Light map. Zones of artificial illumination of the sky. Why light pollution is dangerous

Electric lighting creates haze in the sky - light pollution that prevents us from seeing the stars.

We owe the bewitching spectacle of the starry sky to the emergence of ideas about the infinity of the Universe and the multiplicity of worlds, the dream of flying to the stars ... It invariably inspires artists, writers and poets. How many verses are dedicated to the Milky Way alone! “There is no moon in sight. The Milky Way is shining... The stars are talking to each other.” - wrote Konstantin Balmont in 1895.

Light pollution map of Russia (colour codes in the following figure)

Color coding for illustrations. The first column shows the ratio of artificial sky brightness to natural. Secondly, the artificial brightness of the sky in mcd/sq.m.

World map of light pollution

US light pollution map

Light pollution map of Europe

G20 countries ranked by population exposed to light pollution (in mcd/sqm).

G20 countries ranked by size of contaminated area

But here's a surprise: American and Italian physicists have found that a third of humanity, including 60% of Europeans and almost 80% of North Americans, cannot currently see the Milky Way. The reason for this is light pollution created at night by artificial lighting of settlements and roads.

Light from artificial light sources, scattered in the atmosphere, leads to an increase in the nighttime brightness of the sky. Those who flew airplanes at night saw huge luminous domes over major cities. However, the sky also glows over free areas, since light at high altitudes can travel very far from the source.

This atlas shows that about 83% of the world's population, including more than 99% of those in the US and Western Europe, live under sky light pollution. The sky is considered polluted when artificial brightness at the zenith exceeds 14 millicandels per square meter (mcd/m2). Note that the brightness of a moonless night sky in clear weather is 200 mcd/sq.m.

The most polluted country in the world is Singapore, where the entire population lives under a sky that is so bright that the eye does not switch to night vision. The proportion of the population living with this level of light pollution is high in Kuwait (98%), Qatar (97%), the United Arab Emirates (93%), Saudi Arabia (83%), South Korea (66%) and Israel (61%) . It is worth noting that this is due to the high compactness of the population in these countries. Almost all residents of San Marino and Malta cannot see the Milky Way.

Chad, the Central African Republic and Madagascar were the least affected by light pollution, with more than three-quarters of their inhabitants living under untouched skies. Large areas of Canada and Australia also retained the darkest skies.

Of the major European countries, Germany was the most unpolluted, while Spain was the most polluted. The night sky has remained intact only in small areas in Scotland, Sweden and Norway. Light nighttime light pollution affects 23% of the area between 75°N and 60°S, 88% of Europe, and almost half of the US, despite the vast open spaces of the American West. Russia has huge areas of unpolluted territory (more than 80%), but more than 90% of its population lives under the illuminated sky.

Skyglow interferes with ground-based optical astronomical observations. The effects of light pollution on humans are still poorly understood. How does the opportunity to contemplate the full-fledged starry sky affect the development of the individual? After all, this is a profound change in the fundamental human experience. As one of the authors of the work noted, there are already entire generations of people in the United States who have never seen the Milky Way.

Light pollution has a significant impact on nature. Artificial light can confuse insects, birds, sea turtles, and other wildlife, putting them in deadly danger.

It may be worth thinking about managing light pollution. You can shield light sources, reduce their brightness, or just turn them off sometimes.

An interactive pollution map and other data can be viewed at

Perhaps it would be correct to note that visual astronomical observations are a real art, the study of which, as a favorite hobby, many dedicate their whole lives. At the same time, a beginner can often be very disappointed with what he sees even with the highest quality and most expensive telescope due to poor observing conditions and little experience. Yes, exactly where you observe and what methods of observation you use can be a fundamental factor that completely influences the results and your impressions of observations.

In this article, we will try to tell in some detail about all the factors that negatively affect the quality of the image built by the telescope and some ways to deal with these factors.

