As Numerous As The Stars

As numerous as the stars
With today’s cameras and lenses, it has never been easier to capture the stars and the Milky Way and get sharp, clean results. All it takes is some technical knowledge, patience and a good amount of practice. Before we start, I think it’s important to note that most of these images are the result of blending multiple exposures together in Photoshop. The technical details needed to get a low-noise and in-focus wide-angle image at night usually require multiple exposures, something we’ll go over in a bit more detail later in this article, but the basics apply to taking single images as well.

Finding The Milky Way

Before you can go shoot the Milky Way, you need to find out when and where you can see it. The Galactic Center of the As numerous as the starsMilky Way (the center of our home galaxy) is the biggest and brightest part that’s most often photographed. In the Northern Hemisphere, the Galactic Center is visible at night from roughly February through October. Early in the year, the Galactic Center is visible low on the horizon in the southeast, and throughout the year the Milky Way will rise more \vertically and move southwest through the sky. Things are different in the Southern Hemisphere, with the Galactic Center starting in the southwest and moving northeast and further through the year, and the Galactic Center is often much higher in the sky.

There are a number of handy iOS and Android apps available that display the location of the Galactic Center of the Milky Way. One of the best apps is PhotoPills, available for both iOS and Android, which shows the location of the Milky Way relative to any point on a 2D map, the perfect planning tool for landscape astrophotography. You can also check out The Photographer’s Ephemeris and PlanIt! For Photographers, which are similar to PhotoPills. The Photographer’s Ephemeris has an augmented reality mode, allowing you to point your phone at the sky and see the position of celestial objects at any date, time and location of your choosing. There are also lots of night sky guide apps available that will let you find the direction of the Milky Way, such as SkySafari, Star Walk, Planets, Star Chart and many more. There’s also Stellarium, a free desktop application.

Finding A Dark Sky

If you haven’t ever really noticed light pollution before, you’ll be amazed at just how far away from a city you have to get in order to be under a very dark sky. When planning your shots, make sure to note the location of cities near your desired shooting spot and where the Milky Way will be visible in relation to them. For example, if the Milky Way will be in the south part of the sky, don’t go north of a big city unless you go way, way far north. You can use a website like Dark Site Finder, http://darksitefinder.com/maps/world.html, to view a light pollution map and plan your shooting locations in as dark an area as you can.

Gear

Over the past few years, cameras have evolved tremendously when it comes to resolution, and you can get good results with a crop (APS-C, Micro Four Thirds, etc.) camera and a fast wide-angle lens, but you’ll still have the best results with a full frame camera. Modern full frame cameras such as the Nikon D850 have much better high-ISO-noise performance than cameras from just a few years ago. But I’ve also seen amazing results from the newer entry-level crop and mirrorless cameras from all brands.

Arguably more important than the camera is the lens, because the camera is only as sharp as the lens. For sky-filling images of the Milky Way, you want a large-aperture wide-angle lens that’s sharp with minimal coma distortion even at its largest aperture, or at least at ƒ/2.8. Coma distortion is a typical warping of an image found mostly on lower-end lenses. You want to capture as much light as possible in the sky over a 30-second or less exposure, so your lens needs to be pretty sharp even at its largest aperture or else you’ll get soft stars.

Some lens examples for full frame cameras include the NIKKOR 14-24mm F2.8, Canon EF 16-35mm f/2.8, Tamron SP 15-30mm F/2.8, and the Rokinon 14mm f/2.8. For crop cameras, some examples include the Tokina 11-20mm F2.8 and the Rokinon 12mm f/2.8 lens. Sony shooters will find great results with the FE 16-35mm G Master lens, and Sigma’s wide-angle ART lenses work great on Nikon, Canon or Sony.

Fujifilm shooters can try the XF16mmf/1.4 R WR, and Olympus and Panasonic photographers can use the M.Zuiko Digital ED 17mm f1.2 PRO, although the lens has an equivalent 35mm focal length, so isn’t as wide as some of the full frame choices.

You’ll also need a solid tripod to keep your camera motionless during long exposures, and an intervalometer or remote release so that you can take foreground exposures longer than 30 seconds. Some cameras have a built-in intervalometer, but most do not, so a programmable intervalometer like the Promote or Vello ShutterBoss will make life a lot easier vs. using a simple one-button remote release and a stopwatch.

As numerous as the stars

Capturing The Stars

To capture pinpoint stars, as opposed to long star trails, you need to use shutter speeds that are generally 30 seconds or less with super-wide angle lenses. The actual shutter speeds will depend on your focal length. A general rule of thumb is the “500 Rule,” which states that your focal length (35mm equivalent if using a crop camera) divided into 500 gives you a shutter speed that would have small amounts of star trails. However, I personally find this rule often results in star trails that are too long, so I usually go even shorter with the shutter speed. The best thing is to take test shots and see what works for you.

You also need to use a high ISO in order to capture enough light from the dark sky. Generally, ISO 3200 or higher is a good start. Too low, and you won’t get enough detail in the sky; too high, and you might get too much amplification noise in your shot, which often shows up as a magenta “glow” along the edges of the frame. Experiment to find the best result for your camera.

When shooting single exposures for the sky, I’m frequently at 14mm, f/2.8, 20 seconds, and between ISO 3200 and 12800, depending on the ambient light in the sky.

