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I know that minimal light pollution is a must for stargazing, and a place which is away from civilization is better.

Does altitude of a place matter for light pollution?

Does it affect the quality of star gazing?

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Lights affect the quality of star gazing by not letting your eyes adjust far enough to see the dimmer stars. –  Timtech Sep 25 '13 at 10:59

3 Answers 3

up vote 7 down vote accepted

A good question, and in the early 2000s John Bortle published a categorization of a variety of conditions, with descriptions for each category. It is the commonly used scale to describe to others the sort of conditions at a location.

Probably one of the more significant factors provided by a dark sky site is: how faint do stars have to be for you not to see them anymore (overwhelmed by light pollution). There are specific stellar regions, each a triangle, and the idea is you could how many stars you can see in the triangle, and you look the number up in a table, and it will tell you the magnitude limit you are perceiving at that site.

Yes, high altitudes also help - less air between you and the stars means better seeing conditions/less atmospheric distortion.

Being able to see more stars IS better for star gazing. Living in a city, I am continually frustrated at the poor skies, and love being in dark sky locations like the International Dark Skies Reserve at Tekapo, New Zealand.

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I should observe that high altitude observatories are usually there to benefit from the thin atmosphere, but they also happen to be far from cities, which is a not really a coincidence - the combination makes a great site. –  Jeremy Sep 25 '13 at 11:46
    
Nice answer. I share your frustration of having poor skies. I too live in a city. Could you provide a link to that table containing the no. of stars? Btw what is it called? –  udiboy1209 Sep 25 '13 at 17:46
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It is called 'determining the limiting magnitude' : project-nightflight.net/limiting_mag.pdf or imo.net/visual/major/observation/lm are examples. –  Jeremy Sep 26 '13 at 11:23

Yes, altitude does play a role. The higher you go, less photons from civilization will reach you, as most of it will be scattered by dust in the air.

Also, as to answer "what qualifies as a good place", as if you are asking for a criterion, a popular one is : "If you can see all the stars of Little Dipper, well that's a 'good' place to observe".

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I've heard all the stars of the Little Dipper, rather than the entire Ursa Minor constellation. –  GreenMatt Sep 26 '13 at 0:50
    
Well, the lines of IAU standard Ursa Minor is Little Dipper only, so yeah! That's what I actually meant. I'll edit it! If I was unclear to you, I may be unclear to many others as well –  Cheeku Sep 26 '13 at 1:53
    
Not a big deal, I have always heard that there's more to the "little bear" than the Little Dipper; didn't know what the IAU had to say about it. –  GreenMatt Sep 26 '13 at 2:03

The other answers have some good points: Lack of light pollution does make for much better skies, and higher elevation does help by eliminating some of the obscuring atmosphere (of course, you need to be careful how high you go and how quickly, as lack of oxygen can cause problems of several sorts).

I'd like to add a couple things:

  • Obviously, obstructions to viewing (mountains, buildings, trees, etc.) can make viewing certain objects difficult, so a lack of obstructions is good. This can be especially true for viewing something near the horizon (such as Mercury).
  • An easily reached location can be useful. While all the other issues make for good viewing, the fact is a perfect observing site is no good to you if you cannot get to it. I live in a badly light polluted area; the closest pristine skies are a couple hours away in driving time. While I do occasionally drive a few hours to get to nice skies, the majority of my observing has been from an unlit sports field on a hill that I can walk to in less than 15 minutes (drive time is about 3 minutes). Yes, the limiting magnitude is usually about 3, but I can still indulge myself for a little while and get to work the next day, something I can't do when I drive to better skies.
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