How Long After Sunset Does It Get Dark?

If you want to do some stargazing, break out that telescope and reveal all that the night sky has to offer, you’ll need to know when it gets dark. Granted, this seems like an obvious question…but is there more to it than that?

Once the sun sets it will obviously get dark, however, by definition when is it actually dark? In this article we’ll explain, how long after sunset does it get dark?

This is why, today, we want to take a look at the question: “How long after sunset does it get dark?” – and answer it every step of the way for you. We think you’ll be surprised to find out the answer to this seemingly simple question.

To answer this question properly, we’ll be going over quite a bit of information. Some sections will be more technical in nature, so just make sure that you check which areas you’re most interested. Here the general outline for this guide:

  • Understanding the different phase of twilight, such as, civil twilight, nautical twilight, and astronomical twilight.
  • Learn the difference between twilight times.
  • Explore how long it takes to get dark after sunset.
  • Review other factors relating to how the sun moves, sun sets, and sun rises.
  • A brief recap and some final thoughts.

Now that you know what we’ll be diving into, let’s jump right in, and take a look at the answer to: how long does it take to get dark after sunset?

Twilight: What does it really mean?

Image showing phases of twilight such as civil twilight, nautical twilight, and astronomical twilight.

When it comes to twilight, we’re not referring to the famous vampire movie, but instead something entirely different. If you want to get an idea as to how long it takes to get dark after sunset, you’ll need to fully understand twilight as a concept.

What exactly is twilight?

The twilight period is the time period right before it becomes true nighttime outside. This period is brought about by the sun setting, but as it sinks beneath the horizon some light will still be visible.

While it may appear very dark when this occurs, there are actually three different phases of twilight before it there is complete darkness.

So when you think about twilight, think of the period of time between night and day. However, it’s not quite as simple as this, as you’re about to find out…

Image showing the shadow line and when the sun disappears and it gets completely dark.Image source: https://en.wikipedia.org/wiki/Twilight

Before we jump into the facts about each twilight phase, we want to mention some quick guidelines to take into consideration. This is due to the fact that it’s possible to stargaze during the twilight hour, however, you won’t be able to see the full scope of the night sky. The sun will add a different level of light pollution at each phase of twilight, so let’s discuss each.

Civil Twilight

This is the first phase or twilight, and while it may seem dark, true darkness is actually further off than you may think. This is due to the fact that during Civil Twilight some light from the sun remains.

This means that you might want to hold off on stargazing during this period of twilight. Here are some quick things to understand about Civil Twilight:

  • This phase occurs when the sun first sets, and this phase ends when it reaches 6° beneath the horizon.
  • From this phase you’ll likely see bright objects like planets, however, the natural light still present will make anything else hard to view.
  • If you want an easy way to view or track down Venus and Mercury, this is a great time to do it. Fainter stars and planets will not yet be visible during this phase.

Think of Civil Twilight as dusk. It’s not yet true darkness, but the sun is definitely nowhere to be found.

Nautical Twilight

Nautical Twilight occurs right after the Civil Twilight ends, and during this phase things begin to get really dark. Now, obviously things won’t be pitch black quite yet, but you’ll still need some help to see if you’re going to be outside.

The good news about this phase of twilight is that you’ll be able to see the star constellations, and some other higher magnitude celestial objects.

Here are some quick things to understand about Nautical Twilight:

  • This occurs once the sun has reached 6° below the horizon, and continues until the sun reaches 12 degrees below the horizon.
  • You’ll be able to start stargazing.
  • Shades of color will be much harder to distinguish.
  • The night sky will resemble a dark blue color.

If it seems like it’s pitch black, but the sky resembles a dark blue color, chances are you’re in the Nautical Twilight. You can begin to stargaze, but keep your telescope away from the horizon for the best experience.

Astronomical Twilight

Astronomical Twilight is the final phase of twilight, and once this phase is complete total darkness will start to occur. While it may not be 100% nighttime, that doesn’t mean that’s it not dark.

Plus, to be blunt, it’s very hard to distinguish between Astronomical Twilight and true night. So if you want to get a head start on some stargazing, feel free to breakout your telescope during this phase.

Here are some things to keep in mind about Astronomical Twilight:

  • This phase begins once the sun dips to 12° below the horizon, and will continue until the sun reaches 18° below the horizon.
  • You’ll be able to see most of the objects in space, including some of the faintest stars.
  • The only bit of light pollution you’ll find is near the horizon.

Once Astronomical Twilight occurs you can really dive into stargazing. Obviously, you should still refrain from looking towards the horizon, but you’ll be able to stargaze as if it was night time otherwise.

How long after sunset does it get dark?Image source: https://en.wikipedia.org/wiki/Twilight

Understanding the phase of twilight you’re in, and what you can see during each phase, is important if you want to get the most out of stargazing. If you want to see the most, and do so without wasting time, we recommend that you wait until the twilight phases are done.

