This is an article I have been meaning to write for years, because whenever I post a star trail photo, I almost always get questions on how to create these images.
Of all of the different types of photography I have done over the years, star trails are the easiest.
The great thing about doing star trails on color film is that you can “set it and forget it,” and then send the film off to be processed. With digital star trails, you need to set up a timer to take many (sometimes hundreds) of images at regular intervals and then stack them all together in Photoshop or other astrophotography software to create the final image.
Both of my boys have always been interested in space, and we thought this would be a great family hobby.
And it has been! In fact, my oldest son is now an astrophysics major in college.
Our stargazing outings usually begin around 10 p.m., with my son setting up the telescope and me setting up my cameras. I’ll start an exposure, and while the shutter is open, we will look at various celestial objects through the telescope.
So, let me tell you how I do it!
What’s in My Bag
At least two cameras
I prefer completely mechanical cameras so that I don’t have to worry about batteries dying during the middle of an exposure.
The best night to stargaze or shoot star trails is the night of the new moon, because you don’t have to worry about the moon spoiling your shot or outshining all of the other celestial objects and stars.
If you need to go on a night when the moon will be out at all, wait at least an hour after it sets before trying star trails. If you don’t, the moon will make the image look like a sunset.
Is your location safe—safe from wildlife and safe to remain late at night? If you’re in a public park, is there a curfew?
If you think you may want to shoot on private land, be sure to obtain permission.
A Few Tips for Shooting Star Trails
Load your film at home before you head out. It’s much easier to do it indoors with good light than outdoors in the dark and probably cold weather.
I take at least two cameras with me because each exposure is at least 30 minutes, but usually 60-120 minutes. If I have two or more cameras going at once, I can come away from a star trail expedition with at least two to four images.
Choose your site and composition carefully. Hopefully, you’ve found a dark location with something interesting to look at. Unfortunately, living in Iowa, the darkest locations are out in the middle of a cornfield.
It’s nice to have something interesting in the foreground, but it isn’t absolutely necessary. I’ve used leafless trees or simply the horizon.
Also, consider how you want your start trails to look. Do you want them to circle around Polaris, or do you want them to streak across the sky?
I like to use a “normal” focal length (50mm for 35mm film or 75-80mm for medium format film).
You can also use a wide angle or telephoto lens, but any lens you choose will affect your exposure and the look of your image.
If you choose a wide-angle lens, you can shoot it wide open. If you choose a telephoto lens (anything above 200mm), you may want to stop down a couple of stops because the magnification will be too much, and the trails will be wider than you might wish.
You will also see fewer trails because of the smaller angle of view.
I think what makes star trails so beautiful and interesting to look at is the magnitude of stars in a large sky and the illusion of movement they create with a stationary foreground or horizon. A telephoto lens won’t give you that perspective.
Choosing a Color Film Stock and Reciprocity Failure
When doing long exposures on film, I like to choose a slower speed film, usually ISO 100 or less.
The longer your film is exposed to light, the more pronounced the grain will be when the film is developed. That is slightly minimized when you use a slower film with smaller grain to begin with.
For star trails on color film, I like slide film the best because the colors are so vivid.
But be warned, long exposures with any film, but especially slide film, will cause distinct color shifts, which is part of reciprocity failure.
When making star trails or any long exposure on film, it’s good to have a basic understanding of reciprocity failure of film. It’s important to understand that the longer your film is exposed to light, the less light sensitive it becomes.
With prolonged exposure, the dye layers will absorb light unevenly. The dark night sky can become a bright magenta. For me, this is one of the beauties of shooting long exposures with color film.
Focus your lens at infinity. To guarantee that your focus doesn’t shift during the long exposure, you can use gaffer tape to secure the focus ring.
If you’re including something like a building or other object of interest in the foreground, be sure to make that focus priority.
Open your lens to its widest aperture. I like to use a lens with at least an aperture of f/2.0. Set your shutter speed to B (bulb). Attach your cable release.
If your camera allows it. Use your mirror lockup function to avoid any camera shake.
Cover your eyepiece with a viewfinder cap (these can be purchased separately for some cameras, and some cameras like the Contax 645 have a built-in viewfinder cover) or a piece of gaffer tape.
