Open a map with background illumination characteristics. Will we hear the starry song of the sky? Illumination of the sky. Industrial factor

November 27th, 2014 , 01:32 pm

The world's first atlas of artificial sky illumination (full name - "World Atlas of artificial brightness of the night sky at the zenith at sea level") was compiled by Italian and American scientists based on satellite data. By comparing the information received 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 planet's population, more than half of the residents of the USA 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 zodiacal 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, at least somewhat reminiscent of the night sky.

In addition to showing the degree of light pollution in the sky near cities and other populated areas, 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, and Japan are clearly visible. Southwestern Europe, eastern China, northern India, regions of the European part of Russia, and eastern Ukraine “glow” a little weaker. The brightest “spot” in Africa is in its western part, in Nigeria, but this is explained not by human activity, but by flares of burning natural gas.

A strange, intense glow near the Falkland Islands, which is populated more by sheep than people, may also be surprising. According to the compilers of the atlas, the reason lies in active gas and oil production in this area (apparently, associated gas is flared). Similar “lighting” can also be observed in the North Sea, South China Sea and the Persian Gulf.

City sky without light pollution.

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

Time lapse processed by astrophotographer Sergio Garcia Rill

Astrophotographer Sergio Garcia Rill decided to create a simulated version called "Night City Sky".
“I have been photographing the starry sky for several years, which required me to travel out of town to see and photograph it due to light pollution,” 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 to simulate what it would look like without light pollution.”
His videos include the cities of Houston, Dallas, Austin and San Antonio.

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

In this article we will try to talk in some detail about all the factors that negatively affect the quality of the image built by a telescope and some ways to combat these factors.

Illumination of the sky. Industrial factor

The first thing that usually harms astronomical observations and what both amateur astronomers and professionals try so hard to avoid is sky flare. Of course, it most affected astronomy lovers living in major cities. Harmful illumination can be divided into three categories: general illumination of the sky, caused either by artificial illumination of the air by lanterns or natural illumination of the sky, and local illumination.

The general illumination of the sky is made up of light from street lamps, buildings and other components of urban infrastructure. Light scattered in the air artificially increases the brightness of the sky background. Another significant source of light pollution in the atmosphere 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 for observation.

The pictures below show satellite maps of industrial illumination in the Kyiv and Kharkov regions - more illuminated regions are marked with bright colors, and places with dark skies are marked with dark colors.

Natural sky illumination

There is also natural illumination of the sky - at the height of summer, when it is so convenient to carry out astronomical observations, the nights are too short, the morning astronomical twilight begins only before the evening ends. An observer, even in the darkest place, receives no more than an hour of dark time, which is naturally not enough to carry out serious observations. The shortest nights in mid-latitudes occur on the 20th of July. In addition, even in the suburbs, in corners with a fairly dark sky, illumination 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,” during which astronomical twilight does not occur, and civil twilight continues throughout the night. White nights can be observed in areas above approximately 60th latitude. Although “white nights” are truly magical natural phenomena, astronomy lovers living in northern latitudes take vacations during this time. Even after midnight, the sky has a light blue color, as if the Sun was just about to set.

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

Local illumination

You can get rid of this problem by using a simple hood - a short pipe, 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 out of cardboard painted black, 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 obliquely directed rays. This is how you can simply significantly increase the contrast of an image 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 rays scattered on the surfaces of the anterior meniscus or corrector can also significantly reduce the contrast. In addition, the lens hood will serve as excellent protection against dew falling on the optics.

For lovers of deep sky objects, it is also important to protect the eyes from light exposure. After all, fine details in the structure of nebulae can be seen only after the eye has adapted well to the dark. Many observers use black cloth capes or special eyecups to protect their eyes from extraneous light.

Atmospheric turbulence

When observing the Moon, planets and double stars Often it is necessary to use a fairly large magnification, which will be sufficiently effective only if the image quality is good. But the quality of the constructed image may not always depend only on the optics of the telescope. The image may deteriorate greatly, and fine details may be invisible due to the so-called atmospheric turbulence. The essence of this phenomenon is that masses of warm and cold air mix, creating jets and vertical flows of “trembling” air, similar to what happens over a fire or a hot highway surface. This greatly distorts the image.

The jets passing in front of the lens create round 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, locate their observatories on the slopes high mountains, and, in addition, they use adaptive optics. Adaptive optics is a system that carries out qualitative and quantitative measurements of atmospheric disturbances and, based on data obtained and processed by a computer, distorts the surfaces of optical elements in order to adapt to the atmosphere and improve image quality. Surprisingly, some Western companies are already developing similar technologies for amateur astrophotography enthusiasts. Today, 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 a more stable sky. But if this is not possible, it is necessary to exclude at least artificial turbulence. Buildings that heat up during the day and give off their heat during the night can spoil the image much more than any atmospheric currents. You should strive to move away from such heat sources.

Astroclimate

Unusually, observations by an experienced amateur astronomer often begin with a detailed review of the weather forecast and not just the presence or absence of clouds on the night of observation, but detailed analysis satellite maps of cloudiness and the presence of nearby strong cyclones, air humidity, temperature difference between day and night, wind strength and direction. To confidently get the best results your telescope is capable of, you have to take all of these factors into account.

It’s easy to guess that in addition to a 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 thin 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 proportion of clear nights per year in a given region, during which periods the atmosphere is most stable, and at the same time weather forecasts can be recorded. Such information can be very valuable for planning future, especially serial and systematic observations. In addition, it is worth catching moments of sudden weather changes. Sharp gusts of wind, temperature changes, changes in pressure and humidity are what usually bring little joy to astronomy lovers in weather forecasts.

