Earth's shadow (or Earth shadow)

Earth's shadow cast onto the atmosphere can be viewed during the "civil" stage of twilight, assuming the sky is clear and the horizon is relatively unobstructed. The shadow's fringe appears as a dark bluish to purplish band that stretches over 180° of the horizon opposite the Sun, i.e. in the eastern sky at dusk and in the western sky at dawn. Before sunrise, Earth's shadow appears to recede as the Sun rises; after sunset, the shadow appears to rise as the Sun sets.
Earth's shadow is best seen when the horizon is low, such as over the sea, and when the sky conditions are clear. In addition, the higher the observer's elevation is to view the horizon, the sharper the shadow appears.

Canon SX730 HS