Dawn

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.

[5] At this point, a very small portion of the Sun's rays illuminate the sky and the fainter stars begin to disappear.

[6] Nautical twilight begins when there is enough light for sailors to distinguish the horizon at sea, but the sky is still too dark to perform outdoor activities.

[6] The duration of the morning twilight (i.e. between astronomical dawn and sunrise) varies greatly depending on the observer's latitude: from a little over 70 minutes at the Equator, to many hours in the polar regions.

[citation needed] The polar circle (at 66°33′50.3″ north or south) is defined as the lowest latitude at which the Sun does not set at the summer solstice.

[citation needed] Around the summer solstice, Glasgow, Scotland at 55°51′ N, and Copenhagen, Denmark at 55°40′ N, get a few hours of "night feeling".

When the Sun gets 9.0 to 9.5 degrees below the horizon (at summer solstice this is at latitudes 57°30′–57°00′), the zenith gets dark even on cloud-free nights (if there is no full moon), and the brightest stars are clearly visible in a large majority of the sky.

[citation needed] In Islam, Zodiacal Light (or "false dawn") is referred to as False Morning (Subhe-Kazeb, Persian صبح کاذب) and Astronomical dawn is called Sahar (سحر) or True Morning (Subhe-Sadeq, Persian صبح صادق), and it is the time of first prayer of the day, and the beginning of the daily fast during Ramadan.

[citation needed] In Judaism, the question of how to calculate dawn (Hebrew Alos/Alot HaShachar, or Alos/Alot) is posed by the Talmud,[11] as it has many ramifications for Jewish law (such as the possible start time for certain daytime commandments, like prayer).