If the weather is good, viewers across the UK will be treated to a partial solar eclipse on 21 August 2017, just before sunset. In a partial eclipse, a small bite out of the Sun can be seen at the mid-eclipse point, as it is covered by the Moon. A partial solar eclipse is a fascinating natural phenomenon, but is not of any practical scientific use, unlike a total eclipse which provides a special opportunity for studying the solar corona – the tenuous layers of hot gas around the Sun which are much fainter than the familiar yellow disk.