What are syzygy and quadrature?
The position of the Moon at Full and New Moon and the next can be divided into four parts, each part being called a quarter.
What are the features of each quarter?
During the first quarter, the New Moon changes into a crescent and then into a semicircle. During the second quarter, the semicircle changes into the circle of the Full Moon. During the third and fourth quarters, this sequence is reversed.
What is the main difference between quarters of the Moon and phases of the Moon?
Quarter of the Moon refers to the position of the Moon with relation to its orbit. Hence at the end of the first quarter, the Moon has completed one fourth of its orbit around the Earth.
Phase of the Moon refers to the appearance of the Moon when only a part of the Moon’s circle appears to be bright.
Hence half Moon occurs not at the end of the second quarter and again at the end of the third quarter.