1. Introduction
Amateur photographers can now photograph the drama of the night sky, thanks to digital cameras. Here are several ways to try astrophotography, from simple to more advanced:
- Create Milky Way and nightscape images with a tripod-mounted camera and wide angle lens.
- Put your camera on a motorized sky tracker for richer and more detailed images.
- Attach your camera to a small telescope or telephoto lens mounted on a more advanced tracker (“equatorial mount”) to photograph colorful nebula, distant galaxies, and more.
Night sky photography has special requirements beyond your typical daytime shooting. Some of the challenges to overcome:
- The sky slowly moves, causing star “trailing.”
- Noise is prevalent in long exposures of low-light subjects.
- Dark skies are becoming harder to find.
- Results straight from the camera often look terrible, and require some new processing skills to produce attractive images.
- You'll need to stay up late.
But you'll be rewarded for your efforts. Seeing the Milky Way stretch across a truly dark sky will take your breath away. You'll discover that your camera can see beautiful things in a dark sky that your eyes can't. And it may introduce you to the wonders of the Universe far beyond our tiny blue planet.
Milky Way and Ancient Bristlecone Pine
A 180° panorama of the Summer Milky Way. EOS 6D and 24mm f/1.4 lens. ISO 6400, 30 sec. White Mountains, CA (2018).
2. Milky Way Nightscapes
This is the easiest place to start, and the most familiar to anyone who has done landscape photography.
"Nightscapes” are simply night landscapes, and depend on including a dramatic landscape as your foreground against a night sky. And while the Milky Way is a popular subject, other parts of a star-filled sky can work just as well.
Milky Way and Lone Pine Peak
Panorama of 4 frames with a Rokinon 14mm f/2.8 lens, Canon EOS 6D from the Alabama Hills, Eastern Sierra Nevada. The landscape is illuminated by the glow of the Milky Way. Lone Pine, CA, 2017.
With your camera on a tripod, you will always get some amount star “trailing” as the sky moves: at 100% zoom, you’ll see the stars have left little lines instead of registering as points. This pretty much limits you to very wide angle lenses and exposures under a minute. If you zoom in closely, you’ll see a little trailing, but you’ll barely see it when you look at the full image.
The trick is to use as wide and as fast a lens as possible. The wider then lens, the smaller the trailing on the image. (My favorite lenses are in the 14-24 mm range.) And fast lenses let you use a much shorter exposure time. If an f/2.8 lens requires a 60 second exposure, then at f/1.4 you’ll only need 15 seconds—a huge advantage to reduce trailing.
Because you’re photographing a subject with very little light, you’ll need high ISO speeds, so a low-noise camera is an advantage. I typically use a Canon EOS 6D or 7D Mark II, which are quite low noise. And my ISO speed is never lower than 1,600—and sometimes as high as 12,800! And noise increases with exposure time as well as with ISO.
Star Trails around Polaris
You can take advantage of the moving sky to create star trails. Take a single long exposure, or combine many short exposures in Photoshop as I did here using 100 shots of 30 seconds each. The foreground is the remote Racetrack Playa in Death Valley, one of the darkest places I have ever been. Death Valley National Park, CA, 2015.
This is where your image processing skills come in. Most photographers never imagine that these cameras can perform well at such high ISO speeds. But modern noise-reduction software can do an amazing job and save the day (night). Now, if you pixel peep at 100%, it will look pretty bad. So don’t do that! If your overall image looks good, you’ve gotten a good shot (so don’t peek under the rug).
By the way, you won’t be able to autofocus on the stars, so you’ll want a camera with Live View, where you can zoom in on a star and focus manually. Focusing through the viewfinder at night is next to impossible with a wide angle lens.
Before you run out and buy a fast wide angle lens, be aware that some of the finest lenses are not good for stars! Stars a bright little points of light, and many lenses have aberrations that will stretch them into weird shapes (especially at the edges of the frame). Thankfully there are a lot of inexpensive lenses that happen to perform well in this arena. (And you don’t need autofocus or image stabilization.)
3. Sky Trackers
A simple motorized platform that moves at the same rate as the sky will virtually eliminate the star trails you got on your tripod. There are now a number of sky trackers on the market that will do the job and are simple to use. You’ll need to learn to align the rotation axis of the tracker with that of the Earth. In practice this means pointing it at Polaris, the North Star (in the northern hemisphere). But they come with simple “polar alignment scopes” that help accomplish that.
Then it’s a matter of attaching your camera and taking a long exposure (several minutes), or maybe a series of exposures that you can combine or “stack” in software, to reduce the noise and increase your all-important Signal to Noise Ratio (S/N or SNR). Stacking will make your subject stand out more clearly, show finer details, and reduce the apparent noise.
