Dawn

Dawn is the start of twilight before sunrise, beginning when the center of the disc of the sun is 18 degrees below the horizon of the observer and indirect daylight first starts scattering through the atmosphere. It is distinct from sunrise: dawn is the period of twilight that precedes it, while sunrise is the specific moment the upper edge of the sun breaks the horizon and direct sunlight takes over from the diffused light of dawn. Like the rest of morning twilight, dawn is divided into astronomical (18 degrees), nautical (12 degrees) and civil (6 degrees) stages, each marking a further step in indirect sunlight and visibility as the night gives way to day.