Astrophotography 101

When it comes to taking photos of the night sky, we often find ourselves driving and hiking hours from any artificial light source, relying only on the stars and airglow in the atmosphere to light our entire frame. The conditions for astrophotography can prove to be very challenging to shoot in and push our gear to its limit. To come back with the best possible image, it’s important to head out with the right gear at the right time.

Over the last few years, with camera sensors continuing to improve in extreme low-light situations, the technical challenges of astrophotography have eased. Astrophotography today is more accessible than ever before. These tips will help you head out under the night sky to capture beautiful photos of the stars.

Gear For Astrophotography

While there are “ideal” selections in each of the following gear categories, there are also ways of adjusting your shooting technique to compensate for equipment shortcomings. I’ll note these as we go.

Camera Body

While certain cameras will produce cleaner results at higher ISOs than others, most DSLRs and mirrorless cameras released in the last five years or so can achieve quality results. Features that assist with long exposures and remote control options via smartphone apps are great to have.

Lens Choice

The right lens will make a world of difference at night. Ideally, your lens will have a fast maximum aperture of at least ƒ/2.8. Prime lenses sometimes offer even faster apertures, which can be a huge advantage for picking up extra detail in both the sky and foreground. Selecting a lens that is sharp from edge to edge is also especially important. Since the edges of our frame at night will be filled with pinpoint stars, any flaws of a lens will be much more apparent.

When it comes to picking a focal length, don’t limit yourself to the traditional wide- or ultra-wide-angle lenses used for astrophotography. These are generally great choices, but select your focal length to best suit the composition you have in mind.

McWay Falls, Big Sur. The iconic Big Sur coastline provides surprisingly dark skies with incredible views of the Milky Way.

Tripod

Typical exposure times at night can range from five to 30 seconds—or much longer if you want to capture star trails. Ensuring that your camera stays steady during these exposures will be critical in achieving a sharp image. A sturdy tripod is key.

Shutter Release

If your camera doesn’t have a companion smartphone app that allows remote control, an optional hardware remote or mechanical shutter release cable will help avoid any shake from manually pressing the shutter. If you don’t have any of these, setting your camera’s shutter delay timer to about five seconds should eliminate camera shake caused by activating the shutter, but when taking multiple exposures for star trail composites or meteor showers—or whenever you’re shooting on Bulb exposure mode—a remote of some kind is essential gear.

Headlamp

Trail illumination is safety equipment at night, especially in wilderness areas where you’ll find the best conditions for astrophotography. A red light in your headlamp will help keep your night vision intact while providing enough visibility to navigate safely.

ASTROPHOTOGRAPHY TIMELAPSE

How To Plan Night Sky Photos

The most important element to capturing a successful photo of the stars begins with the location. A great view of the stars requires as little light pollution as possible and being there during the right moon phase.

Escaping Light Pollution

An easy way to ensure you’ll have an amazing view of the stars is by visiting a Dark Sky Park (darksky.org). The International Dark-Sky Association designates areas committed to protecting the view of the stars. Alternatively, you can search for light pollution maps of the area you hope to shoot. You can use sites like ClearOutside.com for detailed light pollution information for non-dark sky park locations.

Foreground Elements

Once you have a location as far from light pollution as possible, it’s important to make sure you’ll have an interesting foreground to elevate your image. A photo that captures mostly stars can be exciting but will often be less memorable than one with a strong foreground. If an element makes for a great photo during the day, there’s a good chance it might work at night as well.

Placing the Sky

Once your foreground is selected, the amount of sky you include in your image will have a strong impact on how it’s presented. For example, using just the top third of your image for the sky will force more attention on the foreground scene. Think of this as a “landscape at night” approach.

Framing an interesting foreground below two-thirds of night sky in a composition, the stars will be front and center. This might be your approach if you’ve found a great dark sky location and are framing the Milky Way across the sky.

There are no rules here; just be mindful that the balance of sky and foreground directs your viewer’s attention.

Effect Of Lens Focal Length

Choosing the right focal length for your location—or the right location for the lens you have available—is an important decision. The traditional choice for astrophotography is to use wide-angle focal lengths to capture as much of the scene as possible, but as mentioned above, longer, less commonly used focal lengths can also make successful images and might be the better choice depending on the scene.

Your focal length choice will have a big impact on the emphasis of your compositions. Ultra-wide angle lenses (14mm, left) are the most popular option because they capture such an expansive perspective, but longer focal lengths (24mm, right) can create more intimate viewpoints.

If you’re planning on framing up a towering mountain range, you may want to consider a slightly longer focal length than ultra-wide. Situations where you might be trying to capture a vast desert scene or plan on having a subject closer to the front of your composition might be better suited for a wide angle. My two photographs of Mt. Rainier, one taken with a 14mm lens and the other with a 24mm, illustrate the impact that a change of focal length can have on a photograph’s emphasis.

Moon Phase

For the most amount of detail in the stars, plan to be out during or near a new moon. In an area free of light pollution, this is when the stars will appear brightest, but keep in mind that it will also likely result in a very dark or silhouetted foreground. If foreground details are important to your previsualized image, shooting near a quarter moon will help add extra light to the landscape while still allowing you to capture the Milky Way.

