Many of us were interested in why stars are not visible in the sky during the day. After all, they don’t disappear anywhere, they don’t move away, but human eye still unable to see them in the light of the sun. Scientists have long figured out this issue, but, nevertheless, many people still have difficulty understanding the reasons for this phenomenon.
Stars and sun
Each star is a ball of gas of impressive size that emits its own light. This is a key difference from planets and satellites: they create light by reflecting the sun's rays on their surface, while stars have their own glow (because they have nothing to reflect the sun's rays with).
This is the main reason why they are not visible during the day. In addition to this, it is worth considering some other nuances:
- The planet has an atmosphere.
In the atmosphere there is a large number of elements. These are carbon dioxide, hydrogen and dozens of other gaseous substances (including water molecules) that cannot be seen with the naked eye.
When the sun's rays pass through the atmosphere, they have a specific color depending on the color wavelength:
- blue, violet and cyan colors (blue sky) have short waves;
- and long ones are red (sunset).
The sun is also a star, but its rays are so bright that they literally outshine the glow of any other stars and even planets. All other objects in space cannot be seen either, since their glow is much weaker than that of the sun.
- During the day, when the Sun illuminates the Earth, the sun's rays are scattered and refracted.
Thus, the stars cannot be seen during the day, even if you move to another point on the planet (due to the scattering of rays in the atmosphere). Also has great importance presence of the mentioned elements in the air:
- does not retain microscopic dust Blue colour from the sun;
- the presence of molecules of a certain gas (for example, red phosphorus) also affects the color scheme.
- With such a wide range of shades available different colors it is literally impossible to see the stars.
The reason for this is the presence of many light sources (which are created by the sun). Therefore, the glow of stars simply does not reach the surface of the planet, and if it does, the scattered rays of the Sun completely neutralize its impact. This is why stars cannot be seen during the day.
On the other hand, people can still see one star in daylight. But only the brightest of all possible – just the Sun.
Why are no other stars visible from behind the Sun?
It's very simple: the Sun is the only star in our solar system. All other stars are located much further, beyond its boundaries. That is why they cannot be seen during the day - they are too far away, and their radiance is interrupted and scattered under the influence of the sun's rays.
The Sun also consists of several layers that distinguish it from other (studied) stars. Yes, it consists of gases, but around it there is a constantly moving atmosphere, which exceeds the diameter of the Sun itself by 3 and even 4 times. This outer atmosphere is only the first layer of many others that make up the Sun.
Taking all this into account, the fact is once again confirmed that the stars cannot be seen during the day because of this “giant”, which, due to its structure, emits such a bright glow that it is impossible to interrupt it with anything.
At the same time, the structure of the human eye also influences:
- at night, under open air, you can spend hours admiring the stars in the sky;
- but even 3 seconds of looking directly at the sun will be enough to radically damage your vision, and 6 seconds to require surgery to restore the structure eyeball.
Thus, it is again confirmed that the Sun is much brighter than other stars. And it also becomes clear that a person cannot use his eyes in such a way as to focus not on the rays of the Sun, but on more distant objects.
Although this will not be enough, because due to the refraction and scattering of light, the remaining stars completely merge with the sky, the rays of the sun and the molecules of substances. Even technology will not be able to see the stars during the day, let alone human vision?
How can you see stars during the day?
Ancient scientists, Aristotle and Pliny, wrote in their works that stars can be seen during the day from a deep well, cave or long chimney. This is a fairly common opinion: someone claims that it is the real truth, and some call such sayings universal stupidity.
A more modern example is Robert Ball, who in 1889 claimed that he was able to see several stars in the daytime sky while standing in a long chimney. He believed that in a dark narrow pipe, the vision of any person becomes much clearer.
And this makes some sense: once you get from the light into a dark room, it is impossible to see anything. But once your eyes get used to the darkness, you can easily distinguish objects in the room.
