Lunar Eclipses Explained: Why the Moon Turns Blood Red
The Alignment
A lunar eclipse occurs when the Earth passes directly between the Sun and the Moon, casting its shadow across the lunar surface. This can only happen during a full moon, when the three bodies are aligned in a straight line — a condition astronomers call syzygy. Unlike solar eclipses, which are visible only from a narrow path on Earth, a lunar eclipse is visible from the entire night side of the planet. Anyone who can see the Moon can see the eclipse.
The Earth casts two shadows. The penumbra is the outer, partial shadow where only some sunlight is blocked. The umbra is the inner, total shadow where the Earth completely obscures the Sun. A penumbral eclipse is subtle — the Moon dims slightly but remains visible. A partial umbral eclipse takes a bite out of the Moon. A total lunar eclipse drenches it in red, and a near-total one — like the August 28, 2026 event — covers roughly 95 percent of the Moon in umbral shadow.
Why Red
If the Earth blocks all direct sunlight, why does the Moon not simply disappear? The answer is atmospheric refraction. Sunlight passing through the Earth's atmosphere is bent — refracted — around the planet's edge and projected onto the Moon. The atmosphere scatters shorter blue wavelengths, exactly as it does during a sunrise or sunset, leaving only the longer red and orange wavelengths to reach the Moon. The result is the "blood moon" — a copper-red lunar disk that is one of the most striking sights in astronomy.
The exact shade depends on atmospheric conditions. Volcanic ash, dust storms, and pollution in the Earth's atmosphere can darken or deepen the red. Each eclipse is slightly different, and predicting the exact color is impossible until the event unfolds.
The Eclipse of August 2026
The lunar eclipse of August 28, 2026, is notable for two reasons. First, it is a near-total eclipse, with 95 percent coverage, meaning only a thin sliver of the Moon's southern edge will escape the umbra. This creates a dramatic visual effect — a blood-red Moon with a bright rim, like a celestial eye. Second, it occurs in the early morning hours over Central Europe, with the Moon low in the western sky near moonset. For German observers, this means the Moon will appear larger due to the moon illusion — the optical effect that makes the Moon look bigger near the horizon — and will set while still partially eclipsed.
The next total lunar eclipse visible from Central Europe will not occur until 2028, making this the most accessible deep eclipse for German skywatchers for several years. Unlike solar eclipses, lunar eclipses require no protective equipment. The naked eye, binoculars, or a small telescope all provide excellent views.
The Edge Review explains science for general readers. Eclipse timings for specific locations are available from timeanddate.com and local astronomical societies.