Sky illumination. industrial factor

The first thing that usually harms astronomical observations, and which amateur astronomers and professionals alike try so hard to avoid, is sky glare. To the greatest extent, it touched, of course, astronomy lovers living in large cities. Harmful illumination can be conditionally divided into three categories - this is the general illumination of the sky, due to either artificial illumination of the air with lanterns, or natural illumination of the sky, and local illumination.

The general illumination of the sky is the light from street lamps, buildings and other components of urban infrastructure. The light scattered in the air artificially increases the brightness of the sky background. Another significant source of atmospheric light pollution can be the Moon, especially during the full moon, our natural satellite reflects enough light from the Sun to make a number of interesting nebulae and galaxies inaccessible to observation.

The images below show satellite maps of industrial illumination of the Kyiv and Kharkov regions - bright colors indicate more illuminated regions, and dark colors indicate places with a dark sky.

natural sky light

There is also a natural illumination of the sky - in the midst of summer, when it is so convenient to make astronomical observations, the nights are too short, the morning astronomical twilight already begins only after the evening has ended. An observer, even in the darkest place, gets no more than an hour of dark time, which is naturally not enough for serious observations. The shortest nights in the middle latitudes are on the 20th of July. In addition, even in the suburbs, in corners with a fairly dark sky, light can spread from a seemingly already distant city when a slight fog appears or the air humidity is simply increased.
In the northern regions there are periods when the sky does not darken at all, these are the so-called "white nights", at which time astronomical twilight does not occur, and civil twilight continues all night. White nights can be observed in areas located above approximately the 60th latitude. Although the "white nights" are truly magical phenomena of nature, astronomy lovers living in northern latitudes take vacations during this time. The sky even after midnight has a light blue color, as if the Sun is just about set.

And the most famous phenomenon of natural illumination of the sky is the beautiful northern lights. They occur near the north pole due to the entry into the Earth's atmosphere and the subsequent ionization of charged particles of the solar wind. The phenomenon is incredibly beautiful, but even at this time it is impossible to conduct any serious observations of deep-sky objects. But on such nights, even the most avid lovers of visual observations take out their cameras to capture this wonderful natural phenomenon.

Local illumination

You can get rid of this problem using a simple hood - a short tube, the length of which is equal to one and a half diameter of the main mirror of the telescope. The lens hood can simply be rolled up from black-painted cardboard, a piece of black plastic, or any suitable material. Thus, by artificially increasing the length of the front section of the pipe, we cut off all oblique rays. This is how you can significantly increase the image contrast when observing in conditions of strong local illumination. Such a hood will be no less useful for mirror-lens telescopes of the Maksutov-Cassegrain and Schmidt-Cassegrain systems, since the rays scattered on the surfaces of the front meniscus or corrector can also significantly reduce the contrast. In addition, the hood will serve as an excellent protection against dew falling on the optics.

For lovers of deep-sky objects, it is also important to protect the eyes from glare. After all, it is possible to consider fine details in the structure of nebulae only after the eye has adapted well to the darkness. Many observers use black fabric capes or special eyecups to protect their eyes from stray light.

Atmospheric turbulence

When observing the Moon, planets and binary stars, it is often necessary to use a rather high magnification, which will be quite effective only if the image quality is good. But the quality of the constructed image cannot always depend only on the optics of the telescope. The image can be severely degraded, and fine details can be invisible due to the so-called atmospheric turbulence. The essence of this phenomenon lies in the fact that the masses of warm and cold air mix, creating jets and vertical streams of “trembling” air, just as it happens over a fire or a hot highway surface. This greatly distorts the image.

The jets passing in front of the lens create rounded and dynamically changing air seals, which act like a poor-quality lens, contributing to a strong loss of sharpness of the telescope. Professional astronomers, in order to avoid this phenomenon, place their observatories on the slopes of high mountains, and, in addition, use adaptive optics. Adaptive optics is a system that conducts qualitative and quantitative measurements of atmospheric disturbances and, based on the data received and processed by a computer, distorts the surfaces of optical elements in order to adjust to the atmosphere and improve image quality. Surprisingly, some of the Western firms are already developing similar technologies for amateur astrophotographers. To date, such devices are imperfect and very expensive, but perhaps after a while everything will change.