However, unfortunately, there are no reliable facts that could confirm this theory. But many people hastened to refute it. Here are the most famous of them:
- Alexander Humboldt, at different times in his life, descended into the deepest mines of America and Siberia, but he was unable to discover any stars;
- Leonid Repin (journalist for Komsomolskaya Pravda) descended to the bottom of a 60-meter well in 1978, but looking up he found only a small piece of the daytime sky, of course, without any stars.
As a result, scientists came to the conclusion that ancient naturalists could perceive small specks of dust as stars, which rose upward (due to the observer’s descent) and slowly floated against the background of the visible sky. In a dark mine, well or other dark room sunlight reflects very beautifully on tiny objects. As a result, such a phenomenon could be perceived as stars, although in reality it is not so.
It turns out that there is no way to see the stars during the day? It turns out that there is, but it is impossible to repeat such an experiment in laboratory conditions. That is, it will not be possible to recreate such a situation with human forces and resources - solar eclipse.
The same thing during which the moon comes between the human gaze and the sun. At this moment, it hits the Earth minimal amount light and it becomes unnaturally dark right in the middle of the working day. Due to the fact that sunlight does not reach the planet, the radiance of distant stars will no longer be refracted or scattered, and the stars can be seen during the day.
Are stars visible during the day (video)?
From this video you will learn whether it is possible to see stars during the day, how the human eye works and perceives light, and why only the Sun star is visible in the sky during the day.
It turns out that technically stars can still be seen in daytime. However, this cannot be done in other ways due to the laws of physics and the structure of the human eyeball. The scattering of light and refraction of rays from distant objects in space does not allow them to be seen even through a telescope. Especially when this is interfered with by the radiation of our Sun.
In the vast expanses of the Internet, I somehow came across the following picture.
Of course, this small circle in the middle of the Milky Way is breathtaking and makes you think about many things, from the frailty of existence to the limitless size of the universe, but the question still arises: how true is all this?
Unfortunately, the creators of the image did not indicate the radius of the yellow circle, and judging it by eye is a dubious exercise. However, the authors of Twitter @FakeAstropix asked the same question as me, and claim that this picture is correct for about 99% of the stars visible in the night sky.
Another question is how many stars can you see in the sky without using optics? It is believed that up to 6,000 stars can be observed with the naked eye from the surface of the Earth. But in reality this number will be much less - firstly, in the northern hemisphere we will physically be able to see no more than half of this amount (the same is true for residents of the southern hemisphere), secondly we are talking about ideal conditions observations that are almost impossible to achieve in reality. Just look at the light pollution in the sky. And when it comes to the farthest visible stars, in most cases we need ideal conditions to notice them.
But still, which of the small flickering points in the sky are the farthest from us? Here is the list that I have managed to compile so far (although of course I wouldn’t be at all surprised if I missed a lot of things, so don’t judge too harshly).
Deneb- the brightest star in the constellation Cygnus and the twentieth brightest star in the night sky, with an apparent magnitude of +1.25 (the limit of visibility for the human eye is considered to be +6, maximum +6.5 for people with truly excellent vision). This blue-white supergiant, which is between 1,500 (last estimate) and 2,600 light-years away, means that the Deneb light we see was emitted sometime between the birth of the Roman Republic and the fall of the Western Roman Empire.
Deneb mass more mass our star is about 200 times the Sun, and its luminosity exceeds the solar minimum by 50,000 times. If he were in the place of Sirius, he would sparkle in our sky brighter than the full Moon.
P The swan is painted red
Mu Cephei also known as Herschel's Garnet Star, a red supergiant, possibly the largest star visible to the naked eye. Its luminosity exceeds the solar one from 60,000 to 100,000 times, the radius according to latest estimates may be 1500 times more solar. Mu Cephei is located at a distance of 5500-6000 light years from us. The star is at the end of its life path and will soon (by astronomical standards) turn into a supernova. Its apparent magnitude varies from +3.4 to +5. It is believed to be one of the reddest stars in the northern sky.