Several manufacturers offer sky trackers in various models. I currently use the Sky-Watcher Star Adventurer and Sky-Watcher Star Adventurer Mini that I put on a sturdy tripod.
Some things you can accomplish with a sky-tracker:
- Use longer exposures (several minutes), so having a fast f/1.4 lens and extreme ISO speed are not as important.
- Use longer focal lengths, perhaps up to 200-300 mm. You can frame some nice “deep space” vistas (such as the Andromeda Galaxy).
- Easily travel with it because of its light weight, by plane or even in a backpack. I took mine to South America to photograph the Milky Way in Chile. (The southern sky and Milky Way above the Southern Hemisphere is quite different from what we see in the north, and in many ways is more spectacular.)
- At long exposures, your camera will be able to pick up things in the sky you can’t otherwise see. (You'll want to learn more about the night sky, to know where to point your camera.)
- Stack images in software to dramatically increase your SNR.
The Southern Cross
The four main stars of the Southern Cross are sharp in this tracked image using a 135mm lens. The camera and lens were mounted on a Sky-Watcher Star Adventurer sky tracker, allowing me to take a series of fifteen 60 sec exposures that I later combined to reduce the noise. Several star clusters are visible, detail that wouldn't be sharp without a motorized tracker. Rio Hurtado, Chile, 2017.
Rho Ophiuchi Molecular Clouds
The colors seen here are invisible to the naked eye in this 135mm lens view. But in a series of 150 sec exposures their beauty is revealed, as bright blue and orange stars illuminate surrounding clouds of dust. Sky-Watcher Star Adventurer sky tracker. The dark streams are clouds of interstellar dust that obscure the Milky Way stars behind them. Rio Hurtado, Chile, 2017.
Coalsack in Southern Milky Way
This is a 2x2 mosaic of four frames shot with a 50mm f/1.4 lens on a Star Adventurer sky tracker. Each exposure was 30 seconds at ISO 3200 and stopped down to f/2.8 for increased sharpness. Seen here are the Coalsack dark nebula at left, the four stars of the Southern Cross, and the Eta Carina Nebula at right. Rio Hurtado, Chile, 2017.
For exposures longer than 30 seconds, you’ll need an intervalometer, which is basically a cable release with a programmable timer that can take one, or many, long exposures, with the correct connection for your camera. And you can use longer focal lengths (in the range of 200-300 mm) to zoom in on smaller targets.
These trackers can support a limited weight before they start to strain and trailing appears. If you long for greater magnification and longer focal lengths, you’ll need something bigger, which I cover in the next section.
4. Long Lenses and Equatorial Mounts
Now we’re getting into more serious astrophotography, but something still accessible to amateur photographers. And the number of things to photograph is almost limitless (although in practice this is bounded to a degree by the amount of money you’re willing to invest).
You’ll need a much beefier and more capable version of a star tracker, which in astronomy is known as a German Equatorial Mount (GEM), to follow the sky. But it will support the weight of a big telephoto lens or refractor telescope (which is basically a telephoto lens optimized for the stars).
As in bird photography with a big lens, the smallest vibration will be magnified and spoil your shot. For long focal lengths and high magnifications, an equatorial mount provides good performance, but weighs much more than a portable sky tracker.
A 500mm Lens on an Equatorial Mount
This heavy Canon EF 500mm f/4 lens requires a sturdy Equatorial Mount to track the sky. At bottom right is a movable 20 lb. weight to counterbalance the load. The mount is a Software Bisque Paramount MYT, an advanced computerized mount for astrophotography.
The Triangulum Galaxy
The spectacular spiral Triangulum Galaxy was imaged with a 500mm lens and EOS 6D camera on an Orion Atlas EQ-G equatorial mount, a sturdy and capable platform to accurately follow the stars. It required a total exposure of 1.8 hours from a dark desert sky, and careful processing in Adobe Photoshop and Lightroom. The light in this shot began its journey to my camera 3 million years ago ... a long time ago from a galaxy far far away. Panamint Valley, CA, 2014.
Equatorial mounts start at close to a thousand dollars, and you can easily move up into the thousands—or tens of thousands—of dollars. But the high-end mounts are meant for huge (and hugely expensive) telescopes, and as a beginner, you don’t want to go there. Excellent results are possible with mounts in the $800-$2,000 range, and such a mount could satisfy a lifetime of astrophotography. You can get impressive images with a large telephoto lens (e.g., 300/2.8 to 600/4). Or you can add a refractor telescope (essentially a telephoto lens, but designed for the stars) with an adapter for your camera.
