Lunar Eclipse explained: Why don't we see the Lunar Eclipse every month? A blood moon occurs during a total lunar eclipse,the Earth comes between the Sun and the Moon, blocking direct sunlight from reaching the Moon. However, some sunlight still reaches the Moon, but it first passes through the Earth's atmosphere. The Earth's atmosphere filters out most of the blue light, allowing only the longer-wavelength red light to pass through and reflect off the Moon's surface. This scattering effect, sim