Thanks for taking the time to check out this tutorial. I'm naming this article "How to Photograph Star Trails", but more accurately it should be called "How I Photograph Star Trails.” I’m sure there are plenty of people who do things differently than me. If you have any feedback/suggestions/questions/comments about anything on this page, please feel free to contact me, or leave a comment at the bottom of the page. I encourage discussion of the topic. This will be a live working document and I'll update it as I continue to learn new and/or better ways to perfect my system. Please feel free to share and/or link to this document if you'd like.
Things you might need:
1. Check the weather to be sure you are going to have a dry and clear evening. Here in Florida those nights don't come very often in the spring and summer, but all the time in the late fall and winter. I'm sure out west they happen all the time.
Composing the Image:
Focus: The first thing to do is establish focus. Basically, point the camera at a bright star or anything that is far away but bright, and half-press the shutter until it locks focus. Once you are satisfied with the focus, carefully turn off the auto-focus feature (you will usually find this on the lens). Then you won't have to worry about focus anymore. Just be careful not to change the focus by accidentally moving the focus ring or zoom ring on your lens. Also, when you are finished shooting your star trails, don’t forget to switch the lens back to auto-focus.
Compose: Once you have set up your tripod and established your focus point, you will need to compose your image. You will most likely want to use the widest focal length available to you, or something close to that. Obviously, the stars are the main ingredient for this project, but I've found that it's always desirable to have something from Earth in the foreground of the photo to give perspective to the star trails. I've done this mostly in my backyard, so the pine trees behind our yard have been my foreground for the most part. If you are interested in capturing the "circle" around the North Star, then you will need to know how to find it. This site has a good explanation on how to find the North Star. As you can see from my photos, our backyard faces the north. I've always loved the swirl effect that results from having the north star in the frame, but, to my surprise, my most popular star trails photo has been the one facing east, with my house as the foreground. The only explanation I can think of for this is not only does it add perspective, but it also adds "life" to the photo. That may be something worth considering when composing your photograph as well.
The Moon: If the moon is in the sky, make sure it is A) not in the frame, and B) not going to move into the frame during the course of the shot! Obviously the moon adds light pollution to the sky, but as long as it's out of the frame (preferably as far from the frame as possible) you can still record the star trails successfully. Just remember that any light that is in the area (the moon, streetlights, city lights) will decrease the amount of stars that you will see in your photo, so you will want to try your best to keep it to a minimum. You can see this by comparing my backyard shots to any that I've done elsewhere, where there is more light.
Determining your Exposure value:
Before I explain how to determine your exposure, I want to explain the basic premise of how I shoot all these images. In the "things you need" section, I wrote that you need a Wired Shutter Release with a mechanism to lock the shutter button down. Have you ever used the Sports setting on your DSLR? Or put the camera in burst mode? You hold the shutter button down and the camera just fires off photo after photo, without ever releasing the shutter button. This is precisely what you will be doing here, except on a longer, larger scale. Each shot will be a 30-second exposure.
Test Photos: It’s a good idea to take a few test shots and tweak the settings until the image you see on the LCD (the foreground as well as the stars) is exposed the way you are looking for. The first thing you will need to do is put your camera into "Manual" mode. This is normally the "M" on the dial at the top of your camera. The three settings that you will be concerned with when determining your exposure will be ISO, Shutter speed, and Aperture. As I said above, these all relate to each other. When one of these is adjusted, another one might need to be adjusted to compensate. Here is basically what you will be trying to achieve for each of these settings:
Aperture: Quick story: The first time I tried shooting star trails with my DSLR, I figured I could do it with one super long exposure. So I set up the camera and tripod in the backyard, fired off a few test shots, and found a composition where a good exposure would be 1 minute at f4 and ISO 200. Using the knowledge that I gained from the Understanding Exposure book, I calculated that I could get the same exposure by increasing it to 64 minutes, but changing to f/22 and ISO 100. I changed the settings, started the exposure with my wired shutter release, and went inside to watch TV. 64 minutes later I came back outside and stopped the exposure. When I viewed the photo on the computer, I learned two very important things:
1. The photo was very noisy and there were TONS of random colored dots all over the photo (I later learned these were called hot pixels). If you leave the shutter open too long on a digital camera, you will get more noise and hot pixels, which result from the digital sensor working overtime collecting all of the information in your photo. Remember that, unlike a film camera, your sensor is a piece of electronics that can (and will) heat up if you leave it running too long. This is why for me the best way to photograph star trails with a digital camera is to shoot multiple exposures, and combine them later on the computer. I have yet to determine what the longest acceptable exposure is, but if I ever experiment with that, I will definitely let you know. Most likely, each camera will have a different threshold, and each person will have a different opinion on what is acceptable.
