Civil twilight is one of the technical divisions of twilight based on the angle of the sun in relation to the horizon and the resulting level of light in the sky. Civil twilight is the lightest (or least dark) of the three—when the sun is between 0 and 6 degrees below the horizon. In general, the term twilight most commonly refers to the period after sunset before total darkness, but it can also refer to the period before sunrise. Civil twilight occurs in both cases—it is the time immediately before sunrise and the time immediately after sunset. The exact timing and length of civil twilight varies by location and the time of year. Two other divisions of twilight are called nautical twilight (when the sun is between 6 and 12 degrees) and astronomical twilight (often between 12 and 18 degrees). These terms are typically used in technical and scientific contexts, including navigation, astronomy, meteorology, and related fields. The term civil twilight is sometimes used more casually to refer to the time shortly after sunset when there is still some light in the sky (regardless of whether it is technically civil twilight). Still, in casual, nontechnical contexts, the term twilight is much more commonly used. Example: In ideal conditions, some stars are bright enough to be observed during civil twilight.
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