How to Stargaze in Cities – Doing Astronomy Under Streetlights

Backyard astronomy is a hobby shared by millions of enthusiastic amateur astronomers worldwide, but those of us stargazing in urban areas have to fight hard to actually see objects in the night sky.

In the US, 83% of the population now stays in urban areas where light pollution is more common, compared to 64% in the 1900s. Researchers estimate that by 2050, almost 90% of the US population will move to urban areas.

Light pollution shown over Paris
Light pollution over the city of Paris (source)

Similarly, the urban area population has grown in the UK as well; roughly 55.9 million people occupied urban areas as of 2019.

Despite the shift, there are beautiful stargazing experiences possible even in light-polluted areas, so not all is lost. This article will help amateur astronomers make the most of their equipment and location to get the best results.

When to Do Astronomy to Maximize Your Results

Dark skies offer the best stargazing experiences with clear views of many celestial objects. Artificial sources of lighting increase the night sky’s brightness, making it difficult to see deep sky objects

While a suburban sky is 5 to 10 times brighter than a rural one, a sky at the city’s center is 25 to 50 times brighter, making all but the brightest targets impossible to see.

While we can’t control how much artificial light shines on our viewing area, we can take steps to improve our chances for decent astronomy.

Opt for Moonless Nights

A city sky is already polluted with light, which is why amateur astronomers will benefit from planning their observations on moonless nights (unless, of course, you wish to observe the moon’s features).

Waning Gibbous Moon
The moon is the enemy of a dark sky (source)

You can use online almanacs to keep track of new moons, which mark the beginning of lunar cycles or dates around its last quarter, which is when the moon is below the horizon in the evening.

You could also join the Virtual Astronomy Club for all the moon data you could ever need! (Link opens a new tab)

Check the Weather for Cloudless Nights

Cloudless nights are ideal because they offer unobstructed views of the night sky. In cities, the presence of clouds increases brightness by three times than in a rural location. This is because clouds reflect light from artificial sources back towards the ground.

Indeed, one of the measures used in the Bortle Scale of sky darkness is how bright clouds appear at night.

Colder Days Offer Better Views

You might have read that the best time for stargazing and astronomical observations is during winters. Partly that’s because nights are longer, but it’s also because cold air cannot absorb as much moisture as warm air can. 

This means that the haziness we normally see in summer is not as prevalent during winter, giving us backyard astronomers clearer skies and better views.

Late Nights and Early Mornings

There are a few cities like New York that don’t sleep but, in most places, fewer lights are on in the early hours of the morning than there are in the evening.

Of course, fewer lights mean darker skies, so try to make the most of the dark sky while the world sleeps. 

Rainstorms and Brisk Winds are Useful Too

A 2015 research from MIT suggests that during a rainstorm, the water droplets attract suspended aerosols in the atmosphere before falling on the ground. This process is called coagulation and is thought to clear a lot of soot and sulfates from the atmosphere, helping in cleaning the atmosphere.

A windsock blowing in a gail
Stargazing after a windy day is more productive!

So, while you cannot observe much during a heavy cloud cover or while high winds are blowing outside your window, waiting for them to blow over will result in clearer skies. 

Where to go to Maximize Your Views

Before you go anywhere else, you should understand how dark your sky is, and the conditions that lead to ‘good seeing‘ (both links open a new tab, so you won’t lose this page).

When you’ve done that, these are the steps you can take to improve your urban astronomy prospects, especially if heading for a rural area isn’t a viable option.

Find Big Chunks of Sky

You cannot do or see much by peeping outside your window, which is why you’ll need to go as high as possible in your building to gain a sizable chunk of your sky. 

If going to a rooftop is not an option, you can try visiting your local park, which will likely be less light-polluted and more open, so you can simply gaze up into the depths of the night sky without your view being obstructed by high-rise buildings.

Get Direct Sources of Light Pollution Out of Your Way

Cities are abundant with street lights, lamps, building lights, and other sources of artificial light pollution. These are types of direct light that ruin your night vision even before you look up, so work hard to shelter your eyes and astronomy telescope from direct light.

Image of a streetlight at night
Shelter your eyes and equipment from direct sources of light, such as street lamps.

Others have done it before by using two long poles or sticks with blinds draped over them to block out the light. The same goes for building lights that may be on in your neighbor’s houses. 

The higher You Look, the Better Your Views

The atmosphere near the horizon is thicker (called air mass in astronomy), which means light from a celestial object has to pass through more atmospheric layers to reach an observer on the ground and it will thus be less intense.

Focusing your observations higher in the sky will reduce that atmosphere effect and the sky will appear less hazy and darker. In turn, this offers better contrast, making objects easier to see.

Make the Most of Your Local Astronomy Clubs

Astronomy clubs are made up of space enthusiasts that are keen on hands-on astronomical observing.