Basic Camera Settings For Astrophotography

When shooting at night, the goal is to capture the most amount of detail while producing the cleanest (low noise) image possible. There are some general settings to know, understanding that they will vary depending on several factors, including camera, lens, location, moon phase and more. Use the basic settings to get started and experiment to adjust them for your scenario.

Camera Mode

I recommend using your camera’s Manual exposure setting.

Shutter Speed

A typical astrophotography shutter speed is 5 to 30 seconds. When selecting a shutter speed, you’re usually aiming for the maximum length of time you can expose while keeping the stars sharp. The exact time you can expose for is generally based off the size of the sensor in your camera and the focal length you’re using. Here are a few different methods to calculate your exposure time:

500 Rule

This method is slightly outdated with the introduction of better camera sensors but can still be used as a general guide to get started. To use this, divide 500 by your full-frame-equivalent focal length. For example, 500 divided by 20mm would give you an estimated 25 seconds. With some higher-resolution cameras, this may still result in very short trailing in your stars. If using this method, take a few exposures adjusting your exposure time shorter and longer to compare.

NPF Rule (Aperture, Photosite, Focal Length)

This method will calculate a very precise exposure time but is slightly impractical. The actual equation (35 x aperture + 30 x pixel pitch) / focal length will result in perfectly pinpoint stars. Thankfully, this function is available in smartphone apps like PhotoPills and Shutter Speed Calculator.

ISO

A suggested range for ISO is 1600 to 6400. The “right” ISO will change not only by situation but will vary greatly by camera. Although newer cameras are performing better and better at higher ISOs, the amount of noise at higher ISOs can differ dramatically. How much noise is visible at each different setting can be difficult to determine while reviewing your image in the field, so it’s best to take a series of images while increasing the ISO each time and review these to determine what looks best accurately. Experiment, and you’ll find the sweet spot for your camera.

Aperture

Aperture Effect. Your selected aperture can make a huge difference in the amount of light in your photographs. This split image shows the effects of two exposures taken within a few moments of each other, the only difference being the change in aperture from ƒ/2.8 (left) to ƒ/1.8 (right). Notice there is much brighter illumination in the ƒ/1.8 exposure. Though the stars and their reflections are less apparent in the brighter exposure, you can compensate for this by adjusting the areas separately in post-processing or by combining multiple exposures.

An aperture of ƒ/2.8 or larger (“faster”) will maximize the amount of light entering your lens. A faster aperture will make a world of difference when it comes to how much detail you’re able to capture in both your foreground and sky. The split image shown here of a starry sky reflected in a foreground lake was taken a few minutes apart with only the aperture changing from ƒ/2.8 to ƒ/1.8, illustrating the advantage of a larger aperture for light gathering.

Color Balance

Your color balance will be one of the biggest personal choices when it comes to capturing and processing your image. Daylight or 4,000-5,000 Kelvin will produce a warmer, more natural palette, while settings in the 3,000-4,000 K range result in cooler hues. The 4,000-5,000 K range will produce a more scientifically accurate image, but you might find the blue or cooler temperature for the image to be more atheistically pleasing.

In-Camera Noise Reduction

It’s important to turn off the long exposure noise reduction in your camera. If it’s on, the camera will take an additional exposure of the same length with the shutter closed to reduce noise in the final taken, which can mean waiting much longer between shots. Applying noise reduction in post-processing will allow for more precise control and save time in the field.

File Format

Use RAW. Having as much data available as possible will help you pull the maximum detail from the night sky and your foreground.

Jasper Meteors. This once-in-a-lifetime shot in Jasper National Park, Canada, captured four meteors in a single 10-second exposure. This frame came from the middle of a sequence of over 240 individual images taken during a very active Geminids shower in 2016.

Focusing The Stars

As a default, use manual focus set to infinity. Focusing to infinity will allow for most of your foreground all the way to the stars to be in focus. It’s important to closely review both the stars and foreground in your images as it is very easy to miss a slightly out-of-focus image when reviewing on your camera. The use of much higher ISO settings at night will also make determining focus slightly more difficult.

There are some additional methods for focusing you can try. If you’re setting up for a night shot during daylight, you can use autofocus to focus on the horizon. After your lens has focused, carefully switch back to manual focus to use that setting as a starting point at night.

You can also use your camera’s live view to focus. Start by placing a bright star or planet near the center of your frame. With live view on, magnify all the way in and very slowly adjust your focus. When out of focus, stars will have a bokeh-like appearance. As you adjust the focus ring, the star will become smaller and smaller and at the right spot will look like a tiny dot. If you adjust too far, it will begin to look like bokeh again.

Take a test image and review. If you’re having trouble with focusing, you can increase your ISO and decrease your exposure to save time between takes. Review each image and make small adjustments until your focus looks sharp, then reset your exposure to your preferred settings.

Having to determine the right settings for each image may seem tedious, but after a few outings, they will become second nature.

