Dawn, dusk, sunrise, sunset and twilight




Dawn occurs before sunrise, before the top of the Sun reaches the horizon. Astronomical Dawn is the point at which it becomes possible to detect light in the sky, when the sun is 18° below the horizon. Nautical Dawn occurs at 12° below the horizon, when it becomes possible to see the horizon properly and distinguish some objects. Civil Dawn occurs when the sun is 6° below the horizon and there is enough light for activities to take place without artificial lighting.

Dusk occurs after sunset, once the top of the Sun has passed the horizon. As with dawn there is astronomical dusk, nautical dusk and civil dusk, occurring at 18°, 12° and 6° below the horizon respectively.

Twilight is the name given to the period between dawn and sunrise, or between sunset and dusk, when light is still visible in the sky due to sunlight scattering off the atmosphere. It can also be separated in astronomical, nautical and civil sections by how far below the horizon the Sun is.

dawn-dusk

Sunrise and sunset are the points at which the top edge of the Sun reaches the horizon; the only difference between them is the direction in which the Sun is moving at the time. It actually occurs when the top of the Sun is 0.57° below the horizon due to refraction of the Sun’s light by the atmosphere.

16 thoughts on “Dawn, dusk, sunrise, sunset and twilight

  1. During Civil twilight it is bright enough to carry out normal activities
    During Nautical twiligh there is enough light to distinguish the horizon for navigational purposes
    Durin Astronomical twilight there is too much light in the sky to perform astronomy

  2. Thank you for this explanation. A small debate in my household ensued as to when I could/should eat as one who indicated she was going to fast from periods of dawn to dusk. My partner believed that sunrise and sunset were synonymous with dawn and dusk. Your visual aid was particularly helpful in our discussion.

  3. This was helpful. As I was gazing at the weather it showed when dawn was and when sunrise was, as well as dusk and sunset. They were all at different times, so I didn’t understand. I thought sunrise=dawn and sunset=dusk. This explanation was very helpful.

  4. Thank you.
    A request: what are the definitions of ‘evening’? After sunset; late afternoon; even afternoon from 12 pm?

  5. There is no set definition for evening. I think most people would say from 1700-1800 onwards, but it has nothing to do with the Sun, Moon, etc.

  6. God, it took me forever to find out whether twilight was BEFORE or AFTER sunset. That should be a pretty easy answer, but everyone was just telling me the angle of the sun, as if I can look outside and have any bloody frame of reference for the angle of celestial objects. “Oh, yeah, it’s at 17 degrees right now.”

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