Plaskett's Star Located 6,600 light-years from Earth in the constellation Monoceros, it is one of the most massive double star systems in the Milky Way. Star A has a mass of 50 solar masses and a luminosity 220,000 times greater than that of our star. Star B has approximately the same mass, but its luminosity is lower - “only” 120,000 solar. The apparent magnitude of star A is +6.05, which means it can theoretically be seen with the naked eye.
System Eta Carina is located at a distance of 7500 - 8000 light years from us. It consists of two stars, the main one - a bright blue variable, is one of the largest and most unstable stars in our galaxy with a mass of about 150 solar, 30 of which the star has already lost. In the 17th century, Eta Carinae had a fourth magnitude; by 1730 it became one of the brightest in the constellation Carinae, but by 1782 it had again become very faint. Then, in 1820, it began sharp increase brightness of the star and in April 1843 it reached an apparent magnitude of −0.8, becoming for a time the second brightest in the sky after Sirius. After this, the brightness of Eta Carinae rapidly fell, and by 1870 the star became invisible to the naked eye.
However, in 2007, the star's brightness increased again, it reached magnitude +5 and became visible again. The star's current luminosity is estimated to be at least a million solar and it appears to be a prime candidate for being the next supernova in the Milky Way. Some even believe that it has already exploded.
In conclusion, it is worth mentioning that there have been cases in history when people were able to observe much more distant stars. For example, in 1987, a supernova that could be seen with the naked eye erupted in the Large Magellanic Cloud, located 160,000 light-years away. Another thing is that, unlike all the supergiants listed above, it could be observed over a much shorter period of time.
Author Surdin Vladimir Georgievich
Are stars visible during the day?
There is an old and quite widespread belief that during the day you can see stars from a deep well. From time to time this is stated by quite authoritative authors. More than two thousand years ago, the ancient Greek philosopher Aristotle wrote that stars could be visible during the day from a deep cave. Later, the Roman scientist Pliny repeated the same thing, replacing the cave with a well. Many writers mentioned this in their works: remember, in Kipling - “the stars are visible at noon from the bottom of a deep gorge.” And Robert Ball in his book “Star-Land” (Boston, 1889) gives detailed recommendations on how to observe the stars during the day from the bottom of a high chimney, explaining this possibility by the fact that in a dark chimney a person’s vision becomes sharper. So, are stars visible during the day? I confess that until now I have not had the opportunity to go down into a very deep well or climb into a tall pipe.
However, in different times there were inquisitive people trying to discover the “well effect”. The famous German naturalist and traveler Alexander Humboldt, trying to see the stars during the day, descended into the deep mines of Siberia and America, but to no avail. There are some restless heads these days too.
For example, a newspaper journalist TVNZ" Leonid Repin wrote in the issue dated May 24, 1978: "They say that even in broad daylight you can see the stars in the sky if you go down into a deep well. One day I decided to check if this was true, I went down into a sixty-meter well, but I still couldn’t see the stars. Just a small square of dazzling blue sky." Here is another piece of evidence. An experienced amateur astronomer from Springfield (Massachusetts, USA) Richard Sanderson describes his observations in the Skeptical Inquirer magazine (1992, volume 17, p. 74): "How- Then about twenty years ago, when I worked as an intern in the planetarium of the Springfield Science Museum, my colleagues and I began to argue about this ancient belief.
The director of the museum, Frank Korkosh, heard our dispute and proposed to resolve it experimentally. He took us to the basement of the museum, where a tall and narrow chimney began. It had a small door through which we could stick our heads. I remember the feeling of excitement at the prospect of seeing the night luminaries in broad daylight. Looking up along the chimney, I saw a shining circle blue sky against the background of the impenetrable blackness of the stove interior. From the surrounding darkness, the pupils of my eyes dilated, and a piece of sky sparkled even brighter. I immediately realized that with the help of this “device” I would not be able to see the stars during the day. When we got out of the museum basement, Director Korkosh noticed that only one star can be observed during the day in good weather: this is the Sun. So, witnesses claim that stars are not visible from a deep well, as well as from a high chimney, during the day. However, Let’s not rush to conclusions: through some pipes you can still see stars during the day.