Star Stacking

You can create an image that has pinpoint stars with exceptionally low noise by using a technique known as “star stacking.” Using this technique, you take multiple, very short and very high ISO exposures of the stars, and then align and average those exposures together in software. The result has pinpoint stars due to the short exposure time and is very low noise due to the averaging of the noisy images. You can do the alignment and averaging in Photoshop by masking out the foreground in each image before doing the alignment, then putting the aligned layers into a single Smart Object and choosing the Median blend mode for the Smart Object. If you’re on a Mac, you can use the program Starry Landscape Stacker (available in the Mac App Store) to automate much of the star stacking process for you. You can then take the resulting star-stacked image and blend it with your foreground exposures just as you would with a single exposure for the sky.

For star stacking at 14mm and f/2.8 with my D850, I normally use ISO 12800 for 10 seconds and take 10 exposures. You should experiment to find what works with your setup. Some cameras will have a lot of magenta sensor noise on the edge of the frame when shooting a really high ISO for a short time, so keep this in mind and see how your camera performs. You may need to bring the ISO down to get rid of the magenta noise with these short, 10-second exposures.

As numerous as the stars

Focus For The Stars

Getting critical star focus at night can be a bit tricky, but if you aim the center of your lens at a very bright star and use live view, you might be able to see the star and rotate your focus ring manually until the star is as round and sharp as possible. Make sure to start with the focus ring near infinity because if you’re too far out of focus, the stars will be blurred so much that you won’t be able to see them at all. If you can’t use this live view method, then in daylight find the true infinity focus point on your lens by focusing on something far away on the horizon. You can then mark the spot on your focus ring or tape it down. Don’t rely on the infinity mark on your focus ring; infinity focus changes as the lens ages and with heat and humidity, and, on cheaper lenses, the infinity mark is often so far out of calibration that it’s meaningless.

Foreground Exposures

Since you need to capture the stars at a very wide aperture, focused for the stars and a very high ISO, this will often result in the foreground being out of focus, dark and noisy. By taking additional exposures for the foreground at different focus distances, much longer shutter speeds, and lower ISOs, you’ll have a cleaner and in-focus foreground that you can blend with your sky exposure in Photoshop to create a single photo that has pinpoint stars, low noise and the entire scene in focus.

When possible, I like to shoot my foreground exposures at ISO 1600 or lower, and the shutter speed can vary anywhere from 1 minute to 30 minutes, depending on the ambient light. You could use light painting to brighten the foreground so that you can use a shorter shutter speed, but this can lead to harsh shadows and blown-out highlights. I usually prefer to capture the scene using ambient light.

I often shoot my foregrounds at ƒ/2.8 and take multiple shots at different focus distances and then blend them for depth of field (focus stacking). I could take fewer shots at a higher f-stop for greater depth of field per shot, but using a higher f-stop means needing to keep the shutter open even longer to capture enough light, and in some very dark areas that might mean an exposure that’s multiple hours long. If something goes wrong in that exposure, you have to do it all over again.

You can judge your needed foreground shutter speed by doing some test shots and a little exposure math. Let’s say you take a shot at ISO 12,800 for 30 seconds just to check what you get for your histogram and detail in the foreground. If the scene is still really dark, try 60 seconds. This is just a test shot, and it will be very noisy, but we’re just looking to get an idea of how much detail will be visible in the foreground once we go down to a lower ISO and longer shutter speed. So if 60 seconds looks good, it’s then just a matter of some multiplication to get your shutter speed for a lower ISO. If you want to shoot your foreground at ISO 1600, then count the stops from ISO 12800 to 1600-12800, 6400, 3200, 1600—that means that ISO 1600 is three stops down from ISO 12,800. Multiply your initial test shutter speed by 2 for each stop down, and you get 1 minute * 2 * 2 * 2 = 8 minutes. Now you can shoot at ISO 1600 for 8 minutes, and your level of foreground brightness will be similar to or hopefully better than what you saw with ISO 12,800 for 1 minute, but the image will have much less noise. Note that this math assumes you didn’t change the f-stop, but if you need to change the f-stop in addition to the ISO, just do the same math for the number of stops you went up from the f-stop used with the test shot.

As numerous as the stars

Other Camera Settings

As always, you should be shooting in RAW mode to get the most out of your camera and editing ability. White balance isn’t important to a RAW file, but it’s important for the JPEG preview that you see on your camera’s LCD. Most cameras calculate the histogram they display based on the JPEG preview, so dialing in a white balance that comes close to what you might want your scene to look like will create a more useful histogram. I’ll often use a manual white balance of somewhere around 3800K-4000K in camera and then adjust the white balance in Lightroom.

I suggest using Long Exposure Noise Reduction for single sky shots or for long exposure foreground shots. This will reduce (hopefully eliminate) the hot pixels in an exposure, but in order to do so the camera has to take a “dark frame,” which is an exposure with the same settings but the shutter closed. The camera then uses the dark frame to find and remove hot pixels from the original exposure before writing out the final raw file to your memory card. This works great, but it doubles your exposure time. It’s not necessary if you’re doing star stacking, since the aligning and averaging will wipe out hot pixels.

Go Out And Shoot!

Now that you have the basics down, go out and shoot! Check your app for the Milky Way angle at a dark sky location and have fun!

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