Difference Between Dusk and Dawn (With Table)

Dusk vs Dawn

Twilights are crucial for the Military, Navy and Aviation industry and they often use specific terms such as BMNT and EENT to define and set rules for strategically important decisions. But for the common man the simplest terms dusk and dawn can be confusing.

The difference between dusk and dawn is that dusk is the twilight before Sun sets on the West and dawn is the twilight before the Sun rises on the East horizon.

However, there are three types of twilight based on the angle of the sun on the horizon. These are civil twilight, nautical twilight and astronomical twilight.

Considering this, dusk and dawn have a list of differences that must be noted while making this list. Such as for civil twilight, dusk is when the Sun is 6 degrees below the horizon before sunset in the evening whereas dawn is when the same situation arises in the morning.

In case of nautical twilight, the difference between dusk and dawn is when the geometric centre of the Sun is 12 degrees below the horizon in the evening it is dusk while dawn is the same but in the morning before sunrise.


 

Comparison Table Between Dusk and Dawn

Parameter of ComparisonDuskDawn
By definitionIt is the twilight before sunsetIt is the twilight before sunrise
Civil twilight specificationWhen the Sun is 6 degrees below the horizon before sunriseWhen the Sun is 6 degrees below the horizon before sunset
Nautical twilight specificationWhen the Sun is 12 degrees below the horizon in the eveningWhen the Sun is 12 degrees below the horizon in the morning
Astronomical twilight specificationWhen the Sun is 18 degrees below the horizon in the eveningWhen the sun is 18 degrees below the horizon before sunrise.
Polar twilightPolar dusk, Begins after September equinox and lasts for a few daysPolar dawn, begins a few days before the March equinox

 

What is Dusk?

In general terms dusk is perceived as the twilight before sunset on the western horizon. This is the time that marks the end of the daylight and beginning of the dark hours. This transition phase receives dim sunlight and often the sky is masked with beautiful colors that are formed while the last of the sunrays plays reflection games with the varied particles of the atmospheric layers.

However, there are several technical specifications that define dusk in civil, nautical and astronomical twilight definition.

The civil dusk is when the geographic centre of the sun is 6 degrees below the horizon while the nautical dusk is when the sun is 12 degrees below the horizon.  However, the astronomical dusk finally marks the end of the day. It is when the sun is 18 degrees below the horizon and no sunlight is visible beyond this. The end of astronomical dusk marks the end of the sunset.

Further, dusk is shorter in the tropical and equator region while it is longer as we go towards higher latitudes. A polar dusk remains for the longest time. It begins at the September equinox and stretches for a few days before the sun completely sets for the six months and complete darkness prevails.

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Dusk scaled
 

What is Dawn?

Dawn is the twilight before Sun rises on the Eastern horizon. The sky is generally colored in a light orange and red hue during this time and this marks the beginning of the daylight

The end of dawn is marked by the complete sunrise. However, the phases of a dawn are separated based on the degree of angle of the sun’s geometric center with the horizon. A civil dawn is when the sun’s geometric centre is 6 degrees below the horizon and nautical dawn is when it is 12 degrees below the horizon. Astronomical dawn is when the Sun is 18 degrees below the horizon.

An astronomical dawn marks the beginning of the morning twilight followed by nautical and then civil twilight which ends with complete sunrise. The length of dawn too depends upon the latitude and longitude of the place. Dawn in the equator and tropics are shorter than the ones in higher latitudes.

Dawn prevails for the longest time in the extremes but alas, only once a year. The polar dawn begins a few days before the March equinox and marks the beginning of the daylight days in the poles.

Dawn

Main Differences Between Dusk and Dawn

  • The main difference between dusk and dawn is that dusk is the twilight before Sun sets on the West and dawn is the twilight before the Sun rises on the East horizon
  • Civil dusk is when the Sun is 6 degrees below the horizon before sunset in the evening whereas civil dawn is when the same situation arises in the morning.
  • The difference between nautical dusk and nautical dawn is when the Sun is 12 degrees below the horizon in the evening it is nautical dusk while nautical dawn is the same but in the morning.
  • Astronomical dusk is when the sun is 18 degrees below the horizon in the evening whereas dawn is when it is 18 degrees below the horizon in the morning.
  • A polar dusk begins at the September equinox whereas a polar dawn ends at the March equinox.

 

Conclusion

These measures of dusk and dawn, determining the end and beginning of the day are extensively used by aviation specialists to set guidelines, rules and safety measures while the military uses them for strategic planning.

 In general terms the dusk marks the end of the day while dawn marks the beginning of the day. In more specific terms, an astronomical dusk marks the end of sunset while an astronomical dawn marks the beginning of the sunrise.

However, the main difference is that dusk is the twilight before sunset while dawn is the twilight before sunrise. Furthermore a civil dusk marks the beginning of the sunset while a civil dawn marks the end of the sunrise. A nautical dawn and dusk is the time in between civil and astronomical dusk and dawn respectively.  


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