All 50 states in the US have at least one official astronomy club and countless more hobby groups put together by such enthusiasts who are eager to share their first-hand knowledge and experiences. 

Joining such groups paves the way not only to networking but also enjoyable company during star parties where people essentially gather in a single place with telescopes and binoculars to stargaze together.  

Moreover, most of such astronomy clubs will have booked dark sky locations in your area or will have knowledge of those, so you can make the most of your city location by going to the darkest regions within the city.

Equipment to Beat Light Pollution

We’ve looked at when to time your astronomy to combat light pollution, and where you can carry it out to make your stargazing more effective. Now, we’re taking a look at the equipment you can use to make urban stargazing more rewarding.

Get that bigger scope

Don’t shy away from getting a bigger scope even if you are in a big city — one has little impact on the other. Larger apertures take in more starlight and will always show you more detail than a smaller scope. 

See this year’s best telescopes, no matter what your budget is

That being said, there are two factors that you must keep in mind while considering a larger scope. 

  1. Choose a scope that is easy to set up and store

It wouldn’t make sense to invest in a telescope that is so huge that it takes you hours just to set up and dismantle for storage. 

Choose a telescope that makes this part of the job easier so that you can spend less time tinkering with your scope and more time watching the sky for your favorite targets.

  1. Larger apertures are sensitive to air currents

Professional observatories are placed on top of mountains as much as possible for a very good reason. The higher altitude makes the atmospheric air clearer and much more stable. 

Such air currents are more common and troublesome in cities, where they disperse light in unpredictable directions, resulting in blurry images. The larger apertures are more sensitive to such currents than smaller ones, which means they need better weather conditions than a smaller scope for optimal and focused views.

Opt for Computerized Mounts With Go-to Tracking

They are rotated by a motor and controlled by a computer and are very helpful to cut through the annoying skyglow. They point you exactly where you need to see in the night sky, saving your time and effort.

A great and popular example is the NexStar SE range from Celestron. Read our full review of the NexStar 8SE.

The Celestron NexStar 8SE telescope.
Celestron’s NexStar 8SE sits on a computerized, go-to mount. It is ideal for urban astronomy.

Use a Red Flashlight

If you’ve walked from a sunny, well-lit room into a completely dark one, you’ll know that your eyes take time to adjust to the darkness.

This is because our eyes are super-sensitive to white light and instantly start to see in color when it is around. It then takes a long time, up to 40 minutes, for full night sensitivity to come back when darkness returns.

While stargazing, astronomers use red light because our eyes aren’t so sensitive to it and it doesn’t trigger the fast change back to color vision.

Buy a red LED flashlight for the best results. You can use this to see your equipment and the people around you without ruining your observations.

Let Your Phone’s Screen Be Red as Well

In iPhones and other iOS devices, go to Settings -> General -> Accessibility -> Display Accommodations. In the “Color Filters” option that you will now see, select “Color Tint” and opt for red. You can increase and decrease its intensity.

Even the light from your phone can be enough to ruin your hard-won night vision, so make sure that you take this step to protect yourself.

Study the Night Sky With Binoculars

Binoculars will allow you a wider field to take in the brighter objects in greater detail. Let’s say the limiting magnitude in your city is 3 or 4, which means the faintest objects you can see with the naked eye are of that magnitude. 

A good, solid pair of binoculars will stretch that to 6 or 7, which is the natural limiting magnitude of a naked eye in a dark sky location. That’s a satisfying starting point.

We’ve reviewed some of the best binoculars for urban astronomy (link opens new tab)

Consider Light Pollution Filters 

Light pollution filters darken the background sky so that your celestial targets stand out, and are often used to fight against the destroying effects of light pollution.

These filters come in handy because they cut out specific wavelengths of light pollution that is rampant in cities: the eerie yellow-orange light from street lamps, cyan-green light from atmospheric reflection, and other subtle colors that city buildings throw into the mix.

We’ve reviewed some of the best light pollution filters for astronomy (link opens a new tab)

While helpful to reduce light pollution, these filters cannot be expected to completely fight light pollution because light from a car will still get through them. They are also not effective against LED streetlights because they generate visible light across the spectrum.

Block Out External Light

Just like we blocked out the light from street lamps with two poles and blankets, you can attempt to cut out the external light by placing a long dew cap on your scope. They work well if you are using a Newtonian or a Dobsonian telescope (like this one) whose secondary mirrors are close to daylight. 

You could also try observing from underneath a blanket or hood, or placing yourself in the middle of a tent with no roof as a temporary light shelter. The sky glow itself isn’t limited by this, but these temporary solutions will help to take direct light away from your eyes and telescopes.

Check the Exit Pupil

The exit pupil tells you how much light enters and leaves your instrument. Knowing the number for the exit pupil is important because our human retina can only dilate up to 5 to 7 mm, which is why choosing a scope with the right focal length is crucial. 

When you increase your exit pupil, you increase the contrast as well, which will make the background sky appear darker, allowing for fainter objects to be seen. 

