Background and Planning
Living in an urban area provides an obvious challenge for a night sky photographer. If I decide to walk outside my house after dark and look up into a clear night sky, all I’ll see is an orange glow and, if I’m lucky, a few of the brightest stars and planets. As a result, the first step of photographing the Milky Way for me is to find a location far away from the lights and glow of Boston.
In the Northern Hemisphere, the Milky Way is visible at some point during the night from February until October. After last year’s Milky Way season ended for me, I spent much of my winter scouring Google Earth and light pollution maps for possible locations to photograph the night sky in 2016 within a half day’s drive of Boston.
Recently, after the forecast for one of my planned locations turned cloudy at the last minute, I called a late-night audible and opted to drive two hours south to the ocean along Cape Cod instead of north into the woods of Maine. I try to follow a variety of different weather services to get a range of forecasts, but the ones I tend to find most useful for planning night sky photography are Weather Underground, due to their hourly cloud cover predictions, and Clear Dark Sky, which provides forecasts specific to astronomy. From checking the light pollution map, I knew that the beaches near Chatham, Massachusetts would be dark enough to see a good view of the Milky Way. And from checking apps such as PlanIt! for Photographers on my Android phone and Stellarium on my laptop, I knew when the Milky Way would rise (about 1:30 a.m.), in what direction (southeast), and that the moon would not interfere with the dark sky.
Not having an exact image in mind, I arrived on Cape Cod an hour before the Milky Way was set to rise, as I wanted to give myself enough time to wander around in the dark and find a few possible foregrounds I could include in my image. I try my best to visit my nightscape locations in daytime before I arrive in the dark, but there are times when both the weather and the distance of locations from where I live make this difficult to follow through on.
After spending a few minutes allowing my eyes adjust to the darkness and realizing that hide tide had swallowed up nearly the entire beach, I followed a sandy path along the beach’s sand dunes trying to find something that could provide interest to what otherwise seemed like a landscape of fine sand and dune grass waving in the wind—something that probably wouldn’t hold still for the long exposure the darkness would require. Once I noticed the core of the Milky Way beginning to rise over the southeastern horizon, I settled on a small bush poking out of the middle of the pathway I had been walking, deciding that it would serve as a focal point I could use to fill the foreground of my frame.
Given that the small bush I found was under a foot in diameter, I placed the front of my Tamron 15-30mm f/2.8 lens about 12 inches away from the plant, hoping that it would fill up much of the lower third of my image. I set my focal length to 20mm on my full frame Nikon D750, as it provided a nice balance between giving the plant some size in the frame, while still being wide enough to show the core of the Milky Way in all of its glory. Lastly, I made sure my camera was set to capture RAW files, as this would give me the flexibility I would need later on to get the most out of the image.
Whenever I take a night sky photo that will involve a blend of multiple exposures and the Milky Way is already where I want it to be, I always take any and all sky exposures first. Even if there are no clouds in the sky—which was the case with this image—I still focus on the sky first before moving on to other parts of the image. I’ve been burned before…
The shot above, named “Between the Dunes”, is ultimately the result of 9 individual exposures. After using Live View on my D750 to zoom in on a bright star and twisting the focus ring to make that star the smallest point of light I could, I took 4 sky exposures with an aperture of f/2.8, an ISO setting of 12,800, and a shutter speed of 13 seconds. While these settings caused some noise in the image due to the high ISO value, they allowed me to shorten my shutter speed. The goal of using this method for sky exposures is not only to make stars small points of light instead of small streaks (which could happen from using a longer shutter speed), but also to stack the exposures of the sky in Photoshop in order to increase the signal-to-noise ratio, thereby increasing detail in the Milky Way and reducing noise in the sky.
After taking my sky exposures, I switched my attention to capturing the entirety of the foreground and midground in sharp focus. To do this, I started by leaving my focus ring at infinity, lowering my ISO to 1600, stopping down my aperture to f/4, and increasing my shutter speed to 185 seconds. The reason for stopping down my aperture slightly was to slightly increase my depth of field, thereby reducing the number of images I would need to get the whole scene in focus. I reduced the ISO to 1600 in order to lessen noise in the foreground, and lengthened the shutter speed as a result of changing the other two settings, knowing that it would be needed to achieve a bright enough exposure. After each foreground exposure I captured, I pulled the focus in further and further until I had frames that showed every part of my foreground and midground sharply. Although this process is time-intensive, I’ve always liked taking long foreground exposures, if not just because it gives me time to take a step back and enjoy the night sky without having any other distractions.
After capturing a few more shots along the beach and retiring to my car for a much needed nap, I drove the two hours home to Boston to get a proper amount of sleep and begin processing my photos. Upon loading any RAW file into Lightroom, my first step is always to go into the Lens Corrections tab in the Develop Module and apply corrections for chromatic aberrations and the lens profile for the lens I used. I also scrolled down to the Camera Calibration tab and change the profile from “Adobe Standard” to “Camera Standard”, since I find that this typically provides better colors and contrast in the image right from the start.
