On Saturday (September 17) the Moon will enter its phase, called the last quarter, also called the third quarter, during which it will be half lit as seen from Earth.
Both the last quarter and the third quarter may initially be confusing names for this stage, as the Moon is half lit, but they actually refer to the fact that the Moon has completed 3/4 of its orbit around the Earth at this point.
The semi-illuminated moon will be visible over New York around 11:00 pm EDT (03:00 GMT September 18) and disappear from view at dawn on Sunday (September 18) around 6:19 am EDT. (10:19 GMT). At this time, the last quarter moon will reach an altitude of about 74 degrees above the horizon in the southeast (about seven fist-widths at arm’s length).
Related: Night Sky September 2022: What You Can See Tonight [maps]
During the lunar cycle, which takes about 29.5 days, the Moon is visible at different stages of illumination and at different times of the day.
In the last quarter, the moon rises around midnight and reaches its maximum height above the horizon around dawn. It is installed around noon.
During the phase of the lunar cycle, which includes the last quarter, the moon’s illumination decreases as its phase changes from full moon to new moon.
Related: What is the phase of the moon today? Moon phases 2022
The moon is said to be waning at this time as it transitions from a full moon—its brightest state—to its least illuminated stage, called a new moon. The illuminated side of the Moon is shrinking because its orbit is taking it out of our view from our perspective here on Earth.
The next stage of the lunar cycle after the last quarter is the waning crescent. At this point, the moon will be visible as nothing more than an arc of silver light as it has almost returned to the point in its orbit where it faces directly towards the sun.
This is followed by a new moon, when the illuminated side of the moon is fully facing the sun, which seems almost invisible from here on Earth. At this point, the moon rises and sets with the sun, which means that it is during the day. Thereafter, the illuminated side of the moon grows, and the moon begins to rise later each day, during which it is described as waxing, and continues until it is fully illuminated again at the next full moon.
The boundary between the light and dark sides of the moon is called the “lunar terminator” and during the last quarter it marks the moon’s sunset. On the other hand, during the first quarter, the lunar terminator shows the sunrise on the moon.
In both the first and last quarter, the lunar terminator is aligned with the Earth’s terminator line, which separates day and night on our planet.
The next lunar cycle begins with a new moon on September 25, with the next full moon on October 9, and then with the next last quarter moon rising on October 17.
Be sure to check out our guides to the best binoculars and best telescopes to see the last quarter moon. For the best pictures of the moon, check out our guide to photographing the moon, as well as our recommendations for the best cameras for astrophotography and the best lenses for astrophotography.
Editor’s Note: If you’re taking a last quarter moon photo and would like to share it with Space.com readers, please send your photos, comments, name, and location to spacephotos@.
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