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.
The full moon is given different names, depending on when it appears: 1  January - Moon After Yule, Wolf Moon, or Old Moon. 2  February - Snow Moon or Hunger Moon. 3  March - Sap Moon, Crow Moon, Worm Moon or Lenten Moon. 4  April - Grass Moon, Frog Moon or Egg Moon. 5  May - Milk Moon or Planting Moon. 6  June - Rose Moon, Flower Moon, or Strawberry Moon.