The exit pupil is both the diameter of your scope’s objective lens and the focal length of an eyepiece. A too-large exit pupil has the reverse effect because it reduces contrast, making it harder to see dim objects.

Always make sure to check the exit pupil, it’ll come in more handy than the magnification on its own.

Night sky targetsExit pupil in mm
Star clusters3 to 5
Deep-sky objects 2 to 4
Double stars 0.5 to 2

Techniques to See Through the Haze

Now we’ve considered lots of ways to combat light pollution, what techniques can we use to carry out our best astronomy given that we have to do it under brighter skies?

Allow Time for Your Eyes to Adjust to the Dark

Our eyes need at least 15 to 20 minutes to adjust to the dark, so try not to check your phones or laptops during this time. We mentioned earlier that doing so will set you back by 30 minutes or more, that’s 30 minutes of precious observing time lost.

Take Your Star Charts With You

Always know what objects you are looking for by locating them on your star maps before you begin observing. This way, you will not waste time finding them in dim lights in your observing location.

When you plan to look for objects to see, you will also notice a way to reach them through star-hopping from the brighter objects to the fainter ones.

Brighter Objects are Stepping Stones to Fainter Ones

Learn the brighter objects visible in your local sky, preferably before you start observing so that your stargazing experience will be more efficient.

Learn the Limiting Magnitude of Your Location

The naked eye limiting magnitude is 6 or 7 even in the darkest locations, which means it is even less in cities. The lower limiting magnitude makes it difficult, even impossible to see a few fainter objects, so try to learn what the limit is for your location. There’s no point in trying to locate objects that there might be no hope of seeing. 

Your astronomy software will also tell you how much of the sky you can see during the night, so you can use that knowledge to outline the objects that will be visible. 

What You Can Actually See

You’ve worked so hard to maximize your chances of a productive urban astronomy session. Now the time has come, finally, to peer through your telescope.

While you won’t see these objects that need a dark location, you can expect to see the following:

The Moon

The Moon is accessible to everyone with the naked eye, and a simple pair of binoculars and a small telescope will highlight more detail than you would initially expect. 

A small telescope will show you craters and valleys that cannot be seen with the naked eye.

Planets

The five brightest planetsMercury, Venus, Jupiter, Saturn, and Mars — are visible even from areas that are polluted by light. 

While the other planets are visible relatively easily, Venus and Mercury will be challenging to view because they don’t often rise high enough in the sky to be visible from cities with high-rise buildings.

Larger telescopes will reveal the must-see astronomy targets: Jupiter’s bands, the Galilean moons, surface features of Mars, and the rings of Saturn.

Mars in Spring
Seeing the surface features of Mars is a huge challenge in polluted skies (source)

Stars

One of the challenging sights, but also that’s a lot of fun for amateur astronomers is figuring out whether a point of light is one star or two, i.e. is it a binary star? A decent telescope will help you do this, although you’ll have to work around the city’s haze.

This is one of the best objects to target from a city because stars are a point source of light, so they cut through the brightness with their high contrast.

Deep Sky Objects (DSOs)

By far, deep sky objects are the hardest celestial objects for a city astronomer to find and enjoy. These objects including galaxies and nebulae have low surface brightness that makes them challenging under good conditions. Added light pollution renders many of these objects invisible.

That being said, the brighter clusters can be seen with a small telescope. Other brighter objects like the Orion Nebula and Andromeda Galaxy can be observed. 

Try to view the fainter objects when there are fewer lights to ruin your experience. You can maximize your views by using an OIII filter that allows only oxygen’s emission line to pass through, increasing the contrast and helping you see the fainter nebula. Similar is the case with a narrowband hydrogen-alpha filter that blocks out most of a city’s glow and moonlight.

All in all, amateur astronomers will benefit from narrowing down on brighter but smaller objects because such targets will have higher surface brightness.

In the same vein as stars, you’ll find that star clusters are rewarding objects to track down even from a bright city center. These islands of suns lend themselves well to being picked out from the lower contrast skies.

The Sun

We don’t need dark skies for this one. The Sun is visible from light-polluted cities, and while you shouldn’t look at it with your eyes directly, you can use your equipment (with proper filters, of course), to study its features.

Summary

Most of us live in cities today, and nearly all of us have to compete with light pollution to some degree. However, this need not signal the end of a glorious ‘career’ in backyard stargazing.

Stargazing experiences are beautiful, even for city dwellers. Irrespective of how much light-polluted a city is, it cannot drown out the brighter stars, planets, and DSOs. 

While some of the fainter deep-sky objects are out of reach, amateur astronomers can still enjoy these 111 wonders! Which one would you like to start with?

Also, why not check out The Urban Observing Program from the Astronomical League?

And if all this doesn’t tempt you into city stargazing, you could instead drive to the darkest sky location in your state.


Written by Sharmila Kunthuner

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