Eclipse Contact Times

Contact times are the moments that mark the stages of an eclipse, named after the instants when the edges of the two discs touch. A solar eclipse has up to four. First contact, C1, is when the Moon's edge first touches the Sun's and the partial eclipse begins. Second contact, C2, is when the Moon fully covers the Sun and totality begins, or at an annular eclipse, when the Moon's disc fits entirely inside the Sun's and the ring is complete. Third contact, C3, ends totality or annularity, and fourth contact, C4, is when the Moon's edge leaves the Sun and the eclipse is over. Between second and third contact comes the moment of greatest eclipse. A partial eclipse has only first and fourth contact, because from there the Moon never fits within the Sun's disc. Lunar eclipses use their own labels for Earth's shadow: P1 and P4 when the Moon enters and leaves the penumbra, U1 and U4 for the umbra, and U2 and U3 for the start and end of totality. Solar contact times differ from place to place, which is why every city page on Orbital Radar gives its own, to the second. They matter most for safety: at a total eclipse, eclipse glasses come off only after second contact and go back on at third.