Carl Jung brought a conclusion by studing 10000 charts.If one partner`s Sun conjucts other partner`s Moon withing the orb of 17 degrees-that is good and long lasting relationship.Golden marriage,so to say.10000 horoscopes is not a small number.
this is a very auspicious as they say aspect and traditionally a very very strong indication of compatibility for something as marriage - fit like a glove and like a bow with an arrow - not only conjunction of sun and moon but other sun moon aspects as well
regarding the aspect orb of 17 degrees - some astrologers use tight orbs and some say the lights, ie the sun and moon should have wider orbs for aspects than the other planets
some like linda goodman from what i have read never used orbs but only the signs to compare in planetary relationships
i personally go with both systems in that not using any orbs will still give you a feel for the essence of a pairing but the tighter the orb the stronger those energies playing out will be
just my personal opinion
I wish this story was 100% true but it has been taken out of context many times by astrologers. To summarize briefly, Jung was interested in this idea of synastry and hypothesized 3 aspects would be most salient: moon-sun, moon-moon and moon-ASC. Instead of waiting for all the charts to come in, he looked at batches of charts which supported his thesis. One batch supported the moon-sun hypothesis, another batch moon-moon etc. HOWEVER, when he analyzed them all at the same time, he discovered that the statistical evidence was much weaker, less convincing, much to his disappointment. Jung did however, concede that a moon conjunction was statistically significant in his experiment. Also, the number of charts was in the hundreds. A very large sample to be sure, but not nearly as good as analysing 10 000/5000 pairs!
In any case, this experiment was interesting in that Jung speaks about how "synchronicity plays havoc with statistical material."
The study is available in Jung's collected works, volume 18, titled "An Astrological Experiment" (1958). You can also find it in a book called "Jung on Synchronicity and the Paranormal."