Advanced Techniques For Astrophotography

Depending on the time of day, moon phase, celestial events and your intended results, the approach that achieves the best photographs will vary. Here are some common conditions and how to adjust for them.

Twilight or “Blue Hour”

Shortly after sunset and before sunrise, there’s a transitional period referred to as blue hour. During this time, the sky isn’t completely light or dark, but there is a short window where stars will be visible. Capturing the stars as they appear with the last bit of fading color from sunset can result in a stunning image. This is also a great time to shoot with cameras that don’t perform particularly well at very high ISOs. With more available light, your shutter speed and ISO will be much lower than later in the night. Start with these settings for twilight: 5-10 sec., ƒ/2.8 or ƒ/4, ISO 1600.

Malibu Sea Cave. Twilight, or “blue hour,” can be an excellent time for astrophotography, blending sunset or sunrise hues with the stars.

I planned to capture my image of a sea cave in Malibu just as the moon would begin to disappear behind the rocks in the distance. The last bit of color from a beautiful sunset lingered just long enough to capture the stars as they slowly appeared in the sky.

Moonlight

Shooting while the moon is between half to full is similar to shooting at twilight. Your image will have less visible stars than shooting near a new moon but will have much more available light to pull detail from the foreground. Longer exposures under moonlight can even start to look like daytime images with stars in the sky, as you can see in my photograph taken at Zabriskie Point in Death Valley National Park. Full and half-moon phases can be a great time to head out if you have a lens with a slower aperture or a camera that struggles with noise. Start with exposure settings of ƒ/2.8 or ƒ/4 at ISO 800 to 1600, with a shutter speed of 5-10 sec.

Moonlit Scene at Zabriskie Point. A bright moon placed just out of frame lit up this famous vista in Death Valley. The amount of detail and color captured with the help of the moonlight make this a recent favorite image.

Milky Way

Quite often, the goal for anyone attempting to capture the night sky is an incredible photo of the Milky Way. For this to happen, you’ll need to be in an area free of light pollution while having your gear and settings all dialed and ready to go. Combing all of these will result in the most detail from the Milky Way possible. Figure out the longest exposure for your setup, how far you can push your ISO, and the darkest skies you can find with an interesting foreground, and you’re sure to have an image for your portfolio, like my photograph of McWay Falls under the Milky Way in Big Sur, California. Start with these settings: 10-25 sec., ƒ/1.4 to ƒ/2.8, ISO 3200.  

Star Trails

Star trails are typically shot in one very long exposure or by taking many consecutive long exposures. Taking multiple exposures will generally be a bit safer and an easier path to better results. When shooting multiple exposures, make sure your camera is set to a continuous shooting mode, and that you have an external remote. You have a bit more flexibility when it comes to your exposure time and can either select the maximum time for sharp stars or the longest available in-camera exposure time of 30 seconds.

Star Trails, Anza-Borrego Desert State Park, California. Without any large foreground objects, I chose an ultra-wide focal length and placed my camera low to the cracks in the dry lakebed. These star trails are the result of shooting for over three hours while placing Polaris in the upper right section of the sky.

To achieve the often-desired spiral or circle pattern, make sure to place the North Star, Polaris, in your composition, as the stars revolve around it. After you have your composition set, simply lock the shutter release on your remote and aim to shoot for 45 minutes or more, either with a single exposure or with multiple exposures that you combine later using star stacking software. Start with settings of ƒ/2.8 or ƒ4 and ISO 1600. If you’re shooting multiple frames to combine later, each should be about 10 to 30 seconds.

Meteor Showers

Shooting a meteor shower combines tips from multiple astrophotography scenarios. You’ll want to use settings like those for Milky Way images but a technique similar to shooting star trails. Shooting consecutive exposures with settings for sharp stars will give the best chance at capturing a meteor in your image. Meteors travel at incredibly fast speeds and can be difficult to capture. Just like when shooting star trails, the longer you shoot for, the better your chances of a great image. Start with settings of 10-25 sec., ƒ/1.4 to ƒ/2.8, ISO 3200.

Be Creative With Foregrounds

Most often, astrophotography compositions will be similar to that of landscape photography. With the ability of capturing more light through faster apertures and using an ISO much higher than previously possible, the door is open to a world of new possibilities. This might lead to more portrait-style images taken at night or even a blend of surf and astrophotography. One of my favorite images shown here was the result of a lot of experimentation and location scouting. A fisheye lens in an underwater housing was used to capture the moon setting next to the Milky Way, while a small waterproof light lit up the underwater portion of the scene.

Be creative with foregrounds. Employ a friend to add a human element to your scene or try something totally different like this image made with a camera in an underwater housing partially submerged.

Being out under a truly dark sky is an incredible experience, and being able to capture a small part of that can be just as exciting. With most of the world’s population unable to see the Milky Way, sharing your experience can be hugely inspirational to people who didn’t know this view of our night sky was even possible. Be ready to lose a lot of sleep, drink a lot of coffee and hopefully capture photos you’ll never forget. See you under the stars. 

See more Jack Fusco’s work at jackfusco.com.

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