In addition, the image of celestial objects can change greatly during the night. For example, very good conditions for observing planets can be immediately after sunset, when the air has not yet cooled down, or before sunrise, when the air has assumed a fairly stable temperature after the night. Sudden changes in air temperature a few hours after sunset are usually the cause of poor images. Quite good images can often be achieved after midnight.

For a deep sky observer, systematic assessments of atmospheric transparency are important. If transparency is not so important for planets, but the calm 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. Transparency estimates can be made by observing an area of ​​the sky, such as a known star cluster, linked to data in a star atlas, catalog or planetarium program. Accordingly, it is necessary to take into account the maximum stellar magnitude accessible to the telescope. If the faintest star you discover has a magnitude 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 pristinely dark sky above your head.

Pickering scale

The famous observer of the late nineteenth and early twentieth centuries, William Pickering, created a 10-point scale to evaluate the quality of the image of a star given by a telescope under different atmospheric conditions. The scale goes 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 this the image of the star does not become clear, you should not put the telescope in the closet, because during the night the state of the atmosphere may still change, and in the meantime you can devote yourself to the observation of deep-sky objects.

Conclusion

Having understood the basic requirements, the fulfillment of which is necessary for successful observations, a beginner may become confused and conclude that in his conditions, often 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 depend entirely on how much zeal and healthy enthusiasm the observer puts into achieving the goal. Everyone can improve and protect their observation site in order to achieve better results; we will outline some of the recommendations in this regard in the second part of the article “The Art of Visual Observations”.

And now, to conclude the article, let's look at the example of the famous American observer George Alcock (1912-2000). Even as a child, George, being seriously passionate about astronomy, studied the sky with the help of simple binoculars. Interestingly, George Alcock discovered a mass of comets, asteroids and new stars using an ordinary binocular and a star atlas. Being such an experienced observer, even in the most star-populated areas of the Milky Way, George noticed new stars. For his services, Alcock was recognized as a giant of astronomy by amateurs and professionals alike, and became a member of the British Royal Astronomical Society and the New York Academy of Sciences. The example of George Alcock clearly demonstrates 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 couldn't even see the stars due to the abundance of city light, you're not alone.

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

In the United States, the level of light pollution is so high that it is almost 80% of people are unable to see bright stars in the night sky.

In Europe, more than 50% of the population encounters 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 global atlas light pollution to highlight places where people can count on clear starry skies and places where seeing the Milky Way is nearly impossible, such as Italy, South Korea and parts of the United States.

What is light pollution?

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

Scattered light in the lower atmosphere prevents scientists from making 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 cities, city lighting is reflected upward, thereby creating a "light domes".

In addition, artificial sky brightening is enhanced by dust and aerosols.

Light pollution

Some scientists are concerned that there are entire generations of people today who simply haven't seen the Milky Way - our connection to the cosmos that is being lost.

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

The team believes this is the most detailed atlas of its kind to date.

Using equipment from the Suomi NPP weather satellite and examining 20,865 locations around the world, an international team of scientists found that the most high level Light pollution is found in Singapore, Italy and South Korea, with the lowest levels in Canada and Australia.

It also found that people in India and Germany were more likely to see the Milky Way from their homes than those in Saudi Arabia and South Korea.

Why light pollution is dangerous

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

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

* Residents of megacities can see only 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 lightening negatively affects the growth of many plants. Bright light interferes with the orientation of many insects that are accustomed to being nocturnal. Scientists have noticed that each street lamp can lead to the death of 150 insects per day.

* Scientists have also noticed that light pollution influences 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 experience less sound sleep, which in turn leads to fatigue.

Flare maps They allow you to roughly imagine what and where an amateur astronomer can see, taking into account illumination from populated areas, and choose the best place for observations, if you have a car.
The illumination maps shown here were compiled by members of the forum www.starlab.ru. They were compiled on the basis of illumination maps from approximately 1998-2001. The data is outdated, but I have not yet found more detailed ones, divided into zones.

Unfortunately, the files were originally posted on a third-party temporary resource, from which they are slowly disappearing - I posted them here so that they don’t disappear completely. Next to it are the sizes in megabytes. If you have missing light maps that I didn’t have time to save, please send them!

The light map of the Urals does not open in all browsers. It’s better to immediately save this file to yourself and open it on your computer.

These illumination maps are convenient because they not only show the level of illumination, but are also divided into areas by which you can determine what can be expected in a given area.
Designations of colored zones on the given illumination maps:
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 domes of illumination. The Milky Way reveals 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 is difficult to distinguish 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 difficult to distinguish at its zenith. Domes of light all over the horizon. The 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 altitude the sky is gray. Available magnitude up to 5.0-5.5
White (>27.0) [
The ratio of brightness of the natural and illuminated sky is indicated in parentheses.
The magnitude parameter per square arcsecond is indicated in square brackets.
Don't forget that the lighting is stronger now. Therefore, the illumination maps are somewhat outdated and it is necessary to introduce a correction, shifting for the worse.

Newer light maps, but without color division into zones:
Light map of Minsk: Download(280 kb)
Illumination map of St. Petersburg: Download(250 kb)

Light maps are of course useful, but you can’t escape light pollution even if these maps are three times correct... Try using special filters that absorb certain parts of the spectrum of outdoor mercury and sodium lamps.

 or tell your friends: