grand trine: three planets in trine, usually in one element. A closed circle of talent and ease, at its best when something else in the chart gives it a push.
• Grand cross: four planets in two oppositions linked by four squares. Strong, driven and pulled in four directions at once.
• Yod: two planets in sextile, both quincunx a third. A modern pattern, read as a sense of mission or a skill that keeps demanding adjustment.
• Stellium: three or more planets in one sign or house, a concentration rather than an angle. Stellium meaning covers it.

How to start reading your aspects

1. Find the tightest aspects first, those within 1° to 3°. They are the loudest voices.
2. Look at aspects to your Sun, Moon, rising sign and chart ruler. They colour everything.
3. Read each one as a conversation: what does each planet want, and how does the angle make them meet?
4. Note whether it is applying or separating.
5. Then step back and look for patterns, such as a T-square or a grand trine.

The planet, sign and house formula tells you who each planet is; aspects tell you who it talks to. How to read your birth chart puts both into one step-by-step method, and your birth chart on Celestio comes with a reading written for that chart, its aspects included.

Frequently asked questions

What are aspects in astrology?

Aspects in astrology are specific angles between two planets or points in a birth chart, measured along the zodiac. The five major aspects are the conjunction (0°), sextile (60°), square (90°), trine (120°) and opposition (180°). Each describes how the two planets' functions interact: fusing, cooperating, clashing, flowing or balancing. Aspects show which parts of a chart are in conversation.

What orb should I use for aspects?

No single orb for aspects is standard. Modern astrologers commonly allow 8° to 10° for conjunctions and oppositions, around 6° to 8° for squares and trines, and 4° to 6° for sextiles, with a little more when the Sun or Moon is involved. Tighter is stronger: an aspect within 1° or 2° matters most. Different orb settings are why sites list different aspects.

Is a square in my birth chart bad?

A square in a birth chart is not bad. A square links two planets that want different things, so it creates friction and the push to act. Many people's strongest drives and best-earned skills sit on a square. Traditional astrologers add that the planets involved matter more than the angle: a square from a well-placed Jupiter can still bring good things.

What is an out-of-sign aspect?

An out-of-sign aspect is an aspect within orb by degree whose planets sit in signs that do not normally make that aspect. Mercury at 29° Scorpio and Mars at 2° Pisces are 93° apart, a square by degree, though their signs make a trine. Astrologers disagree on them: some ignore them, some count them more weakly and some treat them as fully valid.

What is the difference between an applying and a separating aspect?

An applying aspect is one where the faster planet is still moving toward the exact angle; a separating aspect is one where it has already passed it. Traditional astrologers give applying aspects more weight, because they describe something building rather than fading. The Moon at 10° Aries squaring Saturn at 14° Cancer is applying; at 18° Aries it would be separating.