What are the four main phases of the moon?
The first quarter and third quarter Moons are referred to as “half Moons” and both occur in between the new and full Moons. Where as the new and full Moon occurs when the planets are approximately aligned in a row, the first and third quarter Moons occur when the Moon is at 90 degree angles with respect to the Earth and sun. So if the Sun was the top of a capital letter “L”, then the Earth would be at the bend in the letter and the Moon would be at the far bottom right end. From our perspective, we are seeing exactly half of the moon illuminated and half in shadow. The first and third quarter Moons are highest in the sky at sunset, and set six hours later.
Together, these four phases create the outline for a lunar phase cycle that begins with the new Moon, then first quarter, full Moon, and then finally to third quarter before starting again. With these four key phases identified, understanding the phases in between becomes much easier as they are based on the Moon gradually becoming more, and then less illuminated.