Synastry: How Western Astrology Reads Chemistry Between Two People

Synastry is the Western astrological method for checking a couple that takes two natal charts and overlays them. Instead of reading each chart separately, the astrologer looks at: which planet of one person sits at what degree in the other's chart, and what angles form between them.

These angles are called aspects. Five main ones:

• Conjunction (0°) — merging. Very strong, intense.
• Opposition (180°) — mirroring. Tension and mutual complementarity.
• Square (90°) — challenge. Constant friction that forces growth.
• Trine (120°) — harmony. Easy flow, mutual support.
• Sextile (60°) — opportunity. Gentle support activated through effort.

So synastry isn't "72%." It's a map of specific interactions: where between you is tension, where lightness, where attraction, where friction.

Sun × Moon: the strongest indicator of long-term compatibility. When your Sun touches the partner's Moon (any aspect, especially harmonious), you feel a sense of "home." Your outer world (Sun) resonates with their emotional world (Moon).

Venus × Mars: physical and sexual attraction. Square or opposition create passion; trine and sextile create harmony. Without such aspects, the couple may be friendly but without spark.

Mercury × Mercury: how you communicate. If your Mercuries are in harmony, you understand each other in half words. If in tension, you spend years asking what exactly the partner meant.

Saturn × anything: Saturn is often referenced in couple synastry. Saturn of one person on personal planets (Sun, Moon, Venus) of another creates a sense of stability and obligation — but can also be a form of pressure. This is the classic indicator of a long marriage even without great passion.

Jupiter × anything: Jupiter is benevolent. Its aspects to partner's planets bring a sense of luck, optimism, growth.

After synastry the astrologer builds the composite chart — a third chart representing the couple itself as a separate entity. It's done by taking the midpoint between each planet of both partners.

The composite says not "you with your partner" but "we as a couple": what we are together before others, how we make decisions, where our focus is. Composite Sun in Sagittarius — we together love freedom and travel. Composite Moon in Cancer — we together nurture the home. Composite Mars in Aries — we together act fast and direct.

It's a powerful tool because it shows the couple as a third living entity, not a sum of two.

Why doesn't Couple BloomPrint stop at synastry? Because each system shows its own slice.

• Synastry — psycho-emotional field of the couple, how you communicate and feel
• BaZi — elemental interaction, "who feeds/controls whom" dynamics
• Jyotish Kuta — karmic thread, base compatibility
• Human Design — daily decision mechanics
• Numerology — your union's number, relationship year cycles

When all five show strong compatibility in one area — it's not coincidence, it's structural truth. When one system shows friction and others harmony — the one can be compensated. When three or more show friction in one theme — that's your real work as a couple.