according to epedia
"The mana provided by the sun is relatively constant and provides a slow but steady mana growth as the magicians skill advances. It is far from the most dominant source of Lunar mana and, in fact, is not even perceivable by novice mages."
If this is the case, may we make it so that it is perceivable by moonmages of a certain circle or who have a certain number of ranks in attunement?