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You know.. at some places of Earth, the night sky looks like this: (right?)Milkway galaxy seen from Earth

However, you might definitely know that, at some other places, the night sky looks like this:Night sky of a city. No stars to be seen

Have you seen any stars from the last one? So, I was wondering, what are exactly the right conditions, such that the night sky will be like in the first image? To be able to see plenty of stars? Evidently needs to have no clouds. But, what else?

It needs thin atmosphere? No city lights? No suspended pollutants? Needs that certain molecules are not there? No light scattering? No light pollution? So, what are the some of the important conditions that has to happen? And why?

Some remarks:

Now, this answer blames on light pollution from cities. However, during a general blackout some time ago, which sizable areas had no light (over 700Km radius), sure, I could see more stars than before, but never such a great sky. So, maybe light pollution has its contribution, but it is the only factor? Besides, this answer itself acknowledges in the end, that this depends on several factors. And so, I guess I wish a more complete answer.


marked as duplicate by Kyle Kanos, stafusa, Qmechanic Dec 27 '17 at 6:04

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  • $\begingroup$ You will never satisfy all your conditions on Earth, as you know, but why not look up the location and conditions (and compromises) for the large observatories in Hawaii, Chile and the Canary Islands. I have to say I kinda think this is an Astronomy SE (and list) question. Not my d/v, btw, but I don't think your top picture is a human eye view $\endgroup$ – user179430 Dec 26 '17 at 23:54
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    $\begingroup$ @Countto10 Hi! You are right. I made a change to count for the most important ones. Aand.. these are very good ideas.. I'll have a look in these observatories.. $\endgroup$ – Physicist137 Dec 27 '17 at 0:08
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    $\begingroup$ Possible duplicate of Why can I never see any stars in the night sky? $\endgroup$ – Kyle Kanos Dec 27 '17 at 0:43
  • $\begingroup$ You mention that the 1st answer to this question (on light pollution) didn't convince you, what about this answer on general advice for star gazing, or this answer that points to the importance of dust, pollen, pollution, etc. in the air? $\endgroup$ – stafusa Dec 27 '17 at 3:31
  • $\begingroup$ A list: (1) Far from a city and from roads. (2) No clouds. (3) Low humidity. (4) No Moon. (5) Time. The flashlight you used to walk to that special spot on a clear moonless night ruined your night vision. You need to wait at least 20 minutes with no lighting whatsoever to see the full glory of the night sky. $\endgroup$ – David Hammen Dec 27 '17 at 9:42

You pretty much hit all the points. This is why Chile and Hawaii make such great locations for telescopes since they have areas that are high up so the atmosphere is thinner and are far from civilisation whish reduces light and atmospheric pollution. Chile especially is very dry due to the Andes mountains which means cloudy nights are very rare.

The reason you want a thin atmosphere and few atmospheric pollutants is because this reduces the amount of radiation that is absorbed and scattered by our atmosphere meaning we can detect more frequencies and with greater accuracy (even with our eyes). However as previously mentioned the perfect conditions don't exist on earth which is why we have space telescopes.

  • $\begingroup$ Both Chile and Hawaii are too high for the perfect view (for humans). The altitude leads to a lack of oxygen getting to the retina, and the 1st thing to go is low-light level vision, so those +8m stars won't be seen. I hear 8000' is the best. $\endgroup$ – JEB Dec 27 '17 at 0:22
  • $\begingroup$ Chile (at least the optical telescopes) isn't high, and you get to see the Magellanic clouds. At Hawaii though you can see more from the hotel base at 8000ft than at the 14500ft summit because of the lack of oxygen $\endgroup$ – Martin Beckett Dec 27 '17 at 4:03

There are a few factors affecting the clarity of the sky:

  1. Clouds

Obviously, they block out the stars.

  1. Surrounding lights

Basically, since the light from the stars is very faint(it comes from really far away). The light from cities, streetlamps, and so on, kind of "washes" it out. While you may not be looking directly at the light source, it is scattered in the atmosphere. This means that, similar to the blue sky during the day time, wherever you look light is coming at your eyes and fainter stars are hidden. That's why, you can only see stars in rural areas these days.


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