Theoretically, it's best to have the enemy between you and the moon, you look at the enemy and see the moon so you are in the darker side relative to the enemy. The contrary is bad for you, the bigger the moon phase. But I doubt that SH3, SH4, SH5 will consider this for the convoys or escorts to spot you more easily, in Aces of the Deep (an early sub sim) this is actually a factor
