Vacuum in the manifold drops as engine demand increases. If you use ported vacuum you always have a vacuum signal. If you want to make adjustments it can be done using the advance pot on the distributor when you use ported vacuum.
The decreasing or waning phases are when the moon shrinks from the full moon down to the new moon (darkness). As the moon wanes during the 3rd and 4th quarters, this is a good time to prune plants, as the water table is diminishing and so less sap will flow out of the cut ends.
Noun. 1. phase of the moon-a time when the Moon presents a particular recurring appearance. phase - (astronomy) the particular appearance of a body's state of illumination (especially one of the recurring shapes of the part of Earth's moon that is illuminated by the sun); the full phase of the moon.alf-moon-the time at which the Moon is at first or last quarter when half its face is illuminated. full, full moon, full phase of the moon, full-of-the-moon-the time when the Moon is fully illuminated; the moon is at the full.