本文介绍了月球的周期性变化，即月相。月球绕地球公转，太阳光照射角度的变化导致我们在地球上看到月球被照亮的部分不同，从而形成新月、娥眉月、上弦月、盈凸月、满月、亏凸月、下弦月、残月这八种月相。整个月球周期约为29.5天。文章还提供了当前（8月16日）的月相为“下弦月”，月球表面有46%被照亮，并列举了不同观测设备（肉眼、双筒望远镜、望远镜）可观测到的月面特征，如环形山和高原，并预告了下一次满月日期。

🌕 月相是月球绕地球公转过程中，太阳光照射角度变化导致我们在地球上看到月球被照亮部分的不同形态，构成一个约29.5天的周期性循环，包含新月、娥眉月、上弦月、盈凸月、满月、亏凸月、下弦月、残月八种主要形态。

🔭 当前（8月16日）月相为“下弦月”，月球表面有46%被照亮，标志着月球可见度将逐渐降低，但仍可观测到如阿里斯塔克斯高原、第谷环形山和哥白尼环形山等月面特征。

🔭 通过双筒望远镜可观测到更精细的月面细节，包括阿基米德环形山、阿尔方斯环形山和克拉维乌斯环形山等；使用望远镜则能看到阿波罗12号着陆点、莱纳尔伽玛和席勒环形山等更为复杂的月表结构。

📅 下一次满月将在9月7日出现，而上一次满月则在8月9日。

The moon is half lit up tonight, which means a lot of things. Namely, we're in a new lunar cycle.

The lunar cycle is a series of eight unique phases of the moon's visibility. The whole cycle takes about 29.5 days, according to NASA, and these different phases happen as the Sun lights up different parts of the moon whilst it orbits Earth. 

So, what's happening with the moon tonight, Aug. 16?

What is today’s moon phase?

As of Saturday, Aug. 16, the moon phase is Third Quarter (also known as the Last Quarter) and it is 46% lit up to us on Earth, according to NASA's Daily Moon Observation.

From this point onwards, the moon will be less and less visible, as we're now on day 23 of the lunar cycle. But there's still plenty to spot on the moon's surface, if you look hard enough. With your naked eye, catch a glimpse of the Aristarchus Plateau, the Tycho Crater, and the Copernicus Crater.

With binoculars, see even more, including the Archimedes Crater, Alphonsus Crater, and the Clavius Crater. If you have a telescope, look out for the Apollo 12, Reiner Gamma, and the Schiller Crater, too.

When is the next full moon?

The next full moon will be on Sept. 7. The last full moon was on Aug. 9.

What are moon phases?

According to NASA, moon phases are caused by the 29.5-day cycle of the moon’s orbit, which changes the angles between the Sun, Moon, and Earth. Moon phases are how the moon looks from Earth as it goes around us. We always see the same side of the moon, but how much of it is lit up by the Sun changes depending on where it is in its orbit. This is how we get full moons, half moons, and moons that appear completely invisible. There are eight main moon phases, and they follow a repeating cycle:

New Moon - The moon is between Earth and the sun, so the side we see is dark (in other words, it's invisible to the eye).

Waxing Crescent - A small sliver of light appears on the right side (Northern Hemisphere).

First Quarter - Half of the moon is lit on the right side. It looks like a half-moon.

Waxing Gibbous - More than half is lit up, but it’s not quite full yet.

Full Moon - The whole face of the moon is illuminated and fully visible.

Waning Gibbous - The moon starts losing light on the right side.

Last Quarter (or Third Quarter) - Another half-moon, but now the left side is lit.

Waning Crescent - A thin sliver of light remains on the left side before going dark again.