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Birthday · October 21, 2023

Quarter Moons

October 21, 2023

The story of your birthday began billions of years before calendars existed, in furnaces of light and clouds of dust.

Quarter Moons

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APOD published October 21, 2023. Credit: Marcella Giulia Pace. A publication-date match, not a photo taken on your date. Independent of NASA.

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Quarter Moons

Original APOD · October 21, 2023

Half way between New Moon and Full Moon is the Moon's first quarter phase. That's a quarter of the way around its moonthly orbit. At the first quarter phase, half the Moon's visible side is illuminated by sunlight. For the Moon's third quarter phase, half way between Full Moon and New Moon, sunlight illuminates the other half of the visible lunar disk. At both first and third quarter phases, the terminator, or shadow line separating the lunar night and day, runs down the middle. Near the terminator, long shadows bring lunar craters and mountains in to sharp relief, making the quarter phases a good time to observe the Moon. But in case you missed some, all the quarter phases of the Moon and their calendar dates during 2022 can be found in this well-planned array of telephoto images. Of course, you can observe a first quarter Moon tonight. International: Observe the Moon Night

Image credit: Marcella Giulia Pace

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