A corona (Latin,' crown') is an aura of plasma that surrounds the Sun and other stars. The Sun's corona extends millions of kilometres into space and is most easily seen during a total solar eclipse, but it is also observable with a coronagraph. The word corona is a Latin word meaning "crown", from the Ancient Greek (korone, "garland, wreath").

Based on this passage, when can the sun's corona best be seen? Let's think fast. Stream of consciousness:
To answer this question, we should know that: The Sun's corona extends millions of kilometres into space and is most easily seen during a total solar eclipse, but it is also observable with a coronagraph. So the final answer is during a total solar eclipse.