Dawn

Not to be confused with Sunrise or Morning. For other uses, see Dawn (disambiguation).
Late summer dawn over the Mojave Desert, California
Dawn is sometimes considered the beginning of morning twilight, the period of twilight, or the time of sunrise.

Dawn is the time that marks the beginning of twilight before sunrise. It is recognized by the appearance of indirect sunlight being scattered in Earth's atmosphere, when the centre of the Sun's disc has reached 18° below the observer's horizon.[1] This morning twilight period will last until sunrise (when the Sun's upper limb breaks the horizon), when direct sunlight outshines the diffused light.

Civil, nautical, and astronomical dawn, when defined as the beginning time of the corresponding twilight[2]
  1. ^ "The different types of twilight". timeanddate.com.
  2. ^ Van Flandern, T.; K. Pulkkinen (1980). "Low precision formulae for planetary positions". Astrophysical Journal Supplement Series. 31 (3): 391. Bibcode:1979ApJS...41..391V. doi:10.1086/190623.