IN in this case We are talking about astronomical tubes - telescopes. What's the matter? Why does a “tube with lenses” allow you to see stars during the day, but a simple tube does not?
First of all, let's think about why the stars are not visible during the day? The answer is quite obvious: simply because the daytime sky is bright due to sunlight scattered by the atmosphere. If for some reason this background weakens, for example, a total solar eclipse occurs, then the bright stars and planets will be perfectly visible during the day. They are also clearly visible in open space or from the surface of the Moon, where the sky is completely black and there is no background light. Why does the sunlight scattered in the earth's atmosphere hide the stars from us? After all, their own light does not weaken. To understand this, you need to imagine the mechanism of our vision. As you know, the main lens, the pupil, creates an image on the back wall of the eye surface, covered with a photosensitive layer - the retina, which consists of large number elementary light receivers - cones and rods. They are sensitive to light in different ways, but this is not important for us now, and therefore, for simplicity, we will call them all cones. The important thing is that each cone transmits information to the brain about the flow of light incident on it, and the brain synthesizes from these individual messages (signals) a whole picture of what it saw. The eye is a very complex receiver of information, and in some ways it is similar to a smart electronic device, such as a radio. It has an automatic gain control system that reduces eye sensitivity in bright light and increases it in darkness. It also has a noise reduction system that smoothes out random fluctuations in the light flux, both in time and across the surface of the retina. This system has certain threshold characteristics, so the eye does not notice rapid changes in the image (cinema principle) and small fluctuations in brightness. When we observe a star at night, the flux of light from it per cone, although small, is significantly greater than the flux from the dark sky falling on neighboring cones. Therefore, the brain records this as a significant signal. But during the day, so much light from the sky falls on the cones that a small addition in the form of starlight per one of these elements is not felt and is “written off” as fluctuations. It is quite easy to see that it is the bright background of the sky that hides the stars from us. Here is an experiment on this subject that Yakov Perelman advises to conduct in his “Entertaining Astronomy” (Gostekhizdat, 1949, p. 155): “A simple experiment can clearly clarify the disappearance of stars in the daytime sky. To carry it out in the side wall of a cardboard box They punch several holes arranged like some kind of constellation, and paste a sheet of white paper on the outside. The box is placed in it. dark room and illuminated from the inside: holes illuminated from the inside then clearly appear on the broken wall - these are stars in the night sky. But all you have to do is, without stopping the illumination from within, light a sufficiently bright lamp in the room - and the artificial stars on the piece of paper disappear without a trace: it is “daylight” that extinguishes the stars." A star can become visible against the background of the daytime sky only if the flow of light from it will be comparable to the flux from the sky area, which the pupil projects onto one cone. Note that the angular size of this area is called the resolution of the human eye and is about 1 arc minute.
Of all the star-shaped objects, only Venus is sometimes visible in the daytime sky. Seeing it is not easy: the sky must be perfectly clear, and you need to know approximately where in the sky it is currently located. All other planets and stars have a brightness much weaker than that of Venus, so it is completely impossible to find them without a telescope during the day. However, some astronomers claim that under ideal conditions they were able to observe Jupiter during the day, which is several times fainter than Venus. But here the brightest star No one has yet been able to observe our firmament Sirius during the day from sea level. True, they say that she was seen high in the mountains, against the backdrop of a dark purple sky. What does a telescope do that allows us to easily observe night stars during the day? Obviously, the telescope lens collects significantly more light than the pupil of the eye. But in this sense, the images of the star and the sky are equivalent - when observed through a telescope, the flow of light from them into the eye increases by the same number of times, approximately equal to the ratio lens area to pupil area. In this case, something else is much more important - the telescope improves the resolution of the eye: after all, it increases the angular size of the observed objects. Moreover, the area that is projected onto one cone during observations with the naked eye is projected into several cones at once in a telescope, which means that each of them receives proportionally less light (for example, if a telescope increases the angular diameter of objects by A times, then the observed brightness of the sky decreases by A 2 times). However, the star has a very small angular size, and