How to Compare Synastry Charts Without Changing the Rules

Imagine the same couple receiving three different answers

Imagine Maria and Alex comparing a synastry report after a good first date. One report calls Maria's Venus and Alex's Mars a sextile. Another calls them a conjunction. A third drops the contact altogether. The couple isn't looking at three relationships. They're looking at three methods.

Ask what changed. Was it the zodiac reference, the supplied degree, the aspect list, the orb, or the chart order? Once you separate those choices, the disagreement becomes readable.

This is a fictional example, not a calculated birth chart. We’ll use it as a worksheet. Every contact will be marked confirmed by degree, suggested by sign, or unresolved because a needed input is missing.

Name the zodiac frame before you name the signs

The zodiac system is the reference frame used to name a planet's position. The tropical zodiac begins at 0 degrees Aries, tied to the vernal equinox. A sidereal zodiac uses a stellar reference and requires an ayanamsha, the value used to describe the separation between the two frames. Because the reference frame changes the sign labels, write the chosen system down before you compare placements.

Write Tropical, or write Sidereal and name the ayanamsha. Do not let one chart use tropical signs while the other uses sidereal signs. If you want both traditions, run two labeled comparisons with separate placements, results, and conclusions.

A sign change is possible when a position is close enough to a boundary, but you cannot convert it by eye. The ayanamsha changes with the date and the chosen reference, so a real conversion needs both. With supplied placements, record the system already used rather than guessing a new sign.

A sign change can alter the sign story without giving you permission to blend systems. Keep the two readings beside each other if you want to compare traditions. Keep them separate if you want to know which symbolism belongs to which method.

Sources: Sidereal, Skyscript Glossary; An Introduction to Aspects and Chart Shaping in Natal Astrology, Skyscript

Freeze the inputs and the order of the charts

Before interpreting chemistry, copy the raw inputs into a short record. For each person, note the planet, sign, degree, minutes if known, zodiac system, and source of the placement. Venus at 27°40′ Gemini supports a degree comparison. Venus in Gemini with no degree supports a sign discussion, but it cannot prove a one-degree contact.

Keep the people in a fixed order. Call them Person A and Person B. Write Person A's Venus to Person B's Mars, not just Venus-Mars. The geometry is mutual, but the planet owners help you describe how each person participates in the contact.

If a Moon degree is missing, mark the contact unresolved. You can still read the Moon signs. You cannot claim a close Moon aspect. If a placement is rounded to a whole degree, preserve that limitation. A listed 13° supports less precision than 13°18′.

Sources: Aspects Between Charts, Cafe Astrology; An Introduction to Aspects and Chart Shaping in Natal Astrology, Skyscript

Use this worksheet before you interpret the story

Here is the Maria-and-Alex worksheet. It uses tropical positions, the five major aspects, a six-degree orb, and Moon, Venus, and Mars only. The numbers are illustrative inputs, not birth-chart results.

Settings: tropical zodiac; Person A is Maria; Person B is Alex; planets are Moon, Venus, and Mars; accepted angles are 0°, 60°, 90°, 120°, and 180°; maximum orb is 6°; statuses are confirmed, sign-based, and unresolved.

Row 1: Maria Venus 27°40′ Gemini equals 87°40′. Alex Mars 3°10′ Virgo equals 153°10′. The shorter distance is 65°30′. The nearest selected angle is 60°, so the contact is a sextile with a 5°30′ orb. Status: confirmed, boundary-level within this method.

Row 2: Maria Moon in Cancer, degree unknown. Alex Venus 14° Libra. A sign-only comparison can describe the signs, but no degree aspect can be confirmed. Status: unresolved for aspect geometry.

Row 3: Maria Mars 12° Leo. Alex Venus 13° Aquarius. The shortest distance is 179°, a one-degree opposition. Status: confirmed and close.

The ranking is now visible. The close Mars-Venus opposition comes first. The 5°30′ Venus-Mars sextile comes second. The Moon-Venus line stays outside the degree ranking until Maria's Moon degree is known.

Sources: An Introduction to Aspects and Chart Shaping in Natal Astrology, Skyscript; Aspects Between Charts, Cafe Astrology

Choose the aspect list and orb policy before scanning for contacts

An aspect is the angular distance between two chart factors. The usual major set is conjunction at 0°, sextile at 60°, square at 90°, trine at 120°, and opposition at 180°. Skyscript distinguishes these five major aspects from minor aspects such as the quincunx and semisquare.

Use the five major aspects first. A minor aspect may become a useful second pass, but it should not appear only because the major contacts fail to produce a tidy story. If you add quincunxes, parallels, asteroids, or other points, name the addition and give it a place in the ranking. Do not double-count Maria's Venus to Alex's Mars and Alex's Mars to Maria's Venus. They are one geometric row.

An orb is the distance between an actual contact and its exact angle. Traditions differ, including practices that give the luminaries wider allowances. This guide chooses one practical boundary: six degrees for the five major aspects. That boundary does not make every qualifying contact equally strong. A conjunction at 0°45′ sits above a square at 5°30′, and a trine at 1° deserves more attention than a sextile at 5°50′.

Do not widen the orb because the preferred story needs another contact. If your tradition uses different allowances, declare them first and apply them to comparable rows. The boundary gives the report consistency; the ranking gives it proportion.

