Bibliography

[John Cribati]

Actually they don't loose their powers, they just become weaker. The exact wording was "... their powers weaken the further it is to a full moon." As such, they would actually be at the half way point for power during a new moon, and weakest directly after a full moon.

Owrtho

Not really, The moon waxes and wanes. It's like filling a cup with water and then slowly pouring the water out, then filling it again. The highest power comes when it's full, and the least when it's empty.