Exploring the Earth and Sky of the West

Posts tagged “light pollution

Does the Milky Way Really Look Like That?

The Milky Way is visible in the night sky over a smoke filled lake.
The Milky Way stretches from horizon to horizon with some clouds hovering near the horizon.

The summer Milky Way from Cedar Breaks National Monument in southern Utah.

Capturing stunning images of the night sky has become much easier in recent years. The low-light performance of modern cameras (and even my six-year old Nikon D750) far outpaces the capabilities of cameras made even a decade ago. Recently, I was flipping through some old astronomy magazines from the early 2000s and was shocked not only by the (low) quality of the wide-field astrophotography of the day, but also by the incredibly expensive gear used to produce those images at the time. 20 years ago, it was extremely difficult to capture a detailed image of the Milky Way without a high-end camera and an expensive tracking mount.

Today, even some phone cameras can capture passable images of the Milky Way. Stunning panoramas of our galaxy stretching from horizon to horizon are now a dime a dozen on social media. Given the advanced abilities of today’s cameras, it is natural to wonder: “Does the Milky Way really look like that?” Do the spectacular Milky Way images we see plastered across the internet accurately represent what the human eye can see? Or is this incredibly rich detail only visible to a high-tech camera sensor? Or, more nefariously, could these images simply be the result of some Photoshop trickery? The answer, perhaps not surprisingly, is a combination of all three!

Let’s begin by discussing one way in which most Milky Way images are not representative of what the human eye would see: color. The Milky Way will always look monochromatic to the naked eye. However, the reason why has to do more with the physiology of the human eye than any deception on the part of the photographer. Let me explain.

Some photographers do like to crank up the saturation of their Milky Way images beyond belief. Night sky photos with vibrant blues, purples, oranges, and pinks are the tell tale signs of digital embellishment. Rather than point fingers, I’ve created my own version below to illustrate:

A photograph of the Milky Way with extremely vibrant colors

An image of the Milky Way (and a meteor) over Mt. Adams in Washington state…with the saturation slider cranked up to 100 in Adobe Lightroom.

To be clear, these colors aren’t real. This is Photoshop trickery, pure and simple. Here’s what the same image looks like without the saturation increase:

A photograph of the Milky Way galaxy hovering over a tall volcanic peak.

The same image, with natural color.

Much more subdued, certainly, but look closely and you’ll see that there is still some color there! Here’s the good news: those colors ARE real! Notice the pale green sky behind Mt. Adams. That’s airglow, a phenomenon caused by gas molecules in our atmosphere re-emitting energy they absorbed during the day in the form of ultraviolet radiation from the Sun. If you open the photo full screen and look really closely, you can also see some small pink-ish blotches along the plane of the Milky Way. These are hydrogen gas clouds—stellar nurseries if you will—glowing with the characteristic ruddy hue of ionized hydrogen.

Now for the bad news: while these subtle colors are “real”, you’ll never actually see them with the naked eye. Why not? To sum it up, our eyes suck at seeing colors at night. We see using two different sets of cells in our retinas: rods and cones. The cones are what allow us to see color. Unfortunately, the cones only work when there is lots of light entering our eyes, like during the day. Our rods are mostly responsible for our night vision and they are, sadly, colorblind. This is why the night sky (and low light scenes in general), always appear in shades of gray. Only a few of the brightest stars and planets emit enough light to trigger our color-seeing cones. The diffuse glow of the Milky Way does not.

Cameras on the other hand don’t have rods and cones. They are much better at picking up color in low light, so they naturally produce images that are more vibrant than what we actually experience…no editing necessary!

With this in mind, let’s remove the color entirely from our Milky Way image:

A photograph of the Milky Way galaxy with all color removed

Our Milky Way image converted to black and white, a more accurate approximation of what the human eye sees at night.

With the color out of the picture, is this now what the Milky Way actually looks like to the naked eye? Yes…under certain circumstances.

Look closely at the Milky Way in the image above. Notice the detail. It’s complex. It’s interesting. Some parts are brighter, others fuzzier, with dark blotches and voids winding sinuously from upper left to lower right. The Milky Way is a complex place, and this manifests itself in our view of it from Earth. In this regard, this photo actually does a pretty good job of depicting what the Milky Way actually looks like. You CAN see this detail and complexity with your own eyes…provided that a few things are true:

#1: You have a dark sky. For most people, light pollution prevents the Milky Way from being seen in its full glory. If you want to see the kind of detail shown in a photo like this one, you need to be somewhere dark. Not “turn off the porch light” dark. Not “drive out to the edge of town” dark. Not even “drive an hour up into the mountains” dark. Light pollution is incredibly pervasive and the view of the Milky Way can be degraded for literally hundreds of miles from a major city. Even some of the most remote wilderness areas in the United States are still awash in the glow of artificial light. Places like eastern Oregon, central Idaho, northern Nevada, and southern Utah are among the few locales where you can still experience a pristine night sky. A view of the Milky Way from anywhere else simply doesn’t compare.