Advantages of an equatorial mount:
- Holds much more weight and tracks the sky much more precisely.
- Many have “GoTo” capability—a computerized hand-controller with a database of tens of thousands of targets to view and photograph. You select one, press Go, and it quickly moves (“slews”) to your target and tracks it through the night.
- You can use a reasonably priced refractor telescope ($500-$2,500) with excellent results (it’s designed for one thing: sharp pictures of the night sky at infinity focus) and is usually much easier to focus than a lens. It is also easier to attach to an equatorial mount.
Some challenges:
- There is a learning curve to working with an equatorial mount to make it track well enough to give you round stars.
- You will want to learn about the thousands (billions and billions) of targets that are out there that you can see and photograph.
- You can learn more advanced processing techniques to make your images even better.
- There’s a temptation to get the biggest telescope you can possibly afford. Don’t! A big scope will magnify your view of distant galaxies, but it will also magnify every little defect and tracking error in your system, every vibration from every tractor trailer truck that passes on nearby highways, and every little breath of wind. Worse, it will have such a steep learning curve that after years, you may never get a satisfying image, you’ll hate this, and you’ll dump it all in the garage or basement to forever gather dust. Start small! Maybe all you’ll ever need is that sky tracker.
5. Final Considerations
The importance of processing
Images of the night sky straight from your camera often look very unappealing. They are often washed out and bland; the sky color can look unnatural; important details might not be apparent; and noise levels are high. The digital processing you perform after shooting is an important aspect of creating great results.
Although dedicated astro-imaging software exists (especially for specialized techniques like averaging or “stacking” several images into one), you can get excellent results with familiar processing tools. I use Adobe Lightroom and Photoshop the most, especially for the Milky Way and nightscapes.
Photographers are usually surprised to learn that the night sky is not really black, even in the very darkest locations. Light-pollution will add unnatural colors that you need to correct. But far from light pollution, there are other sources of color in the sky, such as airglow (emission from excited atoms and molecules high in the atmosphere).
As you learn the techniques needed for processing night images, you'll be able to turn your raw data into pleasing and natural images. Here is an example of an image before and after processing.
Before and After: Milky Way Panorama in Lightroom
Careful processing can transform your initial images into dramatic nightscapes. (The starting image was first merged into a mosaic in Lightroom.) White Mountains, CA, 2015.
Travel to darker skies
Nightscape photography will lure you to dark skies and scenic landscapes. Light pollution is a constant obstacle for night sky photographers. It’s sad to think of how many people live in such light-polluted skies that they barely or never see the Milky Way. (Helpful tip: The light of the moon will also interfere which your attempts to view and photograph the Milky Way; check your calendar for the dark of the New Moon.)
I’m lucky to now live in a small town in the Mojave Desert of California, not far from the vast expanse of Death Valley, and some of the darkest skies in the US. It is also a region of beautiful wide-open landscapes.
The next time you’re planning a photography trip, check a light pollution map and plan to head for dark skies. You won’t be disappointed.
The other hemisphere
When you travel south of the equator, you’ll find a night sky that is very different – and in many ways more spectacular—than the Northern Hemisphere sky.
The bright center of the Milky Way barely rises above the horizon in the northern hemisphere. But south of the equator you can find it overhead and more prominent. Two of the best globular clusters (balls of thousands or millions of stars bound close together by gravity) are easily visible to the naked eye in southern skies. And the Magellanic Clouds – two small satellite galaxies of our Milky Way – circle the South Celestial Pole and are easily visible.
The Magellanic Clouds
The Magellanic Clouds are easily visible to the naked eye in the Southern Hemisphere, rising and setting around the South Celestial Pole. Canon EOS 6D with Sigma 50mm f/1.4 lens
The Large Magellanic Cloud
A closer view of the Large Magellanic Cloud. Canon EOS 6D with Rokinon 135mm f/2 lens.
47 Tucanae Globular Cluster
47 Tuc is a cluster of over a million stars and one of the wonders of the Southern Hemisphere sky. Canon EOS 7D Mark II on tracked refractor telescope.
If the night sky captures your imagination, plan on traveling to dark sites in the Southern Hemisphere for more night sky wonders.
Conclusion
Amateur photographers now have to tools to image the night sky. From Milky Way landscape images to photos of distant galaxies, you can do it with a digital camera and careful processing.
Start with your camera with wide angle lens on a tripod. Move on to star trackers that follow the motion of the sky. Advance to equatorial mounts and small telescopes for even more detailed images.
I hope this has given you a flavor of what you can try. In future articles I’ll explore these techniques in more detail.