The spookiest thing about a lunar eclipse is the eerie reddish color that covers the Moon. If Earth had no atmosphere, lunar eclipses would simply turn the shadowed part of the Moon jet-black. But Earth's air acts like a simple lens or prism. It bends part of the Sun's light into the shadow and stains this light a deep, ruddy copper color. In essence, what illuminates the Moon during a lunar eclipse is the light of every sunset and sunrise happening on Earth.
Experienced eclipse gazers try to guess how dark the shadow will be. With some eclipses, you see a pale amber Moon. But especially in years following big volcanic eruptions, the shadow can become so dark that the Moon virtually disappears, even when seen through a telescope. In 1883, the volcano Krakatau near Java exploded, sending several cubic miles of pulverized rock high into the atmosphere. At the next lunar eclipse several weeks later, the Moon all but vanished. Similarly, dark eclipses have followed other big eruptions, such as that of Mount Agung on Bali, which produced two "black Moon" eclipses in 1963 and 1964. More recently, a very dark eclipse followed the eruption of the Mexican volcano El Chichon in 1982.