The moon will reach its last quarter phase on Tuesday (Aug. 8) when it will be half illuminated by the sun.
From New York City, the last quarter moon — also known as the third quarter moon — will be visible from 11:30 p.m. EDT (03:30 GMT) shortly after it rises, according to In the Sky. The half-illuminated moon will be visible until shortly before it drops below the horizon at around 1:46 p.m. EDT (1756 GMT) on Wednesday, Aug. 9.
The last quarter moon occurs at the point in the 29.5 lunar cycle at the halfway point between the fully illuminated full moon and the completely dark new moon. The last full moon, August’s Sturgeon Moon, occurred on Aug. 1, and the next new moon will happen on Aug. 16. This will also mark the start of a new lunar cycle.
Following the Sturgeon Moon, the illuminated side of the moon has been receding, with this progression called “waning” by astronomers. In addition to the illuminated lunar face shrinking, the moon has been going through other changes that will also culminate with the new moon. In particular, it has been rising and setting an hour later each day, meaning it is visible for a shorter time each night prior to the sun rising.
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The full moon generally rises at sunset and sets at sunrise, but by the new moon, this has been reversed so the moon rises around the same time as the sun and sets with our star. As a result, at the time of the new moon, it is mostly absent from the night sky.
This progression is partially turned on its head following the new moon. The illuminated face of the moon grows or “waxes” while the moon continues to rise and set an hour later each day.
The last quarter moon phase isn’t the only time in the 29.5-day lunar phase during which the moon is half-illuminated. There is an analog to the last quarter moon that falls exactly between the new moon and full moon called, maybe predictably, the first quarter moon. During the first quarter moon, the opposite side of the lunar face is illuminated compared to the last quarter moon. Which side of the moon an observer sees illuminated depends on which hemisphere of the Earth they are located, however.
If you are hoping to catch a look at the moon during its last quarter phase, our guides to the best telescopes and binoculars are a great place to start.
If you’re looking to snap photos of the moon or just the night sky in general, check out our guide on how to photograph the moon, as well as our best cameras for astrophotography and best lenses for astrophotography.
Editor’s Note: If you snap an image of the last quarter moon, and would like to share it with Space.com’s readers, send your photo(s), comments, and your name and location to spacephotos@space.com.
