What a comparison chart is doing
Synastry is a method within astrology that compares two or more charts. A drawing may place the charts around the same wheel so that an astrologer can discuss relationships between their placements. In the vocabulary of the practice, these cross-chart angular relationships are often called interaspects.
This describes the method, not proof that it can determine compatibility. A comparison of Sun signs is a smaller exercise still: it leaves out most of the chart and, more importantly, the real experiences, preferences and behavior of the people involved.
Learn the layers before comparing them
Begin by reading one chart accurately. Identify a planet, its sign, its house if the time is known and any aspect you are discussing. Only then try to distinguish which placement belongs to which chart in a comparison drawing. Keep the color key and settings beside your notes.
Sun and Moon language, house overlays and aspects each supply a different kind of symbolic prompt. Do not combine several unfamiliar terms into a confident sentence. If you cannot explain the component, pause and return to the relevant beginner lesson.
Use conversation instead of a verdict
If both people want to explore a symbolic exercise, turn a proposed theme into an ordinary question about expectations or communication. Let each person answer from experience. A symbol cannot establish what another person feels, whether they are honest or whether a relationship should continue.
Avoid scores that imply a precise chance of success. A percentage generated from chart rules is not evidence of a measured relationship outcome. Likewise, a supposedly difficult aspect is not a reason to excuse harmful behavior or ignore something a person has directly told you.
Keep permission and privacy visible
Ask permission before using another person’s birth details. You can learn the mechanics with invented or clearly public example charts instead. Do not publish private information, assume an unknown birth time or fill a gap with a guess simply to complete a chart.
Finish a practice comparison with two columns: symbolic questions raised and actual information the people have chosen to share. Keep them separate. The exercise should leave room for disagreement and should never substitute for consent, communication or evidence about how people treat one another.