Earth’s Shadow Will Cover 96% of August Moon, Leaving Bright Rim
Sunlight will take an atmospheric detour before reaching the moon on Aug. 27 and 28. As the full moon moves through Earth’s dark central shadow, shorter blue wavelengths will scatter more readily in the atmosphere while some red and orange light is refracted toward the lunar surface. That filtered illumination can turn most of the moon copper-red.
The color will not cover everything. At maximum eclipse, approximately 96% of the lunar disk is expected to be inside the umbra, leaving a narrow, bright rim outside the darkest shadow. That remaining sliver is the geometric boundary separating this deep partial lunar eclipse from a total one.
NASA’s August skywatching guide confirms that the full moon will pass through Earth’s shadow overnight on Aug. 27-28, with much of North and South America and parts of Europe and Africa in the visibility region. NASA describes about 93% of the moon’s diameter as entering the umbra, while eclipse descriptions based on the covered portion of the disk give a figure of roughly 96%. Both describe the same essential view: nearly the entire moon darkened, but not completely covered.
Why the moon can turn copper-red
Earth blocks direct sunlight from reaching the section of the moon inside the umbra. The shadow is not necessarily pitch-black, however, because Earth’s atmosphere acts as a large optical filter and refracting layer around the planet’s edge.
Blue light is scattered more efficiently as sunlight passes through the atmosphere. The longer red and orange wavelengths are more likely to continue through and be bent into the shadow. NASA planetary scientist Sarah Noble has compared the resulting color to all of the sunrises and sunsets on Earth at that moment reflected off the surface of the Moon.
The exact appearance is not guaranteed. Atmospheric conditions and the observer’s local sky can affect whether the eclipsed region looks rusty orange, copper-red or simply dark. Haze and clouds can also erase the view entirely. What should remain visually distinctive under clear conditions is the contrast between the dim umbral region and the thin portion still receiving direct sunlight.
When to look from the United States
The full eclipse sequence, including the subtle passage through Earth’s lighter outer shadow, is expected to run from about 9:23 p.m. Eastern time on Aug. 27 until 3:01 a.m. on Aug. 28. The more obvious partial phase begins around 10:33 p.m. Eastern, reaches maximum coverage at approximately 12:12 a.m. and ends at 1:52 a.m.
For Central time, those key partial-phase moments are approximately 9:33 p.m., 11:12 p.m. and 12:52 a.m. Mountain time observers can look for the partial phase from about 8:33 p.m. to 11:52 p.m., with maximum coverage near 10:12 p.m. On the West Coast, the corresponding times are approximately 7:33 p.m., 9:12 p.m. and 10:52 p.m. on Aug. 27. Local moonrise and horizon conditions will determine how much of the sequence is visible from a specific site.
The Americas are generally well positioned because the eclipse occurs during nighttime hours across much of the region. Observers in Western Europe and West Africa may also see part of it, although the moon can be low toward the horizon and approaching moonset around dawn.
No eclipse glasses are needed
Unlike a solar eclipse, a lunar eclipse is safe to view directly. No eclipse glasses, filters or other eye protection are required because observers are looking at reflected moonlight rather than directly at the sun.
The event is visible with the naked eye. Binoculars or a small telescope can improve the view of Earth’s curved shadow and make the sharp contrast along the remaining bright rim easier to resolve. A clear view toward the moon matters more than magnification.
That slim illuminated edge is also the defining feature of the night: Earth’s shadow will encompass almost the whole lunar face, but the alignment will stop just short of totality.
By David Whitaker — Associate editor for AMI’s aerospace and drone systems desk, translating flight systems, aircraft programs, spaceflight, and UAV developments into accessible technical stories.
