Many people out there get confused about what dusk actually is. There are a lot of different terms that are thrown around like dusk, dawn, twilight and many more.
It can be difficult to truly know what the difference between them is. So, I’m going to quickly explain to you what time we actually consider to be dusk, and how it’s different to other periods of time in the evening.
What time is considered to be “dusk”?
The answer isn’t restricted to a specific time in the evening, however it depends on the actions of the Sun. Dusk begins when the Sun descends beneath the horizon, and continues until it is around 18° below. This then transcends into night.
So we know that dusk doesn’t actually relate to an exact time, but rather to the Sun’s position in relevance to our view of the horizon. As the Sun dips below the horizon, we enter into what’s called civil twilight. This is the perfect time for astronomical observations, as you’ll be able to see the night sky without having to worry about the sunlight.
But actually, we also have evening civil twilight, astronomical twilight and nautical twilight too, which we consider to be different stages of dusk.
Stages of Dusk
Like there are three different stages of twilight, there are also three different stages of dusk too. These stages immediately follow the different stages of twilight.
So, we start with civil twilight, which is a period of time where we can still see the objects around us clearly and the night is beginning to come in. Civil twilight is defined as the time when the Sun is between 0° and 6° below the horizon.
Civil twilight then procedes into nautical twilight, which is much darker and we can only make out silhouettes of objects around us. This is when the Sun is between 6° and 12° below the horizon. However, between civil twilight and nautical twilight, we actually have civil dusk. This is the point where the Sun is exactly 6° below the horizon, and it only lasts for a second until civil twlight becomes nautical twilight.
And like civil dusk, we also have nautical dusk too. This is the point when the Sun is 12° below the horizon, and marks the time when nautical twilight (between 6° and 12°) moves into astronomical twilight (12° and 18°). So, nautical dusk is defined as the time when the Sun is exactly 12° below the horizon.
However, when many people are referring to just “dusk”, they’re talking about the time after twilight has finished. This is when the Sun is 18° or more below the horizon, which we call astronomical dusk. So when most people say just “dusk”, this is typically the stages that they’re talking about. After dusk is over, we progress straight into night.
What about the stages of dawn?
Many people still get confused about dawn, and how it differs from dusk. Well, the easiest way to explain dawn is that it’s basically dusk in reverse!
We use the same measurements to assess dawn, and they have the same names as dusk does too. We progress from astronomical dawn, into nautical dawn, and then into civil dawn. However, the words for twilight stay the same for both evening and morning.
So the reality is that dawn is pretty much to opposite to dusk, and we can see the Sun rising from below 18° under the horizon, all the way up until it’s clearly in our view and we’re back into the daytime. Dawn therefore comes before Sunrise, and details the time when the Sun actually isn’t visible in our sight, but below the horizon.
Conclusion
Hopefully this has helped you understand what exactly “dusk” is – it isn’t a time, but it’s just a stage of the Sun going down below the horizon and out of view. But there are many different stages of dusk, and they can be referred to as civil dusk, nautical dusk and astronomical dusk.
We also have to take a few other things into account too, like artificial light. This can potentially have an effect on whether it’s completely dark in your vicinity or not, so it may appear different to the naked eye.
