A penumbral eclipse of the Moon occurs when the Moon moves into the penumbra created by the Earth’s shadow. The penumbra is a very weak shadow (unlike the umbra, which is the darkest part of the shadow) and the Moon does not dim perceptibly when in moves into the penumbra as seen by the human eye. Only sensitive instruments can determine the minute drop in the intensity of moonlight as the Moon enters the penumbra. Hence, it is very easy to overlook such eclipses. Its not a full eclipse. The Moon is only partically in the Earth's shadow.
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