When the shutter is open for a long time, light can leak in through the viewfinder. I think it’s a fairly rare occurrence, but this is an easy fix or precaution to take.
If you use a camera that requires batteries, be sure to bring extra batteries or use a battery grip to extend your battery life.
If you have a way to attach your camera to a DC-power car adapter, that would also be a good way to prevent power loss.
Exposure time will vary depending on your lens focal length and how close you are aiming at Polaris. At minimum, you will need at least a 20-30-minute exposure to show any movement.
If you are shooting with a wide-angle lens or including Polaris in your frame, you’ll need a longer exposure—at least 60-90 minutes.
With a longer lens or a composition that does not include the North Star, you could have shorter exposure times with longer trails.
Taking the Shot
Push the shutter button on your cable release and lock it into place.
Start your timer.
Go take a nap, read a book, look through the telescope while you wait for your long exposure to finish.
Repeat for as long as you can stay out or awake or until the sun comes up.
Which Direction to Point Your Camera
When choosing which direction to point your camera be sure to take into consideration which direction the largest town or city is from your location.
Point your camera in the opposite direction unless you want to include the glow that the city lights will create in your image.
You may not be able to see the glow with your naked eye, but with a long exposure, that glow will be very prominent.
Sometimes that glow adds interest to an image, but often it is undesirable.
One other thing you can do that is similar to digital star trails is that you can take more than one long exposure and stack them together later in Photoshop.
I don’t consider this “cheating” because you could achieve the same effect in the darkroom, just with a lot more work!
A Little More Information
What I love about star trails is that they are the visual representation of the passage of time.
One of the first things that struck me when I looked at my first star trails was just how many stars were recorded. When the images are magnified to 100% or greater, even more stars are visible, though much dimmer.
And while it is possible to see the different colors of stars with the naked eye, the colors recorded on film (especially slide film) are magnificent. (Stars have different colors because of their temperature.)
Understanding Star Movement
It’s important to remember that the stars appear stationary (even though they are moving, too), and we are the ones moving.
If you want to have the longest star trails in the shortest amount of time, point your lens toward a horizon. If you want your star trails to appear to move in a circle, point your lens at Polaris.
If you don’t know how to use the Big Dipper to find the North Star, use the Star Map app.
This app is really fun. Hold your iPhone or iPad up to the sky, and the app will tell you what stars, planets, galaxies, and other celestial bodies are out there. Move the device, and the app will move the star map to keep up.
Note, that if you include Polaris in your image, you’ll need to have a significantly longer exposure to show much movement compared to an image that includes the horizon.
To help you understand why that is, imagine the sky as a giant sphere and the earth in the center of that sphere.
Then, imagine that the sky sphere is spinning on an axis that goes right through Polaris.
The stars spinning around Polaris will appear to travel much shorter distances than the stars closer to your horizon in the same amount of time because the space at the top of the sphere is smaller than the space nearer to the horizon.
Here’s another way to think about it: Think of a spinning basketball on your finger.
If you put a dot close to your finger or at the top of the ball near the axis that your finger creates, that dot will create a circle while the ball spins.
If you put a dot farther down on the ball, it will also create a circle while it spins.
The circle near the axis will be smaller than the circle farther away from the axis. This is why star trails that include the North Star appear so short compared to star trails that are farther away from the North Star.
Where to Go From Here?
There are still lots of things I want to try with star trails on color film. I want to try light painting something in the foreground with the trailing stars in the sky. I’d also like to try even longer exposures than I have done already.
While researching this article, I learned that some photographers like to stop down to f/5.6 to f/11 to reduce the light pollution glow. I’d like to try this for myself to see if it works and if the star trails are dimmed at all.
Finally, I am really inspired by an amazing photographer named Jason De Frietas who has created some phenomenal film images of the Milky Way using a tracker similar to the one on our telescope that compensates for the earth’s movement when looking through a telescope or making a long exposure without showing movement.
I would love to give the tracker a try with one of my film cameras.
Star trails are some of the most fun and most beautiful images you can create on color film.
The process is fairly simple, but it requires some advance planning and a few pieces of special equipment such as a tripod and a cable release. It’s also time-consuming, and one outing may only produce a couple of images.
Under the right conditions with the right gear and a little forethought, you can create a timeless image of the passage of time.