That's not a synastry chart. Synastry is both people's birth charts, one inside the other. What you posted is just one chart. Probably a composite chart: that's what you get if you find the midpoints of every placement in both people's charts. The composite moon is the midpoint between your moon and your partner's, the composite Mars is the midpoint between your Mars and his Mars, and so on.
Synastry, not composite, is what you need to get a sense of the relationship dynamics. A composite chart is about the relationship itself, as an entity. Not about how you experience it, but about what comes of the relationship itself.
To cast an accurate composite chart, you have to know the accurate birth information of both parties. If you don't know his exact time and/or place of birth, you can't cast a composite chart. You can do a synastry chart without being certain of birth time, but it wouldn't have accurate houses, and the moon could be off by up to six degrees.