Sources: An Introduction to Aspects and Chart Shaping in Natal Astrology, Skyscript; Orbs (or rays), Skyscript Glossary

Calculate the shortest distance, not the convenient one

Convert each supplied placement to a position from 0° to 360°. Aries begins at 0°, Taurus at 30°, Gemini at 60°, and so on. Add the degree within the sign. Subtract the two positions, then use the shorter route around the circle. If the difference exceeds 180°, subtract it from 360°.

In the worksheet, Maria's Venus is 87°40′ and Alex's Mars is 153°10′. Their difference is 65°30′, which is 5°30′ from the 60° sextile. The arithmetic gives the aspect its name.

Now change only Maria's placement. If her Venus were 27°40′ Leo, it would sit at 147°40′. Alex's Mars would then be 5°30′ from a conjunction. Same frame, aspect list, and orb. Different supplied position, so a different contact.

Watch the Pisces-Aries boundary. A planet at 29° Pisces is close to 0° Aries on the circle, even though the sign labels look far apart. Check the positions first.

Sources: An Introduction to Aspects and Chart Shaping in Natal Astrology, Skyscript; Orbs (or rays), Skyscript Glossary

Keep sign relationships and degree aspects in separate columns

A sign relationship describes the twelve-sign pattern. A degree aspect measures the actual angular distance and tests it against the declared orb. Both belong in astrology. They do different work.

A pair can suggest a trine by sign while forming a square by degree. Consider one Moon at 28° Leo and another person's Venus at 2° Sagittarius. The signs are both fire signs, but the positions are 94° apart. Under a six-degree policy, that is a square at 4° from exactness. Write degree-based square, fire-sign trine by element.

The reverse can happen too. A Moon at 29° Taurus and Venus at 1° Libra are 122° apart, a close trine by degree, although Taurus and Libra do not make a trine by element. Read the measured trine, then let the sign difference describe its style.

Use clear labels: by sign, within a six-degree orb, and unresolved. A sign pattern can guide the background. A degree-confirmed aspect can lead the ranking. A missing degree stays open.

Sources: An Introduction to Aspects and Chart Shaping in Natal Astrology, Skyscript; Orbs (or rays), Skyscript Glossary

Read the planet pair before the sign story

The aspect tells you how two functions meet. The planets tell you what meets. The Moon speaks to instinctive feeling, comfort, and reception. Venus speaks to affection, attraction, taste, and values in closeness. Mars speaks to pursuit, desire, heat, and action under pressure. These are interpretive roles, not fixed labels.

Start with owner, planet pair, aspect, and orb. Then add the signs. A close Venus-Mars opposition may describe strong attraction with different approaches to pursuit. A Moon-Venus conjunction may join emotional comfort and affection. A square may create friction that asks for conscious handling. A flowing aspect may feel natural without guaranteeing that both people want the same thing.

The strongest exception is a tight hard contact beside a loose easy one. The hard contact may be more visible because it is closer to exactness. That does not make it better or worse. It makes it active. Cafe Astrology's synastry guidance likewise treats planet owners, sign placement, and the interchart relationship as parts of the same reading.

Group repeated themes. If several close contacts involve Venus, affection is probably a major thread. If one wide contact supports a sweeping claim, lower the claim.

Sources: Aspects Between Charts, Cafe Astrology; An Introduction to Aspects and Chart Shaping in Natal Astrology, Skyscript

Add houses or minor aspects only when the inputs support them

A house overlay answers a different question: where one person's planet falls in the other person's chart. It needs house cusps and therefore reliable birth-time information. A placement-only report using supplied Moon, Venus, and Mars signs with optional degrees should not imply houses it did not calculate.

Minor aspects can add texture. So can outer planets, angles, parallels, receptions, and other techniques. Each addition needs its own input and its own place in the method. A close Venus quintile may refine a reading, but it should not outrank a close Moon-Venus conjunction simply because it sounds unusual.

Write the scope plainly. This comparison reads supplied placements and optional degrees. It does not calculate natal positions from birth details, houses, or a complete chart. If you want a second layer, label it as a second layer.

Two reports can both be internally coherent and still fail to match. One may include houses and asteroids. Another may show only five major aspects. Compare shared inputs first, then describe what the extra layer adds.

Sources: Aspects Between Charts, Cafe Astrology; An Introduction to Aspects and Chart Shaping in Natal Astrology, Skyscript

Turn the highest-ranked contact into a useful next question

A consistent comparison should leave you with a question you can observe in the relationship. In the worksheet, the close Mars-Venus opposition leads. Ask how each person wants desire, initiative, pause, and refusal to be expressed. The wider sextile is useful context, not a rival headline.

For Maria and Alex, the result has three clean lines: a close confirmed Mars-Venus opposition, a wider confirmed Venus-Mars sextile, and an unresolved Moon-Venus aspect because Maria's Moon degree is missing. That is enough to start a conversation without pretending the missing input is known.

If a later report changes the answer, save the first settings, label the second method, and name the changed input. Do not blend the versions. Circle the strongest confirmed contact, write one ordinary question about it, and decide which method answers the question you actually have.

Sources: Aspects Between Charts, Cafe Astrology; An Introduction to Aspects and Chart Shaping in Natal Astrology, Skyscript

A little more clarity