Why is it not completely dark right after sunset?

Why can Mercury and Venus be observed only during dusk and dawn?

There are actually a few different kinds of twilight, and all of them impact your astronomy and astrophotography needs. If you want to plan accordingly, then let us take a look at how the Sun sets and how darkness takes over the red skies.


For stargazing, darkness is just as important as good optics and a clear sky. And for photographers, a perfect sunset is a vital part of their portfolio or collection. But if you want to make the best use of your time, you must prepare in advance. The reason is that not all twilights are the same and that the skies are not completely dark right after sunset.

Many factors play into this complex process, and that is why the shift between day and night has always been an inspiration for legends, mythologies, and pieces of art.

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

To answer this question, we must first take a look at the different types of “darkness” that you may mean when asking the question.

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When the Sun sets and rises, layers of light and darkness dance and reveal a lot of different shades of color. Which ones are you targeting and which type of twilight are you waiting for?

Twilight is a time period between day and night. Sunlight is still visible, but the Sun is already below the horizon, or it has not emerged yet. Some photographers prefer taking a picture of a setting Sun, while others love a beautiful sunrise.

A morning twilight is called dawn, while an evening twilight is called dusk. Both come in 3 different subcategories.

A side note – there are two periods of the day called golden hour and blue hour. As these “magic hours” are not measured by the exact time, but rather an artistic description of light conditions, we will not address them in detail, but we will mention a few possibilities they offer during the end of the article.


When the Sun is less than 6 degrees below the horizon, we get the first and brightest form of a twilight. Civil dawn happens when the sun is just about to emerge in the morning, while civil dusk is the moment just after the Sun has set, but has not passed 6 degrees below the horizon.


For astronomers, only the brightest objects can be viewed properly during this time, but that might be a good chance to get a clear shot of some objects without any interference. For photographers, it is a perfect time for some snapshots without any artificial light.


The next form of twilight is darker and occurs when the Sun is between 6 and 12 degrees below the horizon. Nautical dawn and nautical dusk are periods of time where a majority of stars are easily seen by the naked eye.

This means that it is already a good time for astronomical viewings. The use of cameras is still possible during this time, but most things will be very dark and blurry. You might, however, use a camera and a telescope for some terrestrial viewing photographs. A telescope can pick up larger amounts of light and you might be able to take a snap of a city during this time.


When the Sun lies at least 12 degrees below the horizon, but not more than 18 degrees, we are almost completely surrounded by darkness – this is known as the astronomical twilight. As the name implies, astronomical dawn and dusk are fantastic for astronomical exploration, but for normal photographers, this period is not really useful unless you are taking pictures of an illuminated city. Of course, astrophotography is a special case.

Astronomical twilight is often indistinguishable from nighttime – the time period in which the Sun is more than 18 degrees below the horizon. This is especially true for areas that suffer from light pollution. While most bright objects are visible during the astronomical twilight, some faint and distant stars can only be observed after astronomical dusk or before astronomical dawn. This is the second reason for the name of these phases. The faintest objects in the sky can only be viewed during the night.


There are 3 different types of twilight and each of them offers a different experience for astronomers and photographers. Telescopes for terrestrial viewing and cameras flourish during the day and the civil twilight but become difficult to use during the nautical and astronomical twilight. One of the only things one will be able to capture during this period are long exposure images. Telescopes for astronomical viewings will function amazingly, but some distant objects can only be viewed during complete darkness during night time.


This essentially means that it takes quite some time after the Sun has set for the outside to become dark. For most intents and purposes the astronomical twilight is already the end of the day, but for the best experience, it has to get even darker. This is another reason why planning ahead is very important. Setting up your telescope, for example, is very difficult during the night. You should either set it up during the day and wait for the night to fall, which means that you will need some food and water beside you, or you can bring an artificial light source like a strong flashlight.


How Long Does it Take To Get Dark After Sunser In My Region?

If we told you that the further north you are, the longer twilight lasts during summer, you would probably not be able to explain exactly why that is the case. The reason is that there are multiple factors that play into the calculations. Because of that, it is difficult to estimate the actual time it gets dark unless you have a lot of experience.

Let us take a look at the different factors.



The Equator is defined as the line drawn around the Earth at the middle between the poles. This line divides Earth into northern and southern hemispheres and thus, it is constituting the parallel of latitude 0°. Latitude is what we call a geographic coordinate. This coordinate specifies the position of a point on the Earth’s surface in terms of north and south.

