At a total solar eclipse, the moment when the leading (eastern) limb of the Moon just touches the Sun’s eastern limb, and totality begins; or, at a total lunar eclipse, the point at which the Moon’s trailing limb becomes completely immersed in the Earth’s umbra. Second contact in a total solar eclipse may be immediately preceded by the appearance of Baily’s beads or the diamond ring. At an annular eclipse, second contact refers to the instant when the Moon’s trailing (western) limb leaves the Sun’s western limb, so that the whole of the Moon’s body is silhouetted against the Sun. The term is also used to describe the instant when a smaller body has completely moved in front of the disk of a larger body in an eclipsing binary or at a transit.