Still, now a more affordable option is to search for observation sites with more stable skies. But if this is not possible, it is necessary to exclude at least artificial turbulence. Buildings heated during the day, which give off their heat during the night, can spoil the image much more than any atmospheric currents. It is necessary to strive to move away from such sources of heat.

Astroclimate

Unusually, the observations of an experienced astronomer often begin with a detailed review of the weather forecast and not just the presence or absence of clouds on the night of observations, but a detailed analysis of satellite maps of cloudiness and the presence of nearby strong cyclones, air humidity, temperature differences between day and night, strength and direction wind. In order to confidently get the best result that your telescope is capable of, you have to consider all these factors.

It is easy to guess that in addition to the dark sky, we also need a calm sky. Of course, the ideal would be a clear night somewhere high in the mountains, where the air is very rarefied, and the humidity is low, there is no wind and warm air currents rising nearby ... But, alas, few people have the opportunity to often observe in such conditions. But do not despair, instead, you can study the astroclimate in sufficient detail in an accessible area. Let's say for a year to keep a journal with reports on observations and the quality of the sky, the calmness of the atmosphere and the number of cloudy nights. Ultimately, the observer will receive information about the number and ratio of clear nights per year in a given region, during which periods the atmosphere is most stable, along with this, weather forecasts can be recorded. Such information can be very valuable for planning future, especially serial and systematic observations. In addition, it is worth capturing the moments of a sharp change in the weather. Sudden gusts of wind, temperature changes, changes in pressure and humidity are what usually do not please astronomy lovers in the weather forecast.

In addition, the image of celestial objects can vary greatly during the night. Here, for example, very good conditions for observing planets can be immediately after sunset, when the air has not had time to cool yet, or before sunrise, when the air has taken on a fairly stable temperature after night. Sudden changes in air temperature, a few hours after sunset, are usually the cause of poor images. Often a fairly good image can be achieved after midnight.

For a deep sky observer, systematic estimates of atmospheric transparency are of no small importance. If transparency is not so important for the planets, but the calmness and stability of the image is more important, then a slight haze in the sky will take away a good half of the catalog of deep-sky objects from you. Transparency estimates can be made by observing a section of the sky, such as a known star cluster, by linking to data in a star atlas, catalog, or planetarium program. Accordingly, in this case, it is necessary to take into account the maximum magnitude available to the telescope. If the dimmest star you have discovered has a magnitude that is close to or even equal to the calculated maximum magnitude of the telescope, then you can be sure that you have a beautiful, transparent and primordial dark sky above your head.

Pickering scale

The well-known observer of the late nineteenth and early twentieth centuries, William Pickering, created a 10-point scale for assessing the quality of the image of a star given by a telescope under different conditions of the atmosphere. The scale grows from one to ten and from the worst state of the atmosphere to the best (see animation). Guided by this, you can determine for yourself the calmness of the atmosphere above your observation platform. But you need to remember that in order to get a calm image, you must first let the telescope optics cool down and accept the air temperature. And if even after that the image of the star did not become clear, you should not turn the telescope into a closet, because during the night the state of the atmosphere can still change, and in the meantime you can devote yourself to a panoramic observation of deep-sky objects.

Conclusion

Having understood the basic requirements, the fulfillment of which is necessary for successful observations, a beginner can get confused and conclude for himself that in his conditions, often this is a balcony of an apartment in a multi-storey building, it is completely impossible to conduct sufficiently high-quality observations. But this is not at all the case; astronomical observations are entirely dependent on how much diligence and healthy enthusiasm the observer has applied to achieve the goal. It is up to everyone to improve and protect their observation site in order to achieve better results, some of the recommendations in this regard will be presented in the second part of the article "The Art of Visual Observations".

