Studying the mysteries of the corona is not easy, for the same reason that looking at the sun itself isn't easy: the brilliance of the solar fires washes out everything else. Coronagraphs — black masks fitted in telescopes and other observing instruments — can cover up the solar disk and allow astronomers to focus just on the plasma. But diffraction of the incoming light makes the pictures imperfect. It is only during a total eclipse, when the moon itself acts as the greatest coronagraph of all, that a truly good look at the corona becomes possible.