Total solar eclipses are visible when the Sun, Moon and Earth are in line, and the Moon is close enough for its shadow to reach the surface of the Earth. Anyone within the darkest part of the shadow - the umbra - briefly sees a total solar eclipse where the Moon completely covers the solar disk. During totality the spectacular outer atmosphere of the Sun - the corona - becomes visible. In locations outside of the umbra, but within the penumbra, the Sun is partially covered by the Moon in a partial solar eclipse. Here the image of the partial eclipse is as it appears through a safe filter, and the image of the total eclipse is unfiltered.
RAS/Lucinda Offer