Mana

The largest moon to the planets surface, it is always in full moon state.   Legends say that the moon Mana seeps with arcane power which is what lead to people establishing the arcane arts in the first place. It was also rumored to be the beacon that lead the visitors who came during the arrival.   While it doesn't follow a new moon - full moon cycle, due to it's own luminescence, it does follow a monthly rotation.  With it's slow speed across the sky it's only visable for approximately 15 days of the month.   It stays mostly stationary in the night sky, and can be visible during the day as it makes it's slow trek across the sky.  While extremely rare, it can eclipse the during the day, and when that happens the eclipse can last 3-4 hours.  During the zenith of one of these eclipses magic in it's entirety ceases to function.  For this reason, many scientists have worked at perfecting the predictions of these events to ensure that all machinery that relies on magic is disable prior to these events to prevent catastrophe.