its light still falls on a single cone. Thus, the light of the star already appears “solid” against the background of the reduced brightness of the sky. And she becomes noticeable. What happens: take a telescope with high magnification and you can view the faintest stars during the day? No, that's not true. The Earth's atmosphere is inhomogeneous, so the image of the star is blurred and has a very definite angular size, although very small. At night, in good weather, high in the mountains it is about 1 arc. sec. And during the day at sea level - at least 2–3 arc. sec. Therefore, the maximum magnification we can use will be determined so that the star is still a point source. It is approximately 30–60 times. There is no point in a stronger magnification: the image of the star will be projected onto several cones at once, and will begin to weaken in the same way as the brightness of the sky. Let's evaluate how faint stars become visible during the day using a telescope. In clear weather, the daytime sky has a brightness of approximately –5 m per square minute of arc, that is, approximately one cone. The magnitude of Venus is about –4 m. Therefore, we will assume that a star becomes visible if its brightness is no more than one magnitude less than the surface brightness of the sky per square minute. Using a telescope with a magnification of, say, 45 times, we will achieve a decrease in the brightness of the sky background compared to the brightness of the star by 452 (about 2000 times), that is, by about 8 m. This means that in the field of view of the telescope, the brightness of the sky will decrease to +3 m per square minute, and thus stars up to +4 m will become available to us. Experience astronomical observations shows that this is indeed the case. We've dealt with the telescope, now let's go back to the well. Can a well reduce the brightness of the sky for an observer inside it so that the stars can be seen from it? In principle, purely geometrically, perhaps, blocking the entire field of view with the exception of a small area, the flux of light from which will be comparable to the flux of light from a star. But for this to happen, the hole must be visible at an angle of less than one minute to an observer sitting at the bottom of the well. With a well diameter of 1 m, its depth should be more than 1/sin1´=3.4 km! In this case, the hole of the well will be visible to the observer only as a bright point, the brightness of which will increase only for a moment if any the star will pass exactly through the zenith. Even if one wishes, it is difficult to consider this procedure as “observation of the starry sky.” ...
Questions related to the visibility of stars are divided into three types:
- why can't you see the stars in the photos?
- why the astronauts did not see the stars at all, including during the flight to the Moon.
- why do astronauts say that they did not see stars on the surface of the moon.
Why can't you see stars in photographs?
On the first question, examples of “daytime photographs with stars” are often given.
Example 1
“NASA posted a beautiful video from the ISS about the types of northern lights.
But they captured not only the aurora, but also the stars and even the stars against the background of the Sun!”
Here the so-called "skeptic" didn't even understand that this is not the Sun, but the Moon, and the photo was taken at night.
"The lie about the impossibility of photographing the Moon and the stars at the same time.
We invite you to look at it and think about it.... These pictures eliminate many myths and misconceptions in the bud.
... however, these photos remove the myths about different exposures and the impossibility of photographing stars and large bodies at the same time.
We emphasize that these photos also destroy the prevailing lie about the incredibly bright, blinding surface of the Moon."
Here also the so-called the skeptic did not bother to read what was captured in the picture: the surface of the Moon was taken “at night” and illuminated only by the light reflected from the Earth.
Questions about photography have been discussed in detail here for a long time:
To see the visibility of the stars in the photographs, just watch many hours of videos and photos from the ISS.
True, for some reason the photographs of the Chinese Lunokhod 2013. For more or less sane people, the question disappeared. Part of the so-called skeptics were divided. Some understood why the stars were not visible in the photographs, others believed that the Chinese lunar rover was also filmed in the pavilion.
Question No. 2.
"Why didn't the astronauts see the stars at all, including during the flight to the Moon."
The wording of the question “why did the astronauts not see the stars at all, including during the flight to the Moon?” contains an incorrect statement. (An example of how a so-called skeptic makes a similar statement, Example 2)
T.N. Skeptics, to confirm that the astronauts did not see stars during the flight, refer, for example, to Armstrong’s interview
In which, literally, Armstrong answers essentially two questions:
"Mr Armstrong I do realize that when you were on the surface of the Moon you had very little time for gazing upwards but could you tell us something about what the sky actually looks like from the Moon? The Sun, the Earth, the stars if any and so on?"
