Milky Way Photography: A Short Step By Step Tutorial
Updated 2020-12-08
This is a relatively simple astrophotography tutorial that will help you create stunning photographs of the Milky Way galaxy using your current photo equipment and image stacking.
Milky Way #1, Ontario, Canada, August 3, 2014
About the Milky Way
The beauty of the Milky Way's luminous river of stars stretches across the night sky, evoking awe and wonder like nothing else can. Here are some unimaginable Milky Way statistics.
The Milky Way is a spiral galaxy that spans 100,000 light-years in diameter.
It contains an estimated 100 to 400 billion stars (unfathomably huge range), each with its own solar system. There are at least 100 billion galaxies in the observable Universe.
Like everything in the universe, it’s moving. It takes 200-250 million years to complete one full rotation.
The Earth is located in the Orion spiral arm of the Milky Way. When we look up at the night sky, we're looking toward the galaxy's centre, where the concentration of stars is highest.
There are millions of black holes of various sizes throughout the Milky Way. At the centre lies a supermassive black hole called Sagittarius A, which has a mass of about 4 million times that of our Sun.
It's filled with numerous nebulae, which are regions of gas and dust where stars are born.
The Milky Way is estimated to be 13.6 billion years old, only 1.45% younger than the Universe.
Step 1: Equipment
For great Milky Way shots, you'll need a DSLR or mirrorless camera, a sturdy tripod, and a wide-angle lens with a low f-stop. A remote shutter release and headlamp are also useful.
For the above image, I used a Nikon D800 camera, Nikkor 14-24mm f/2.8 lens, Gitzo tripod with Ball Head, Adobe Lightroom and Photoshop. A faster lens is better as it lets in more light over the same exposure time. However, great images can still be made using "slower" kit lenses on entry-level or consumer DSLR and mirrorless cameras. The basic techniques should work with any camera that you can control the settings in Step 3.
Step 2: Location Scouting
Find a dark sky location away from city lights. Use apps like Light Pollution Map or Star Walk to find the best spots you can get to.
It's important to capture the images from a location with minimal light pollution, which is, sadly, increasingly hard to find. See this light pollution map. The quality of your results will be limited in urban areas.
The Bortal Scale was created to measures the darkness of the sky. See this informative post on the Bortal Scale and the impact of light pollution on astrophotography at NightSkyPix. My location for this image was a Bortal Class 4. For contrast, this image was taken in a Bortal Class 2.
Step 3: Camera Settings
Set the camera to "M" manual mode to specifically adjust aperture and exposure time.
Turn off normal noise reduction. The Photoshop image stacking process outlined in Step 6 will do a much better job.
Turn off long exposure noise reduction, or each capture will be twice as long while your camera creates a second, equally long "dark" exposure to subtract noise.
Turn off lens vignetting and distortion corrections as they can hurt stacking quality.
3200 ISO is a good compromise of exposure time versus digital noise on my D800. The higher the ISO, the more noise. Newer cameras may be able to use higher ISO values with less noise.
The "500 Rule" is often used to determine the number of seconds you can expose without seeing any star trailing as a result of the Earth's rotation on a full-frame camera. 500 divided by my focal length of 14mm = 35 seconds. However, because of my camera's high resolution, I found that even 20 seconds showed some star trailing, albeit what I consider to be acceptable. For my needs, a "300 Rule" is more applicable to the D800. Smaller sensor cameras will use an even smaller value to divide into. You'll have to do some experimenting. Note that an f/2.8 lens (faster) will gather the same amount of light in 20 seconds, and an f/4.0 lens (slower) will gather in 40 seconds. Each full f-stop decrease will halve the exposure time, and every full f-stop increase will double the time needed for the same exposure.
Set the white balance to 3600K, although it will be likely be modified during post-processing.
Images should be saved in RAW format for maximum post-processing control and the greatest dynamic range.
If your camera has an exposure delay mode, use it to prevent the vibration caused by mirror slap. This is not an issue with mirrorless cameras as there is no mirror.
Step 4: Use a Tripod
Use a solid tripod to make sure the camera doesn't move or vibrate in the wind. You may have to weigh your tripod down to make it more stable.
Step 5: Focusing on Infinity
Set your focus to infinity. Note that the infinity marks on most contemporary lenses are inaccurate, so I either use magnified live view to manually focus or autofocus on one of the brightest stars or planets. I turn off autofocus once the focus is locked and confirmed with a test shot, preventing the camera from hunting for focus in the dark sky.
Step 6: Image Stacking for Noise Reduction
I utilized image stacking to create this photograph. Many photos are combined to increase the signal-to-noise ratio of high ISO images resulting in a cleaner and more detailed photo. Another option for less noisy results would be to decrease the ISO, but that would increase the exposure time, resulting in star trails, which I didn't want. A third option would be to use a star tracking device like an iOptron Skyguider Pro that moves the camera in perfect sync with the Earth's rotation allowing for very long exposures at low ISO. Here is a great review of the pros and cons of the current portable star trackers, as of 2020, at AstroBackyard. Since I didn't have one, I opted for the stacking technique.
I used my camera’s built-in intervalometer to take a series of photos, one after another. If your camera doesn't include an intervalometer, you will need to get one. See more about intervalometers at NightSkyPix.
The images were imported into Lightroom for basic colour correction work and exported as 16-bit TIFF files. I then switched to Photoshop. Under Scripts in the File menu, I selected Load Files into Stack... and made sure that "Attempt to Automatically Align Source Images," necessary to counter the Earth's rotation over the course of the exposures, and "Create Smart Object after Loading Layers" were both checked. Once Photoshop was done processing, I went to Smart Objects in the Layers menu and changed the Stack Mode to Median, which is the magic of this stacking technique. The noise was greatly decreased while the details were increased.
Step 7: Post-Processing
Enhance your final image in Lightroom or Photoshop by adjusting contrast, highlights, colour, etc.
Quick Tips Summary:
Scout a dark location and plan ahead.
Use a wide-angle lens with the lowest f-stop possible.
Start with 20-second exposures at ISO 3200 and adjust.
Consider stacking images for improved clarity.
By following these steps, you’ll be able to capture stunning Milky Way photos and reveal the beauty of the night sky! Let me know if you have any questions in the comments below.
Explore the night sky through my astrophotography portfolio, showcasing the Milky Way and other celestial wonders.
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