What ‘night time’ actually is?

Now that we’ve touched on the topic of twilight, the next thing we want to focus on is true night time. This is due to the fact that many people believe that once it’s dark it’s night time, but this is actually not the case at all.

Plus, on certain days of the year – like the summer solstice – the amount of true night time is significantly lower. That’s why, in this section, we want to break this down for you.

So what is this “true – or real – night” we’ve been talking about?

We know that we’ve thrown this phrase around quite a bit, and while it may sound complex, to be frank it’s quite simple. Once all of the twilight phases we went over are concluded, we move onto true night.

This is when the sun will have no impact on your viewing capabilities, and there is little to no light pollution coming from the sun except from, perhaps, artificial light sources. Therefore, when push comes to shove, true night is just pure darkness.

You’ll know it’s true night when the sun vanishes and has no influence at the horizon. So if you want to maximize your stargazing experience, we definitely recommend that you go ahead and wait until this time of night to do so.

So how long does it take to get dark after sunset?

Image of the earth's surface with the milky way above the horizon in outer space.

We’ve gone over what true night time is, and we’ve also broken down the concept of twilight. So while the first two sections may have seemed a bit on the dry side, trust us on this one, this is important stuff if you want to maximize your stargazing experience.

Luckily, now that we have the basics taken care of, it’s time to start answering the question.

So how long after sunset does it get dark?

This is a question that actually requires a couple of different answers. This is due to the fact that no place  on Earth is the same, and certain factors impact the outcome.

While this may be true, one thing we do want to state is that we’re talking about “true night” in this section, because the twilight happens over a short period of time. Now that we got that out of the way, the average time for it to get dark in the northern hemisphere is about 65 to 140 minutes.

So while the sun may be out of view, you can see that there is still some waiting to be done.

It all comes down to the equator

If you live in the northern areas of the United States it’s going to take quite a bit of time to get dark. While the individual times by state will vary, if you live near New York or Seattle, you can expect it to take upwards of 100 to 140 minutes for it to become true night.

Now, if you happen to live in equatorial regions such as Florida, the time in which true night comes will be reduced to that 70-90 minute mark.

A great thing to keep in mind is that these times do fluctuate based on your location, but if a good rule of thumb is that you should wait at least an hour to begin stargazing after sunset.

Factors that impact the rate at which it gets dark

Image of when the sun begins to disappear below the horizon.

Finally, before we let you go, there is more to this whole day and night thing. This is due to the fact that there are actually factors that can impact the amount of time it takes to get dark.

So while you may have a clear idea in your head for your area, we want to take some time to show you some other factors you should be keeping an eye on.

Your proximity to the equator

As we mentioned earlier, this is definitely one of the largest factors in regard to how long after sunset it gets dark. This is due to the fact that the Earth is in the shape of a sphere, which means that you’ll still be able to see light coming from below the horizon.

Now, if you’re closer to the equator (the invisible line that spans the middle of the world), you’ll discover that true night will arrive sooner. This is due to the fact that the sun will drop out of view much faster. However, if you live in the north pole the sun only rises once each year.

The seasons

Another factor that contributes to how long it takes to get dark after the sun sets is the season you’re in. This is due to the fact that Earth will actually change positions around the sun as the year goes on, but in most areas the difference is nothing extreme.

For example, if you live on most United States mainland you’ll find that the difference is only a couple of minutes.

This does change the further north you go. In some cases the sun disappears completely and there may be no true night at all during the summer months. This applies to a few of the northern most states, but the place where this is the most notable is Alaska.

In Alaska, at times, there is no true night at all. So if you decide to head to Alaska for stargazing, well, you might want to head up there during the colder months when the aurora borealis is optimal for viewing.

Another good rule of thumb to follow is that if you happen to live near Canada – and we mean like right on the border – you’ll also experience times during the summer where doesn’t get properly dark at all.

While the time in which it takes to get dark is going to remain mostly consistent, certain factors will impact the amount of time it takes. This applies to locations close to the equator (where true night comes much faster), and locations further north where true night may not exist during the summer months.

Final Thoughts

As is usually the case here on AstroJunkies.com, we went into a great amount of detail to explain this phenomena. So how long after sunset does it get dark? The short answer is roughly 70 to 140 minutes.

This is a good rule of thumb to keep in mind when planning your next stargazing outing. However, as we’ve mentioned throughout this article, this can change based on your location. Plus, if you live really close to the equator, it can take as little as 23 minutes.

If you want to stargaze, and you’re serious about getting the most out of the experience, allow 70 to 140 minutes after sunset for the night sky and your eyes to adjust. The concept of true night is something you should know and understand well.

So now that you know the facts, and how long after sunset it takes to get dark, we hope that you can do some serious stargazing.

Let us know what you find out there!