The First and Last Quarter phases happen when the Moon is exactly half illuminated, with 50-percent luminosity. The New Moon Phase occurs when the Moon is completely dark with zero-percent luminosity, while the Full Moon Phase is completely bright with 100-percent luminosity. These phases occur at very specific times and are measured by both the Moon’s luminosity and how far along the Moon is in its orbit around Earth. The four main Moon phases in order are the New Moon, First Quarter Moon, Full Moon and Last Quarter Moon. The illustration is set to your computer’s clock and therefore gives you an accurate reading for your own particular time zone. The illustration above shows the range of illumination for today - November 23, 2023. And while the changes may seem slow, on any given day the amount of Moon illuminated by the Sun can vary by as much as 10-percent. It’s the Moon’s journey as it orbits around Earth that creates the predictable dance between light and shadow.
