In 1926 John Alden Knight presumed some folk lore he found interesting and progressed to clarify and improve it, giving it the name Solunar (Sol for sun and Lunar for moon).
One by one the factors were examined and rejected. Three of them, however, merited further examination. They were sun, moon and tides. When the original research was being done only the approximate time of moon up - moon down were considered. Gradually, it became evident that there were also intermediate periods of activity that occurred midway between the two major periods. Thus the more evident periods were called for.
Intensity of activity also varies from day to day, according to conditions in general. If the barometer happens to be steady or rising, if the temperature is favorable (15 degrees higher than water temp) then long and active response to a Solunar Period can be expected. It is now known that the sun and moon are the two major sources of the astral energies that daily bombard the Earth and all her life forms. The closer they are to you at any given moment, the stronger the influence. All these energies that surround us, also aid in spiritual energy. Just as weather makes a difference in radio and TV reception, high energy aids in paranormal activity.
So the moon phases are important to ghost investigators, because obviously, when the moon is at a position where it is peaking high energy, then entities are easier detected.