The Moon is a major player in all horary work. She shows us the sequence of events that have come to pass or that will pass for any single interrogation. Because of this, we are told to pay special attention to the aspects she will make to show us the likely outcome of the question. Unfortunately, there is a time when she does not make any further aspects and the events likely peter out in the same manner as something that is no longer being pulled along. This is the dreaded Void of Course Moon.
When the Moon is Void, Lilly tells us “you will find that events do not go handsomely forward”, which implies a certain amount of struggle and discontinuity. For a Void Moon, I like to imagine a trapeze artist leaping from swing to swing with each swing being the perfection of an aspect with another planet. What happens when there are no more swings to jump to or when the next swing is too far to make? The swing’s momentum eventually comes to a stop, much like the events of the horary. There are many different interpretations for a Void Moon, and they are all dependent on the context of the question, but a good rule of thumb is that the matter simply stops moving forward, or the querent puts forth so much effort trying to obtain the matter, that they come to realize it wasn’t worth it.
There are two different sets of rules that define what a Void of Course Moon actually is. The first is a more “traditional” rule which states that the Moon must simply be within orb of an applying aspect with some other planet before she leaves a sign. The keyword here is “applying”, the aspect does not have to perfect within that same sign and can perfect in the next. There only has to be that interlocking of orbs of influence to keep the Moon on course. Moon at 26° Leo applying to a Trine of Saturn at 4° Taurus is not a Void Moon as they are within orb.
The more modern definition is that the Moon must be within orb of a planet and complete that aspect within the same sign. The example given in the preceding paragraph would have been an example of a Void of Course Moon using this definition of the term. Lilly himself used the “traditional” definition and there are several of his example charts where he continues to read off of the Moon’s aspects even if there is a shift in signs in order to perfect them. Some of these example charts even perfected and manifested.
There is, of course, one exception to the Void rule. Lilly shares with us that the Moon is much less impeded when she is in Cancer, Taurus, Sagittarius, or Pisces and may be able to continue on the influences by her own gumption in those signs through the blessings of the benefics Jupiter and Venus. Essentially, the Moon cannot be Void in those signs, but merely “technically Void”. The difference is that a Void Moon in these signs does not show an absolute loss of momentum, but merely a quiet period in the horary until the issue is continued later. Below is an example of a technically Void Moon. The Moon’s last aspect was a Sextile to Jupiter, but she has since moved out of orb of the separation and is not within orb of anything at this time. All in all, a very lethargic, dead horse type horary showing no movement. However, because of the Moon’s placement in Pisces, she is able to continue through and apply a Trine to Mars in Leo.
The Void of Course Moon can also be used for storytelling purposes regarding the situation surrounding the question or it can be overlooked entirely to fulfill such matters. Since the Moon’s last aspect shows the last thing to happen regarding a question, it doesn’t matter how far away that last aspect was, it is still significant. In his horary “A ship at sea in what condition?”, Lilly uses the Moon’s last Square with Saturn to show the last thing that happened to the ship. The problem is that the Moon and Saturn are 26° separated from their perfection of the Square, but that was the last aspect she made, and that’s what Lilly had to work with. He then uses the long Void period before the Moon began applying to another aspect to show that there had been no news or no story.
A final thought on the Void of Course Moon, in the way that Lilly utilizes them in his practice, he does not regard sign boundaries as being cutoffs of planetary influence. He sees them more along the lines of conditions. If the Moon changes signs to complete an aspect, it implies a change in her condition that must happen as a foreshadowing to the manifestation of the aspect. In other words, before whatever aspect perfects, something about the situation must change, this is especially important if the next aspect shows the perfection of the matter inquired about.