With a telescope, you can watch the edge of the umbra slowly engulfing craters, mountains and lunar maria (the darker plains on the moon's surface), as your local night sky slowly and progressively gets darker.Take note of the Pleiades star cluster, which will be situated high above the moon, becoming more prominent as the eclipse progresses.These hues are caused by sunlight skimming and bending through Earth's atmosphere: it's the combined light of all the sunrises and sunsets that ring our world at any given moment.But if a major volcanic eruption has recently polluted the atmosphere with an aerosol cloud or a thin global haze, the eclipse will be ashen gray, or almost black.The Agung volcano in Indonesia in 1963 and Pinatubo volcano in the Philippines in 1991 were the primary reasons for the lunar eclipses that followed in the wake of their eruptions for being so dark."