2. The second issue that I noticed was that the star trails were VERY faint, almost to the point that you could not even see them. The lesson I learned here is that your aperture (aka f-stop) needs to be as close to "wide open" as possible. Which means you want your f/stop to be the lowest number possible. (f/2.8, f/4, f/5.6...). I do not recommend going any smaller than f/5.6. I'm sure the photo will be fine, but for each stop down of aperture, the less amount of stars and light intensity you are going to capture. Think of it this way: at the beginning of a 30 second exposure, a star will have an entirely different footprint in your frame than at the end of the exposure. Since it is moving so quickly, you want to be able to capture as much light as possible at each position that it is in (wider aperture = more light into the sensor at any given moment).
If you find that an aperture of f/5.6 is still causing your foreground to be overexposed, then I would suggest finding a different place to shoot from. Conversely, if your aperture is as wide open as possible, and your foreground is still underexposed, I recommend bumping up your ISO, but not too high (see "ISO" below for more details).
Shutter speed: For this method, the shutter speed needs to be exactly 30 seconds. The only reason for this is because 30 seconds is the longest shutter speed that you can set your camera to before switching to "bulb". If your camera goes higher, then you can go higher. And trust me it would be nice to do longer exposures, so you can have fewer photos to work with. I just haven't put the time into exploring other options as of yet. Again, remember that there will be a noise threshold for longer shutter speeds. Some things that might be worth exploring are intervalometers if there are any available for your camera, or tethering to a computer. I've tried intervalometers with so-so luck but haven't been able to perfect it yet. With my cameras and the intervalometers that I've used, the shortest interval between shots I'm able to get is 3 seconds, which to me is way too long, especially when facing the east or west when stars "move" the fastest. If I become more successful with this method or any other method I discover, I'll be sure to update this section.
One thing to avoid when photographing star trails: pointing your camera at an airport!
Most of my star trails shots I’ve rendered using Image Stacker. It is a pretty efficient piece of software for combining your images, and it also has a few other blending options such as stacking, or averaging photos to reduce noise........ It costs $17 for the full version.
To start, you just click the "Add Images" button and choose your images. Sometimes I change the name of the output file. Under "Image Blending Options", choose "Brighten (Use Brightest Pixel)". Once you have them loaded into the software and named the file, you just click "Start" and it will begin combining all of your images.
This is what it looks like when it is processing:
Recently I’ve also discovered some freeware that could potentially become my new software of choice for combining the photos. It’s called startrails.exe It was created for the soul purpose of combining images for star trails. It will also build a time-lapse video of your photos , which I have not tried yet.
To start, just click "File >> Open Images" and choose your images. Then choose "Build >> Startrails", and it will begin combining all of your images.
Here is what it looks like when it is processing. Notice that it will continually show you the photo as it is being rendered. That's a neat feature.
If anyone uses other software, I'd love to hear about it as well.
There you have it! ... I hope you found this guide useful. As I had said above, I encourage feedback so that I can improve, and please feel free to email me or comment below with any other questions or comments. Enjoy shooting your star trails, and please send me a copy of your photo if you try. If I get enough, I'll create a gallery with others' names and photos and link to it from here.
And remember the most important lesson of all in photography: Have Fun! You are going to make mistakes. Don’t worry, everyone does; just remember that each mistake you make leads you to becoming a better photographer!
Over the past few weeks I've received an unusually large amount of emails that I haven't had the opportunity to answer. Thanks so much for your patience as I work through each of them to answer them to the best of my ability. Frankly I'm excited to see so many people with interest in pointing your cameras at the sky, and I'm certainly happy help out, and share the joy!
expensive stuff. :)
It costs you nothing and it supports my photography.
Let's hope it gets good ones soon!