The distance from the Equator will play a role in how soon the Sun sets. 

Now let us consider something: the Sun does not really rise or sets also. This is actually an illusion because of the round shape of the Earth. 

So, latitude decides the duration of day and night, and thus the duration of twilight. Along with that, it also decides the position of the Sun at noon which, can be anywhere between the top of your head and the horizon.

One rule of thumb is that from the March equinox until the September equinox, the farther north you go, the earlier the sunrises are and the later the sunsets are. This is because the northern hemisphere is tilted toward the Sun during that period.


As you probably know, days get longer during the summer and shorter during the winter. This also means that the twilights last longer during the summer. But things tend to get complicated really quickly, so take your time trying to wrap your head around it.

The December solstice is the time when the Sun reaches the most southerly point in the sky. This results in the longest day of the year in the southern hemisphere. This makes the December solstice the Summer solstice in the south.  For the northern hemisphere, the June solstice is the summer solstice, so the longest day is in June.

One would easily think that the summer solstice should have the earliest sunrise and the latest sunset – it makes sense because that would allow for the longest day easily. But this is not the case in most places.

This strange phenomenon is caused by the combination of the Earth’s tilt of 23.5 degrees and its elliptical orbit.

Many assume that our planet’s changing the distance from the Sun during a year and that that causes the change in the seasons. That is, just like the previous example, very logical, but the truth is different.

When the North hemisphere is experiencing summer, that is because the North is tilted towards the Sun and receives more sunlight than during winter. The opposite is true for the South hemisphere. Earth’s tilt is, however, not completely constant, which makes the calculations for the times of year and twilights even more complicated, but the tilt is mostly aligned with the North Star. 


Altitude obviously makes a difference in Sunset time. Mountains with a bigger elevation are bound to have a later sunset because the horizon is “lower”.

In certain conditions, a “double sunset” is possible. This is a rare phenomenon in areas which have tall mountains nearby. The Sun sets behind a part of the mountain but re-appears behind a different part of the mountain before setting again. 

But in modern times, a different type of double sunset is also possible. The building Burj Khalifa is so tall that you can watch a sunset twice during the same day. If you watch a sunset at the ground, then take the elevator, you will be able to experience a second sunset. The difference is most often around 3 minutes.


Here we will have a table with sunset and twilight times across a few major cities in the world. You will see that during the same day, the sunset time will be drastically different because of the different conditions described before. 

We will provide a table for July and one for January so that you can see how big the differences can actually be during summer and winter. Keep in mind that places in the South hemisphere have the seasons inverted when compared to the northernern hemisphere.  For clarity and precisions, we will use the 24h system (also called military time).



As you can see, there are quite a few peculiarities going on throughout the world. During summer, it can happen that a place does not experience a real night at all. That, of course, does not mean that the outside is bright. The astronomical twilight is, by most standards, complete darkness – it is only in an astronomical sense that it is not totally dark, meaning that some very faint objects are difficult to detect with telescopes.

You can also notice that there are quite big differences in the dawn and dusk times in different seasons. During winter you will have more time to explore the darker phases, making it slightly better for astronomy as long as it is not too cold to operate equipment, while summers are somewhat better suited for cameras and photography. But, of course, each season allows you to take different pictures and explore different objects. And you should not forget the crossover hobbies like terrestrial telescope exploration and astrophotography.

A fun fact – there are no seasons around the equator because the alignment towards Sun stays constant throughout the year! 


To summarize: the exact time of sunset and sunrise are very difficult to calculate without a lot of experience, even when talking about a single city. There are many factors that will impact your hobby. What we recommend is using a website to calculate the exact times.

By finding the correct times of different types of twilight, you will be able to plan accordingly and use your time more efficiently to get the best shots possible or to find the best time to locate certain objects. Depending on your sleep and work schedule, this might be a very important part of your hobby.

Here is a website we have used to find our data on the different twilight times. It will provide you with a visual representation, the exact duration of different types of twilight, as well as with the duration of day and night.


Photography is normally associated with daytime, while astronomy is associated with the night time. The reasons behind this are fairly simple and intuitive.

For photography, you need a lot of light – if there is not enough sunshine, you will have to use different tools to make up for it or you will end up with very dark pictures. For astronomy, a dark sky is just as important as a clear sky.