#2: Your eyes are dark adapted. Remember the rods from earlier? While our rods allow us to see fairly well in low light, they need at least 20-30 minutes of darkness in order to reach peak sensitivity. This period is known as “dark adaptation” and it is a key ingredient of a successful stargazing session. Gazing at the Milky Way before your rods have had time to fully dark adapt is like looking at a Van Gogh or Monet with dark sunglasses on; you miss many of the finest details. If you walk out of a brightly lit RV or tent and look skyward expecting to see the Milky Way like it appears in a photo, you’ll be quite disappointed. Even using a headlamp or checking the time on your phone while waiting for your eyes to dark adapt can inhibit the process. For this reason, astronomers typically use red lights at night because our rods are less sensitive to that color, making it easier to preserve night vision.

#3: You are in the right place at the right time. We live in the suburbs of the Milky Way galaxy. When we look toward the center of the Milky Way (downtown), it looks brighter, because we are looking at a greater concentration of stars, gas, and dust. When we look away from the center, it looks dimmer. Images like the one I’ve been using in this post are taken looking downtown…toward the galactic center. This portion of the Milky Way is only visible during certain times of year. In late fall, it’s behind the Sun, making it rather difficult to photograph or see. Late evening in the summer and early fall, or early morning in the Spring is the ideal time to catch it. At other times of year, when the galactic outskirts grace our sky, the Milky Way is much more ho-hum. You’ll also want to avoid the Moon, whose glow will mostly overwhelm the diffuse and relatively faint Milky Way.

If all three of these things are true, then yes, the black and white image above is a good representation of what the Milky Way looks like to the naked eye. Sadly, only about 20% of North Americans can even see the Milky Way from their homes, much less see it under ideal circumstances. Light pollution has masked the view of our home galaxy to the point that most of us no longer know what it should look like. Ecologists call this “shifting baseline syndrome”, a phenomenon in which each successive generation comes to regard the state of the environment around them as “normal”. In other words, as we degrade our environment, we gradually forget what things used to be like, or, in this case, look like.

While increasingly rare, such a view of the Milky Way is one of the most spectacular sights in the natural world. I vividly remember a backpacking trip I took over a decade in Aoraki/Mt. Cook National Park in New Zealand. The Milky Way appeared so bright that it cast shadows on the ground, and I was able to read a book (albeit barely…) by its light. Oddly enough, sometimes the “darkest” skies are actually the brightest because so many stars are visible.

Fortunately, light pollution is an easy problem to fix. Many outdoor light fixtures are poorly designed and allow light to escape upward into the night sky. While our modern lives certainly require light at night, that light is almost always needed on the ground, not up in the sky. Illuminating the sky or the crown of a tree makes no one safer or more secure from hazards real or imagined. Light fixtures that direct light downwards (known as “fully shielded” fixtures) eliminate much of the problem. Cities that use such lights, like Flagstaff, Arizona (where I grew up), produce substantially less light pollution than other cities of comparable population. You can see the summer Milky Way from downtown Flagstaff…a city of nearly 100,000 people. Simple actions can go a long ways toward preserving the view of the Milky Way for future generations. (For more on what you can do to combat light pollution, check out the great work being done by the fine folks over at the International Dark Sky Association.)

The Milky Way is visible in the night sky over a smoke filled lake.

A view of the Milky Way over Crater Lake in southern Oregon. A layer of smoke from the 2020 Oregon & California wildfires is seen near the horizon.


Photographing the Night Sky from Colorado

Colorado is a great place for those of you who, like me, are perpetually torn between looking up and looking down. Colorado’s spectacular geologic landscapes keep me occupied during the day, but at night a whole different world opens up overhead. Colorado is a great place to look at and photograph the night sky for several reasons:

  • It’s relatively dark. With the exception of the Front Range megalopolis (where I now live), there are few egregious sources of light pollution, especially when compared to just about every state east of here.
  • It has the highest average elevation of any state. This is important because looking through the Earth’s atmosphere at the stars is like looking through a glass of water at a friend sitting next to you. The higher you go, the thinner the atmosphere becomes, and the better and steadier your view of the night sky.
  • It has good weather. Clear skies can be found regularly throughout the year, unlike in the black hole of astronomy known as the Pacific Northwest.
  • It has lots of public land where you can theoretically spend all night outside taking photos without fear of getting shot.