And now, in conclusion of the article, let's consider the example of the famous American observer George Alcock (1912-2000). Even in childhood, George, being seriously fascinated by astronomy, studied the sky with simple binoculars. It is interesting that George Alcock discovered the mass of comets, asteroids and new stars with the help of an ordinary binocular and a star atlas. Being such an experienced observer, even in the most densely populated regions of the Milky Way, George noticed new stars. For his services, Alcock was recognized as a giant of astronomy by both amateurs and professionals, he became a member of the British Royal Astronomical Society and the New York Academy of Sciences. The example of George Alcock clearly shows that mediocre observing conditions and modest equipment are not at all such a serious obstacle to achieving outstanding observational results.

The science

If you've ever tried to see a meteor shower in the night sky, but due to the abundance of city light, you couldn't even see the stars, you know you're not alone.

Experts have found that due to light pollution, every third person on Earth does not have the opportunity to see the amazing glow of the stars that make up the Milky Way.

In the US, light pollution levels are so high that almost 80% of people are unable to see bright stars in the night sky.

In Europe, more than 50% of the population faced with this phenomenon. In addition, it is worth noting that every year the level of light pollution in Europe increases by 6% - 12%.

Scientists have created a global atlas of light pollution to show places where people can expect clear starry skies and places where it is almost impossible to see the Milky Way, such as Italy, South Korea and parts of the US.

What is light pollution?

Light pollution (aka light smog) is an artificial illumination of the night sky by various sources of lighting created by people - street lighting, light from billboards or spotlights.

Scattering light in the lower atmosphere makes it impossible for scientists to make astronomical observations.

As a rule, large cities, as well as large industrial complexes, suffer from light pollution.

Due to the inefficient design of lighting systems in many metropolitan areas, city lighting is reflected upwards, thereby forming over the city "light domes".

In addition, artificial sky lightening enhanced by dust and aerosols.

Light pollution of the environment

Some scientists are concerned that there are generations of people today who have simply not seen the Milky Way, our connection to the cosmos, which is being lost.

Chris Elvidge, a National Oceanic and Atmospheric Administration scientist in Boulder, Colorado, is part of a team that used high-resolution satellite images to measure and create a global atlas of light pollution.

The team of scientists believe that this is the most detailed atlas of its kind so far.

Using equipment from the Suomi NPP weather satellite and surveying 20,865 locations around the world, an international team of scientists found that light pollution is highest in Singapore, Italy and South Korea, and lowest in Canada and Australia.

It also found that residents of India and Germany are more likely to see the Milky Way from their homes than residents of Saudi Arabia and South Korea.

Why light pollution is dangerous

* Too much nighttime lighting means wasted energy and a significant increase in greenhouse gas emissions.

It is worth noting that on average, one lamp for street lighting consumes 400 watts, which means that for 8 hours of operation it consumes 3.2 kilowatt-hours of electricity. Much of this energy is wasted.

* Residents of metropolitan areas can only see the brightest stars, the Moon and one or more planets, including Mercury, Venus, Mars, Jupiter and Saturn. But they cannot see star clusters, nebulae and galaxies.

*Another important factor: bright light does not allow the human eye to properly adapt to the dark. This leads to the fact that modern observatories have to be built far from densely populated areas.

* Artificial clarification negatively affects the growth of many plants. Bright light interferes with the orientation of many insects that are used to being nocturnal. Scientists have noticed that each street lamp per day can lead to the death of 150 insects.

* Scientists have also noticed that light pollution affects the chronobiology of the human body. So far, research in this area is not sufficiently detailed. But experts have found that such pollution can lead to hormonal imbalances. People have less sound sleep, which in turn leads to rapid fatigue.

Flare Maps allow you to roughly imagine what and where an amateur astronomer can see, taking into account the illumination from settlements, and choose the best place for observations if you have a car.
The illumination maps given here were compiled by the participants of the www.starlab.ru forum. They were compiled on the basis of exposure maps around 1998-2001. The data is outdated, but I have not yet found more detailed, with division into zones.

Unfortunately, the original files are posted on a third-party temporary resource, from which they slowly disappear - posted here so that they do not disappear completely. Sizes are given in megabytes. If you have missing flare maps that I didn't have time to save, please send them!

