Night sky photography

Photographing the night sky is quite a difficult task. From light pollution to the stars moving, there is a lot of variables outside of just the camera settings to take into consideration. Let me take you through how I do it! Scroll all the way down if you want to see the final image that I took.

The night sky over Valdemarsvik 2021-09-05 (cropped)

Chapter 1 – The Settings

When choosing settings for night sky photography the most important ones are focus, shutter speed and the ISO. Firstly we have to set the focus. Autofocusing on the stars won’t yield good result, instead we open the aperture as wide as we can, hopefully use a zoom function on our camera, and try to focus as good as we can on the start manually. Then we can stop down to a smaller aperture to our liking, like f2.0 or f2.8 for some extra sharpness.

Try closing down the aperture if you experience “cat eyes” in the stars.

Next we have to set the shutter speed. A too fast shutter speed wont let enough light in, and a too slow shutter speed will result in light streaks due to the stars moving (and yes you can clearly see the stars moving in just a couple of seconds). I think a shutter speed of 6 seconds is good, but you’ll have to try for yourself. A wider lens is more forgiving. There are special tripods that move the camera with the stars and enables you to take photos with minute long shutter speeds, but that is too advanced for us right now.

Next we have to set the ISO, here higher is often better, especially if you’re in a place with a lot of light pollution. A higher ISO will make the sensor capture more information in the sky, even though the ground may be blown out. To fix this we can take another image with a lower ISO to use for the ground in compositing.

Chapter 2 – Framing and location

Framing the image and choosing location might be the most important part of photographing the night sky. Without anything in the foreground of your image it might as well be an image with a bit too much noise in it. Look at these two images and tell me which one you like best.

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Image with a foreground

Make sure you have a steady tripod and firm ground underneath it. Set the camera self-timer on 2s, click the button and take 2 steps back. Even you moving can shake the camera if you’re not careful.

Finding a good location can be very difficult. Some are lucky and live far away from the city or have the possibility to find higher ground. Being in such a place is essential for taking good night sky photos. It just won’t be possible to see the stars and galaxies if there is a lot of light pollution in your area. Light pollution map has a great website where you can see just how much light pollution is in your area.

Light pollution maps can help you find great places for taking night photos.

Chapter 3 – The Advanced Stuff

When you have dialed in all the settings, found a good location, a sturdy tripod and are feeling comfortable we can move into some advanced stuff.

First we have image stacking. As I mentioned before, high ISO might be necessary to get a bright enough image, but will also result in a noisier image. To combat this we can do something called image stacking, taking several images and stacking them in Photoshop after the fact. Since sensor noise is random, taking two photos of the same thing (the same sky) will result in a different noise profile. Taking the median of these two images can then cancel out the noise in the image and keep only the stars.

– “But Fredrik,” you ask. “Won’t the stars move during the time between photos.”

Why yes, they will, and we will have to compensate for it by aligning the images in Photoshop as well. After we’ve aligned the images and stacked them with the median function, we might want to paste in the ground from the original image since it will have become blurry after aligning based on the stars.

If the Photoshop can’t manage to align the stars, try painting out the ground first.

And that’s it for now! I might update this post in the future with some more tips and tricks. Check out the resulting image below 😄

The night sky over Valdemarsvik 2021-09-05

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