When the aspects are formed between whole signs, but not by actual degrees within a 6 degree orb, they are important, but nowhere near as significant as an actual square aspect.
Sextiles and Trines, true to the common wisdom, are quite nice for synastry. They are exceptionally nice when the sextiles are within 5 degrees of orb, and when the trines are within 6 degrees of orb.
Sextiles have a bit more of stimulating feeling, and trines have a bit more of an "easy" feeling. In general, I'd take a nice conjunction as my first choice for excellent synastry, a trine second, and a sextile third.
Semi-sextile planets are placements that are one sign away from each other. For example, Moon in Taurus and Moon in Aries. This is probably the least well-understood aspect in synastry.
Basically, it is not at all good. Semi-sextile energies show completely opposite natures that really do not "get" each other. It's like someone who believes in polygamy with someone who believes in monogamy.
No comprende. An actual semi-sextile aspect, within about a three-degree orb is an especially problematic issue. A large number of semi-sextile planets is not at all good for compatible synastry. Check it out and you'll see what I mean. However, all of the above applies almost entirely to same-planet-to-same-planet semi-sextiles.
So having Moon and Sun in semi-sextile signs between two people may not be a big deal at all. But having Sun-Sun or Moon-Moon in semi-sextile will eventually be an issue between two people in real intimacy.
Quincunxes are probably the most confusing aspect in synastry. They tend to get a bad rap, which is partially quite well deserved.
However, an actual close quincunx between compatible planets such as Venus-Venus, Moon-Moon, Sun-Sun, or ASC-ASC is actually a very positive connection on the one hand, in addition to the problems of the quincunx on the other hand.
Quincunx planets have a "6-8" relationship with each other in astrology, which basically indicates an energy that is more heavy, "karmic," and dysfunctional.
The really unusual thing about a quincunx is that a close quincunx (of three degrees and fifteen minutes or less) between basically 'soft' planets actually give some very strong sign compatibility to counter-balance the problems of the quincunx signs. I have to thank the Magi Society's research for helping me to eventually put this puzzle together. Venus quincunx Venus within three degrees? Thank them lucky stars.
Another basic compatibility test is to see if two people are basically of the same astrological gender. Masculine people need masculine partners. Feminine people need feminine partners. Balanced people can go both ways, but are best with balanced partners. The more similar two people's astrological gender is, the more compatible they will be.
page 5 of 6