How Long Does It Take To Get Dark After Sunset?

The universe is a fascinating thing - we don’t always know why certain things happen or how.

Sometimes, you may look out of the window to see that the sun is setting and then the next minute you look again and it’s completely dark.

In this case, you may be wondering how long exactly does it take to begin getting dark after sunset? You may wonder why it’s only possible to see certain planets during the hours of dusk and dawn.

Today, we’re here to answer those questions.

How Long Does it Take to Get Dark After Sunset?

So, before we dive on in, the short answer is that it can vary depending on where you are. For instance, countries that are located near to the equator may take only around 20 to 30 minutes to get dark. 

On the other hand, the average time that it takes to get dark in most places is roughly 70 minutes - so yes, in most instances you have time to watch the sun go down!

In the United States it probably won’t take an exceptionally long time to get dark after the sun starts setting - you can expect it to take around one or two hours, though this depends on the season.

If you are located more north in the country then it’s going to take longer for the sun to set. For quick reference, a southern state can expect darkness after 70 minutes or so from sunset, while a northern state could expect darkness after roughly 100 minutes, or 1 hour 40 minutes, from sunset. 

Why Does the Sun Usually Set in the West?

You may be wondering why the sun usually tends to set in the west and rise in the east. Well, in short it’s simply a result of how the sun rotates.

The sun will usually spin to the east, so that’s why you will see it set in that location. 

The Twilight Hours

You’ve probably heard of twilight before, but perhaps you aren’t entirely sure what it means. Well, to put it simply, twilight is the time period between when the sun begins to go beneath the horizon and when it gets completely dark.

This is not technically dark, as you can often see light at this point. You can see three different phases of twilight in total before the darkness truly sets in.

Now, light pollution can be a big problem during the twilight hours, so you should wait another hour or so before you whip out that telescope if you want to see some stars. With that being said, read on for the three phases of twilight.

Civil Twilight

The first phase is civil twilight. At this point it is still possible to see around you quite vividly and you don’t need any extra light at this point. If you wanted to do something like read a book then it’s still possible during civil twilight, though you will need to turn a light on pretty soon.

You will also be able to see some of the brightest things in the sky at this point. Mercury and Venus often make appearances during civil twilight. 

To be more technical, civil twilight usually occurs exactly when the sun is fewer than 6 degrees below the horizon. Civil twilight is also a fantastic time to get your camera out if you’re a photographer!

Nautical Twilight

As you can probably imagine, nautical twilight is a little darker than Civil twilight. This phase of darkness will usually occur as the sun is around 6 to 12 degrees beneath the hoizon.

At this stage you can see the vast majority of stars in the sky, so it’s time to grab your picnic blanket with a loved one and start stargazing! 

Now the light has begun to fade, and it can be significantly harder to tell one object from another. Objects look a little like shadows, and if you’re working outdoors then you may need to invest in a torch at this point.

You may also see that the sky is dark blue at this point, and it will be black in the opposite direction to where the sun has set. 

Astronomical Twilight

The last phase of twilight before it gets dark is astronomical twilight. At this phase, the sun is lying at roughly 12 degrees below the horizon. By the time it hits 18 degrees, the darkness will arrive. 

During astronomical twilight it’s almost completely dark. This is an incredible time for exploring the horizons and seeing the night sky. With that being said, it’s pretty much a photographer’s worst nightmare unless you’re an astrophotographer. 

Now, while it’s pretty dark during astronomical twilight, it is still possible to tell the difference between it and total darkness. If your area has a lot of light pollution then this is even more true.

You can usually see a lot of bright objects in the astronomical twilight, but it’s often only possible to see some of the brightest stars once astronomical twilight has finished.

Conclusion

So, to put it simply, there is no one true answer to how long it takes to get dark. Darkness is a subjective thing - you may think that the civil twilight is incredibly dark when really it’s only the beginning of the twilight.

Either way, if you’re living in the United States then the chances are that it will likely take between 70 to 100 minutes, but this is not always the case.

If you are wondering when it gets dark so you can study some astronomy or do some stargazing, then you don’t need to wait for it to get totally dark to do so. 

In fact, if you look hard enough then you may even see some completely new things if you’re stargazing during the twilight hours that you may not have seen if you had waited for it to get completely dark.

So, the next time that you want to go stargazing, set up a blanket and wait outside as the twilight hours come and go, you may be pleasantly surprised!