As you get into stargazing, you’ll quickly notice that all the very best spots are in unpractically remote places. Think deserts, mountaintops, and far-flung islands, for instance.
And that’s no coincidence. These places are great for observation precisely because they’re far from the light pollution of densely populated areas.
But seeing as most of us can’t jet off to the nearest observatory, it’s important to understand the nature of light pollution and how we can cope with it in our own, local surroundings.
Just what is light pollution, anyway?
You’ve probably noticed that stargazing and home astronomy aren’t as simple as meets the eye.
And light pollution is often one of the biggest frustrations when you seek out familiar sights for the first time.
But what is it, exactly?
Light pollution refers to the glow of excessive artificial light that humans produce. It’s not called “pollution” in the ecological sense, but because it undermines natural nighttime visibility. It’s a particular problem for stargazing because the ambient brightness drowns out faint, remote celestial objects and also desensitizes our eyes to the darkness.
The amount of light pollution in your particular area will directly affect which stars and other objects (and how many of them) you can actually distinguish at night.
As you’d expect, light pollution tends to be worst in densely populated areas. In fact, night-sky viewing is nearly impossible in very large cities with dozens of square miles of heavily illuminated buildings and streets.
Certain studies show that not more than a few percent of the overall population can actually have access to a completely dark sky. Hence, light pollution is definitely a problem — but how big of a problem is it?
How much ambient light is a problem?
It should be noted that there are many different kinds of artificial light; all of which fall under the umbrella of light pollution. However, not every kind of light out there is equally problematic in terms of light pollution for astronomy. For instance, the biggest issue is the light emanated directly into your eyepiece or your naked eye from lightbulbs. We call this type of light “glare” — in terms of astronomy, usually emanating from improperly positioned or designed light fixtures.
Now, this is definitely one of the easier problems to deal with as an astronomer — you simply need to position your telescope in the appropriate place; often a shadow-filled corner. Or, alternatively, you could safeguard your telescope from glare with a tarpaulin.
As you might imagine, this type of light pollution is generally something that ranges on a case-by-case basis. However, skyglow is what most people think about when they refer to light pollution in general. This is the other piece of that puzzle; in other words, the light that increases the lighting of the sky. Now, you should know that even when you’re looking at a completely unspoiled night sky by artificial light; it still has some of its own background light, which is natural.
This type of natural skyglow comes to us from all kinds of sources — ranging from distant starlight to the airglow that’s situated in the Earth’s upper atmosphere. All of these factors differ depending on a variety of conditions, but we know their average. And that allows us to measure how much light a naturally lit dark sky should contain, as opposed to the sky illuminated by artificial human light. The consensus is that an average suburban sky is brighter up to ten times compared to a naturally lit sky.
How to find dark skies nearby
Now that we’ve established just how much light pollution can mess up a stargazing session — the question is, how do you avoid it? Luckily, finding places that are not as problematic in terms of light pollution are far easier to find these days than ever before.
Today, there are websites dedicated to finding “dark sites” — in other words, places with minimal light pollution. Regardless of where you live, you can easily pinpoint the nearest site from your location. Now, depending on your location, these might not always be easy to find — but searching for one is still a good idea.
What to do if you can’t get away from light pollution
Of course, at the end of the day — you may simply not be able to get away from light pollution. Going to the nearest dark site could be impractical or too expensive on a regular basis; so what can you do in your current predicament? Well, luckily — there are still some things that you can do to minimize the disturbance from light pollution; though it’s pretty much impossible to eliminate it entirely.
The simplest one is being patient with eye adjustment. As you might already know, the human eyes are capable of adjusting to all kinds of light environments. With that in mind, you’ll find that having some patience with your initial observations in light-polluted conditions will provide you with a better sight later on. If you just walk outside and start peering at the polluted sky, you won’t see much of anything right away. However, give yourself a half an hour — and more and more stars will start appearing!
Apart from this, you also need to be realistic with your observation targets. Naturally, celestial objects that are quite faint and dim will not be as visible in conditions with a lot of light pollution. However, the Milky Way itself is visible quite often. And individual planets of our solar system can actually be spotted even in bigger cities — such as Mars, Venus, Saturn, and Jupiter.
Also, you need to make the best of your position. A general rule of thumb is that the lower you are, the bigger the impact of light pollution will be. In other words, you need to try to elevate yourself as much as possible to minimize its effects. If you can stay safe, being on top of higher buildings always renders a better vantage point.
We also recommend being mindful of the Moon. When you specifically want to see Luna, its light is definitely a welcome sight. But if you want to see anything else, especially in the deep sky — it can be an incredible distraction. Considering this, go to a stargazing website and find a dark sky calendar to ensure that the moonlight does not interfere with your astronomy. Otherwise, you will see that moonlight can be as distracting as any man-made source of artificial light.
At the end of the day (all pun intended), it’s clear just how much of a nuisance light pollution can be when it comes to stargazing. However, this is something that experienced astronomers have learned how to contend with over time — developing a variety of techniques and tools for mitigating light pollution.
Still, your best bet when it comes to minimizing this distraction is to try and find the nearest possible dark site. Sure, you won’t be able to rely on it constantly; but it’s still your best ally against artificial light!