After completing these tasks, I focused on getting the proper white balance in the photos by increasing the Vibrance and Saturation sliders to +100. By doing this, the colors on the photo became extremely exaggerated, which allowed me to better see the effects a small shift in the White Balance slider produced. I find I tend to keep the White Balance in my Milky Way shots somewhere between 3700 Kelvin and 4100 Kelvin, which avoids making the sky either too blue (which results from a lower White Balance temperature) or too orange (which results from a higher White Balance temperature). I this case, I found that 4000 Kelvin yielded a good balance between the Milky Way and the green and red airglow in the surrounding sky. I also added a slight magenta tint by pushing the Tint slider to +14. In my foreground exposures, I found that a White Balance of 4200 Kevlin and a Tint of +16 yielded the colors I was looking for.
Knowing that I was going to be bringing multiple exposures into Photoshop for stacking and blending, I minimized the other adjustments I performed in Lightroom for the time being. I adjusted the sky exposures by bringing down the Blacks slider to -20, increasing the Whites slider to +30, and increasing the Clarity slider to +30, all of which provided a bit of contrast to the Milky Way, which looked fairly flat and washed out in the initial RAW capture. In my foreground exposures, I increased my Exposure slider to +0.50, my Shadows slider to +70, my Whites slider to +38, my Clarity slider to +20, and decreased my Blacks slider to -30. After completing these initial adjustments in Lightroom, I selected all of my sky and foreground exposures and clicked Photo>Edit In>Open as Layers in Photoshop.
Once all of my sky exposures and foreground exposures were loaded into Photoshop as individual layers, I began the process of stacking them in order to produce the final image. The purpose of stacking the sky exposures was to increase the signal-to-noise ratio, which ultimately increases detail in the Milky Way and decreases the grainy noise that is the result of using a high ISO setting. The purpose of stacking the foreground exposures was to take the sharpest parts of each image and combine them to get crisp front-to-back focus. Given that the Earth rotated enough between each exposure for the positions of the stars to move from frame to frame, my first step was to align the sky exposures. I did this by painting a black layer mask over the foreground in each sky exposure to hide everything but the sky, selecting all of the sky exposures, clicking Edit>Auto Align Layers, and leaving the automatic settings selected. The result of this process was a perfectly aligned sky across each of my four sky exposures. It’s worth pointing out, however, that if I had any clouds in the sky exposures, the Auto Align Layers function would have trouble aligning them properly. Afterwards, in order to stack the sky exposures, I deleted each layer mask, selected all of the sky layers, and clicked Layer>Smart Objects>Convert to Smart Object. Once the layers were finished converting to a Smart Object (which is a fairly slow process on my laptop…), I selected the Smart Object and clicked Layer>Stack Mode>Median, which effectively selected the parts of the sky which appear in the same place in each image (the “signal”), and got rid of the noise that appeared randomly across each image. Although it’s a bit time consuming, I’ve found that this is the most effective way to reduce noise in an image.
Once my sky exposures were stacked, I switched my attention to my foreground exposures. Since the ground and camera stayed still between each exposure, there was no need to align the layers like I did with the sky exposures. Instead, I selected each foreground layer and clicked Edit>Auto-Blend Layers and selected “Stack Images”. This process allows Photoshop to automatically align any portions of the foreground exposures which may have shifted slightly as a result of changing the focus, as well as select the sharpest parts of each image. In this case, Photoshop did a great job stacking the exposures and created a blend that showed sharp focus from the dunes near the horizon all the way in to the grain of sand in front of the bush in the foreground. Since I was happy with the blend, I then flattened the foreground exposures and used a layer mask to blend the stacked sky layer with the blended foreground layer. Lastly, I flattened all of these layers to create a single image.
Given that the resulting image still looked a bit flat to my eyes, I added a Curves Adjustment Layer by clicking Layer>New Adjustment Layer>Curves. I used the Curves adjustment to add contrast to the image by dragging the left side of the curve down slightly, and dragging the right side of the curve up, which effectively darkened the shadows and increased the highlights. I then saved the file as a TIFF with the intention of bringing it back into Lightroom to add some finishing touches.
My final touch on “Between the Dunes” was to bring the resulting file back into Lightroom and add an adjustment brush to add a bit more detail and color to the Milky Way. I did this by going back into the Develop Module, clicking on the Adjustment Brush (the button farthest to the right below the histogram), and painting over the Milky Way and airglow in the image with a 50% density brush. I then adjusted the brush’s Contrast to +50, Highlights to +25, Clarity to +70, and Saturation to +30 to make the core of the Milky Way and airglow pop a bit more. The last step was to crop slightly to take a bit of dead space off of the bottom of the image.
The capture and processing associated with “Between the Dunes” was definitely a labor and time-intensive effort. With not much in the foreground to work with at my shooting location, I knew that using such a small bush to bring more interest to the image would require focus stacking, which meant taking five 3-minute exposures instead of just one. I also knew that I liked the composition enough that I would want to be able to print it cleanly later on, so I took special care to capture and process the photo in a way that would result in the best sharpness and least amount of noise. If I only had plans to share the photo online, between the low resolution and compression that the resulting image would be viewed at on Instagram or Facebook, it wouldn’t have been worth the time to stack sky exposures. In the end, however, that extra effort produced a good, clean image that I’ll be able to make large prints of, and hopefully sell in the future.
One thing to keep in mind is that post-processing is highly personal and subjective. The RAW files that went into making this photo could have been edited countless ways to produce very different final product. My goal in walking through the process step-by-step is meant not only to show how to make a image to look similar, but also for everyone to see where they may have chosen to do things differently. Overall, I hope knowing this process motivates you to get outside, try night sky photography for yourself, and make an image that is unique to your style.