I spent a good chunk of this past summer honing my astrophotography skills and if you’ve never tried your hand at it, I encourage you to give it a try. It has certainly made me a better all-around photographer. First and foremost, astrophotography is an exercise in patience, both at the camera itself and then in front of the computer afterwards, and patience is a valuable virtue in all aspects of photography. Ironically, as comfortable as I am outside under the stars, astrophotography actually pushes out of my comfort zone photographically. Apart from minor brightness or contrast adjustments and cropping, I tend to eschew significant post-processing of my photos. When photographing the night sky though, some quality alone time with Photoshop and Lightroom is pretty much a necessity in order to get something that looks good.

Milky Way stretching from horizon to horizon.

The summer Milky Way spans the sky from horizon to horizon as seen from near Delta, Colorado. The galactic center is located just above the southern horizon (right).

I’m not here to give you a step-by-step guide to night sky photography, that’s been done before (try here, here, or here), but simply to encourage you to try it. All you really need to get started is a DSLR, a tripod, some patience, and somewhere dark. Like ACTUALLY dark. Sadly, light pollution has gotten so bad that most people reading this will have never seen a truly pristine night sky. Driving to the suburbs does not qualify as “dark”. Here in the Denver/Boulder/Fort Collins light pollution-opolis, even after driving two hours up to 12,000 feet in Rocky Mountain National Park, you’ll still only see roughly HALF as many stars as can be seen with the naked eye from a truly dark location. To see if there are any pristine night skies near you, check out this nifty site, which is basically Google Maps with an overlay of light pollution severity. You’re looking for areas with the darkest black color and as you’ll see, they are becoming few and far between.

What’s great is how many different ways there are to incorporate the night sky into your photos. With wide-field astrophotography, the entire night sky is the star of the show (pun intended). Accomplished by using fast, wide-angle lenses combined with relatively short exposures (30 seconds or less, unless you have a motorized mount), this method can reveal spectacular detail in the night sky unseen by the human eye, such as the spectacular interstellar dust lanes in the Milky Way. If you pair the Milky Way with a terrestrial landscape illuminated by moonlight, the possibilities for composing spectacular nightscapes become nearly infinite.

Milky Way center close-up

Close-up of the center of the Milky Way Galaxy. Dark arms of starlight-obscuring dust, star clusters, and emission nebulae (pink) are visible in this 1-minute exposure.

Longer exposures (or lots of short ones “stacked” together) document the motion of the stars across the night sky. I have a soft spot for star trails because they are a beautiful reminder that the world we live in is in constant motion; the dramatic and graceful arcs traced out by the stars are due to OUR rotation, not the stars.  Star trails centered around the North Star (Polaris) can be especially striking since the north star is almost exactly above the rotational axis of the Earth, and thus moves very little throughout the night.

Star Trails over Escalante Canyon, Colorado

Star trails (centered on Polaris) over Escalante Canyon, Colorado

Probably the most challenging type of astrophotography, and really the only one that requires specialized (often expensive) equipment, is telescopic imaging. My experience in this category is limited, given the aforementioned factors (donations always happily accepted!), but I’ve tried it on a handful of occasions by using friend’s equipment or telescopes at observatories I have worked at. Telescopic astrophotography allows detailed images of galaxies, star clusters, and nebulae, many of which are not even visible to the naked eye. While good images can be obtained by fitting a DSLR to a telescope (below, center and right), the best images are obtained using stand-alone CCD cameras optimized for astrophotography (below, left).

Deep-sky images taken with telescope

A variety of galaxies and nebulae imaged via telescope. 

Some objects, like the Moon, are big and bright enough that a telescope is not needed to get decent images. I got this photo of last month’s total lunar eclipse with a standard 55-200mm zoom lens, and even had enough light gathering ability to capture the planet Uranus less than a degree away from the Moon!

Total lunar eclipse October 2014

Total lunar eclipse on October 8 2014, as seen from Fort Collins, CO

Beyond the technical challenge, what ultimately thrills me most about astrophotography is being able to capture photons that have been en route towards us across the vast universe for dozens, hundreds, or even millions of years. After that long of a journey, it feels like our duty to ensure that at least some of those photons have the honor of being recorded in some state of permanence. Give it a try and it won’t be long before you find yourself in the middle of nowhere waiting for your camera to finish a 1-hour exposure. A perfect change to sit back and ponder the vastness of the universe looming over your head.