Dusk - online puzzles

Dusk

Dusk occurs at the darkest stage of twilight, or at the very end of astronomical twilight after sunset and just before nightfall. At predusk, during early to intermediate stages of twilight, enough light in the sky under clear conditions may occur to read outdoors without artificial illumination; however, at the end of civil twilight (when Earth rotates to a point at which the center of the Sun's disk is 6° below the local horizon), such lighting is required to read outside. The term dusk usually refers to astronomical dusk, or the darkest part of twilight before night begins.