"Mr. Armstrong, I understand that during your stay on the lunar surface, you didn't have much time to look up, but still, can you tell us a little about what the sky looks like when viewed from the moon? And also the Sun, Earth, stars if they are visible there, etc.?”
and Armstrong gives two answers:
"The sky is a deep black when viewed from the Moon, as it is when viewed from cislunar space – the space between the Earth and the Moon. The Earth is the only visible object other than the Sun that can be seen. Although there have been some reports of seeing planets, I myself did not see planets from the surface, but I suspect they might be visible."
"Sky as seen from the moon deep black, the same as that visible from space inside the lunar orbit - i.e. space between the Earth and the Moon. The only object that is visible besides the Sun is the Earth. Although there were also references to the visibility of planets, I myself have not personally seen planets from the surface, but I fully admit that they can be visible."
The first question concerns what the sky looks like from the lunar surface. And the meaning of the answer boils down to the fact that in color it is not much different from the one visible from space - the same black. The second question is about the Sun, Earth, stars - how they are visible, again, from the Moon. It is about them that Armstrong says that only the Sun and Earth are visible from the surface, etc.
Armstrong does not say here that the stars are not visible from space, nor that he allegedly did not observe them during the flight. This schizophrenia is purely a conspiracy theory.
This was the answer to the question of what is visible from the surface of the Moon. This is what Armstrong is talking about. Armstrong speaks about the space between the Earth and the Moon (cislunar space) only when describing the color of the sky when viewed from the lunar surface. And, of course, the astronauts observed the stars from space during the flight.
Direct observation of the stars, recognition of constellations and specific stars was a routine task in flight, when checking the gyroplatform. For this, the astronauts had specially compiled star maps and lists of reference stars.
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https://4.404content.com/1/B4/E2/1316632616841774690/fullsize.jpg
Other testimonies from astronauts and cosmonauts
Viktor Vasilyevich Gorbatko, Major General, pilot-cosmonaut of the USSR:
If you are in Earth orbit on the shadow side of the planet, then an endless majestic starry sky opens before your eyes. The picture is so grandiose - it takes your breath away! And if you look into space from daylight, illuminated by the Sun, the spectacle, I admit, is unattractive. It feels like the whole space is covered in dirty fog. No stars visible, except that some planets are distinguishable...
http://www.balancer.ru/g/p2754439
Leonov
First impression? Sun. According to the instructions, I should have completely closed the filter. But curiosity won: he covered only half of his face. And it was as if an electric welding arc had hit him. The disc is smooth, without rays or halo, but it is impossible to dazzle. Even in a gold-plated filter of 96% density, the brightness is like in Yalta on a summer day.
And the sky is very black and starry. The stars are both below and above. Sunny night!
(memoirs of Alexei Leonov from E.I. Ryabchikov’s book “Star Trek”)
It should be noted here:
For ten years they have been dragging the same thing around different forums. I didn’t see Leonov’s stars. This was composed for a beautiful word by Ryabchikov himself. There are no stars in his report or in the transcription of radio conversations:
“During the process of free swimming, I made observations and carried out experiments in accordance with the flight program. From space, the surface of the Earth, the horizon, and the details of the ship were clearly visible. The parts of the ship located in the shadow were quite well illuminated by the rays of the Sun reflected from the Earth.”