The Ural light map does not open in all browsers. It is better to immediately save this file to yourself and open it on your computer.

These light maps are convenient in that they not only show the level of light, but are also divided into areas by which you can determine what Roughly you can count on in a particular area.
Designations of colored zones on the given exposure maps:
The black (Grey(0.01-0.11) - The light of the milky way casts shadows on light things. The clouds are darker than the sky. There are no light domes. The Milky Way shows almost every detail. Available magnitude up to 7.1-7.5
Blue(0.11-0.33) - Very clear milky way with structure. Illumination domes up to 10-15 degrees in height. Available magnitude up to 6.6-7.0
Green(0.33-1.0) - Zodiacal light can be seen on good nights. The Milky Way is also visible on the horizon. Available magnitude up to 6.2-6.5
Yellow(1.0-3.0) - The Milky Way is clearly visible at the zenith, but hardly distinguishable towards the horizon. Illumination domes up to 45 degrees in height. Available magnitude up to 5.9-6.2
Orange(3.0-9.0) - The Milky Way is barely visible at the zenith. Domes of illumination all over the horizon. Clouds are brighter than the sky. Available magnitude up to 5.6-5.9
Red(9.0-27.0) - The Milky Way is not available. Above 35 degrees the sky is grey. Available magnitude up to 5.0-5.5
White (>27.0) [
In parentheses, the ratio of the brightness of the natural sky and the overexposed sky is indicated.
The magnitude parameter per square second of arc is given in square brackets.
Do not forget that now the lighting has become stronger. Therefore, the exposure maps are somewhat outdated and a correction needs to be introduced, shifting for the worse.

Newer blowout maps, but without color zoning:
Map of illumination of Minsk: Download (280 kb)
Illumination map of St. Petersburg: Download (250 kb)

Exposure maps are certainly useful, but you can't get away from light pollution if these maps are three times correct ... Try using special filters that absorb certain parts of the spectrum of mercury and sodium street lamps.

 or tell your friends:

November 27th, 2014 01:32 am

The world's first atlas of artificial sky glare (full name - "World Atlas of artificial brightness of the night sky at the zenith at sea level") was compiled by Italian and American scientists on the basis of satellite data. By comparing the information obtained with data on population density, they were able to divide all the inhabitants of the planet into groups depending on the artificial illumination of the sky in their place of residence. It turned out that a fifth of the world's population, more than half of the inhabitants of the US and the EU, respectively, as well as just over 40% of the population of Russia, are deprived of the opportunity to see the Milky Way, the zodiac light and most of the constellations with the naked eye in their place of residence. And finally, a tenth of the inhabitants of the Earth and 1/7 of the inhabitants of Europe and Russia are deprived of the opportunity to see the sky, in any way resembling the night sky.

In addition to showing the degree of sky glare near cities and other settlements, this map accurately reflects the economic situation and population distribution in different parts of the world. Central and northern Europe, the east coast of the USA, Japan are clearly visible. A little weaker "shines" southwestern Europe, eastern China, northern India, regions of the European part of Russia, eastern Ukraine. The brightest "spot" in Africa is located in its western part, in Nigeria, but this is due not to human activity, but to torches of burning natural gas.

Surprise can also cause a strange strong glow near the Falkland Islands, inhabited more by sheep than by people. According to the compilers of the atlas, the reason lies in the active gas and oil production in the area (apparently, associated gas is flared). A similar "flare" can also be observed in the North Sea, the South China Sea and the Persian Gulf.

City sky without light pollution.

This is what the sky of cities would look like if stars were visible in it.

Timelapse edited by astrophotographer Sergio Garcia Rill

Astrophotographer Sergio Garcia Rill decided to create a simulated version called Night City Sky.
"I've been shooting the starry sky for several years, and because of the light pollution, I had to travel out of the city to see and photograph it," Riehl writes on his website. "But I wanted to take a combination of shots where the sky could be seen within the city and did my best to try and mimic what it would look like without light pollution."
His videos include the cities of Houston, Dallas, Austin, and San Antonio.