A planet is said to be void of course when it is not aspecting any other planet. The term void of course is usually applied to the moon and refers to the period of time when the moon is no longer aspecting any planets in the last sign it was in but has not aspected any planets in the sign it will go into next. This void of course period may last only a few minutes or it may last several hours to a day. During this time, the moon is still in its previous sign, though some treat this period as if the moon is in no sign at all.
According to the definition of Void of Course which has been used since Medieval times, the void of course period begins as soon as the moon completes its final aspect with any planet in the sign it is passing through and ends the moment the moon aspects a new planet in the new sign.
Void of Course in Magick
During the void of course period, it can be said that no major planetary energies are dominant and available to affect your magical workings. Some believe that working magic during this time will yield, at best, no results and at worst chaotic and unpredictable results. However, other schools of thought see the void of course period as a time when there is nothing to interfere with your magical or mundane workings or when it is easier to be subtle, allowing your actions to go under the radar.
There is a rumor U.S. President Ronald Reagan, who was known to consult astrologers, was careful to take actions that might be unpopular with his constituents during the void of course periods.