Another example. Eugene Cernan (Apollo 17) recalled that when he went behind the LM and opened the filter, after a while he was able to see several stars. (see, for example, the flight log of the Apollo 11 expedition, comment after moment 103:22:54)
And from the Lunar Module itself, with the help of optics, astronauts observed them. which is described in detail in the same logbook of the first expedition of the moment 103:15:26 - Aldrin describes how he oriented the platform according to the stars Rigel, Capella, Navi)
As for the possibility of seeing stars on the illuminated surface of the Moon: firstly, you need to understand a little about the structure of vision, and secondly, imagine about the illumination of the surface:
Eye adaptation
The dark adaptation curve consists of two fragments: the upper one relates to cones, the lower one to rods. These fragments reflect different stages of adaptation, the speed of which is different. At the beginning of the adaptation period, the threshold decreases sharply and quickly reaches a constant value, which is associated with an increase in the sensitivity of the cones. The general increase in visual sensitivity due to cones is significantly inferior to the increase in sensitivity due to rods, and dark adaptation occurs within 5-10 minutes of being in a dark room. The lower part of the curve describes dark adaptation of rod vision. An increase in the sensitivity of the rods occurs after 20-30 minutes in the dark. This means that after about half an hour of adaptation to darkness, the eye becomes about a thousand times more sensitive than it was at the beginning of adaptation. However, although the increase in sensitivity as a result of dark adaptation usually occurs gradually and takes time to complete this process, even very short exposure to light can interrupt it.
Dark adaptation of the eye is the adaptation of the organ of vision to work in low light conditions. Adaptation of cones is completed within 7 minutes, and of rods within approximately an hour.
If, before studying dark adaptation, you expose the eye to a bright light, for example, ask to look at a brightly lit white surface for 10-20 minutes, then a significant change in the molecules of visual purple will occur in the retina, and the sensitivity of the eye to light will be negligible (light (photo) stress) . After the transition to complete darkness, sensitivity to light will begin to increase very quickly. The ability of the eye to restore sensitivity to light is measured using special devices - Nagel, Dashevsky, Belostotsky - Hoffmann, Hartinger, etc. adaptometers. The maximum sensitivity of the eye to light is achieved within approximately 1-2 hours, increasing 5000-10,000 times compared to the original and more.
http://eyesfor.me/home/anatomy-of-the-eye/retina/light-and-dark-adaptation.html
The human eye is considered light-adapted at brightness levels greater than 100 cd/m². Night vision occurs at brightnesses less than 10−3 cd/m². In the interval between these values, the human eye operates in twilight vision mode.
wikipedia
Assessment of surface illumination and its influence
The average person, in the absence of knowledge of complex hardware, usually does not have enough imagination to imagine how the world works, how exactly they flew to the moon and what needed to be done for this.
One of these misunderstandings is that the surface of the Moon, from horizon to horizon, has the brightness of approximately that of a gray sheet of paper illuminated by a halogen car headlight located at a distance of 20-40 centimeters from the headlight.
This is how they could observe the stars:
Again: stars are visible when there are resources for it suitable conditions observations, and is not visible when such conditions do not exist. And on the surface of the Earth, and on the surface of the Moon, and in space in orbit, and in space at a distance from the Earth and the Moon, stars may or may not be visible, depending on conditions. No one sane (including astronauts) has claimed or claims anything else.
Both in orbit and in the space between the Earth and the Moon, observing the stars can present significant difficulties if direct light from the Sun or reflected light from the Earth, the Moon, and even parts of the ship enters the field of view.
The best observation conditions in orbit are on the night side, in space far from the Earth and the Moon, it is necessary to select the orientation of the ship so that the stars are visible. On Earth, as you should know, stars are visible only on the night side of the planet; on the Moon the situation is similar - to see stars during the day, you need to try hard. All this is completely consistent with all the statements of the astronauts.
More examples.
Jump from the stratosphere in first person, full version
LED flashlight 1000W - 90,000 lm
The video shows a comparison of the brightness of the low-beam headlights and this flashlight, as well as how it illuminates at a distance of tens of meters (an area of hundreds of square meters) in different situations.
Let me remind you that the sun illuminates every two square meters the surface of the Moon, even taking into account the oblique angle of incidence of light of 30 degrees (lunar morning), a flux of 135,000 Lm. That is, approximately the same as this spotlight from a distance of about one meter (taking into account the reflector and the opening angle of the main light flux cone of 60 degrees, which is approximately equal to one steradian).
Comparison of lunar surface illumination and the ability to photograph stars