But, while all of this is true, twilight in all the different forms can be a very productive time of day. Certain colors appear only during twilight and it can also be used for long exposure shots or astrophotography.

Twilight provides both a gently burning orange color, as well as deep-blue illumination. All of these colors are the result of the scattered sunlight, which is being reflected by particles in the atmosphere. This results in diffuse light, which has a lot of application in photography.

During civil twilight, the sky is fairly bright. You will be able to see only some of the brightest space objects in the sky during this time, but because the outside is still very bright, this is a chance to take some unique astrophotography images, terrestrial observation images, and normal photographs. The light during this time is diffused and different shades of colors appear in the sky in the sky. This makes the civil twilight perfect for portrait and landscape photography. During summer, it is also a great time for moon photography, which can be done with the aid of a telescope, as well.

Two of the best astronomical objects to be observed during civil twilight are Mercury and Venus. The reason for this is that you can not observe these two planets during any other time because they are inner planets, which means that their orbits lie between the Sun and Earths orbit. Finding the correct time for observing these is not just a matter of hours, but also a matter of choosing the correct day, so you will have to plan ahead.

Throughout the nautical twilight, most stars will be visible, so the real astronomical fun can begin. In dark areas, for example at sea, one is still able to perceive a residual background glow. Observations of the Moon and bright planets are encouraged and even astrophotographs will turn out fine.

Most deep-sky objects, however, will be blurred out or completely invisible in the glow of the sky, especially in light-polluted areas. The nautical twilight is, depending on your region, a good time for urban and city photography. The dim and diffused light also allows for some long exposure shots that will not even require neutral density filters, which definitely makes life easier. The option of mounting a camera to a telescope and take some terrestrial shots is still available.

Then comes the astronomical twilight – the sky becomes even darker and most star and constellations are visible. Formations like nebulae and galaxies are difficult to observe with the naked eye. While bright and open clusters are observable with a telescope, diffuse objects such as galaxies might still be a little bit to faint.

During astronomical twilight, moonlight takes over from sunlight, so for photography purposes, you will have to take into account moon phases as the Moon will be your main source of light. In terms of astronomy, you are free to take amazing long exposure shots and pictures of isolated objects like planets and the Moon.

For complete darkness, you have to wait for astronomical night time. This is the only time when galaxies are fully visible with a telescope, so taking a wide shot of a galaxy is tricky if you can not afford to be awake for the whole night.

As mentioned earlier, there are also two time periods which are primarely relevant for photographers, but for astronomers, they might be important if you want to get into terrestrial exploration. These are the golden hour and the blue hour. The exact colorations and times of these “magic hours” will greatly depend on light pollution.

The golden hour is the period of time that approximately takes up the time between sunrise or sunset and the brighter half of civil twilight, although this is only a reference point. The color of the sky transitions from red over to orange and ends in yellow, creating different nuances of golden colors along the way. As the nautical twilight approaches, the warm colors continue to paint the clouds and the land red, while the sky turns blue. In water, the two colors clash. The light during this period is mellow and soft, producing weaker shadows, making it perfect for landscape photography, including terrestrial telescope photography.


The second important photography period is the blue hour. Due to the nature of cities, this period of time is amazing for urban photography, as many buildings will have their lights on, including residential buildings. This time coincides mostly with the darker half of civil twilight. As mentioned before, Moon photography is amazing during this time, as well as terrestrial telescope photography.



As you were able to see, calculating the exact time of twilight is very difficult. The reasons for that are the multiple phases of twilight, the difference during the four seasons, latitude and light pollution. Because it is so difficult to calculate it without prior experience, the best way is to check out one of the numerous websites that can do the calculations for you.

A final tip is to consider the amount of light pollution in areas you want to photograph or where you want to set up your telescope. In clear areas with little light pollution (villages, mountains, and deserts) will generally have dawn and dusk that look the same, except for the exact position of stars in the sky. Light polluted cities and areas with a lot of industrial pollution will have different looking twilights because of the activity of people living and working in those areas. These polluted areas, however, can allow you to take some unique shots that would not be possible if the pollution was not there.

Understanding how the sky and the light behave during the transition from night to day is important for both astronomers and photographers. We hope that you were able to get a basic grasp of how these things work together and that you will be able to get better pictures or find your favorite objects in the sky.


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