Civil twilight is when the Sun is 6 degrees or more below the horizon. It is also known as dusk or dawn in some places and is the time immediately before sunrise and right after sunset. During this period of time, there is still enough light from the Sun that artificial sources of light are not needed to carry on outdoor activities in most cases. Civil twilight lasts until the Sun passes 12 degrees below the horizon which starts nautical twilight.
See twilight.
