Moon Illumination is a more specific description of the moon’s appearance than Moon Phase. Moon Illumination is the percent of the moon’s visible area illuminated by direct sunlight. At New Moon the percent illuminated is 0. At First and Last Quarters it is 50%. At Full Moon it is 100%.

Returned Value Units: Percent (between 0 and 100)
Observation Types: Day, Hour
Resource Families: Astronomical Data
API Versions: v1