Full moons make for a wonderful setting for criminal activity, as we find in detective novels. It's that night when the gruesome murderer commits the ghastly crime and is seen by a non-descript, aged neighbor. The neighbor's claim to credibility in the witness box is the fact that there was a full moon on the night in question and everything was there for all to see; it was only a matter of chance that he or she was the only one to spot it! Full moon nights also offer the perfect cover for the snooping detective to hide behind the bush with his dim-witted assistant in tow.
It makes sense, then, that the most potent example of astrological synastry (harmony between two birth charts) involves contact between one person's Sun and the other person's Moon, or contact between the two Moons. Carl Jung, the renowned Swiss Psychologist, famously conducted a 'marriage experiment' in which he studied the birth charts of over 500 couples. What he found was an unmistakable trend of Sun-Moon contact between partners. To most astrologers, this came as no surprise-it has long been understood that when one person's Moon hits another person's chart in a significant way, there exists a strong possibility of lasting and meaningful romance.
So here you have two definitions of a blue moon but the one for a calendar blue moon does not describe the true meaning of a blue moon. Here's why: