dusk - choose a jigsaw puzzle to solve

Dusk occurs at the darkest stage of twilight , or at the very end of astronomical twilight after sunset and just before night . Pre-dusk, during early to intermediate stages of twilight , there may be enough light in the sky under clear conditions to read outdoors without artificial illumination, but at the end of civil twilight , when Earth rotates to a point at which the center of the Sun is 6° below the local horizon , artificial illumination is required to read outside. The term dusk usually refers to astronomical dusk, or the darkest part of twilight before night begins.