Photographing Star Trails is a unique way to capture the night sky in a photograph. A star trail occurs when you photograph the stars over a long period of time, from minutes to hours. We spoke with two photographers—Deborah Sandidge and Harold Davis—to find out their techniques and tips for great star trail images.
Many photographers who photograph star trails use a technique of shooting multiple shorter length time exposures and stack them during post-production using Adobe Photoshop or another program that will allow you to stack multiple files into one photograph. This allows them to produce a more dramatic effect in the final image. Another reason to use shorter exposures is to reduce the occurrence of noise that can show up in an image captured during long exposure shooting. In addition to shooting multiple images and stacking them, using as low an ISO as possible will also limit noise in the final image.
To capture the maximum amount of light put out by a faint light source such as stars, you’re going to need to use a fast aperture. Harold explains: “Let’s say that the right exposure to capture starlight is f/2.8 at ISO 400 for two minutes. The comparable exposure value at f/22 and ISO 400 would be about two hours (since each full f/stop lets in half the light of the previous f/stop). But I often want to capture starlight for longer periods, such as an entire night, to produce images with complete star circles. These star circle images can usually only be accomplished via stacking.”
To simplify the process of shooting the individual shots every few minutes, Deborah sets her camera’s interval timer to make the consecutive images. The built-in interval timer can be found under the shooting menu. (Check your camera’s manual to see if your specific model incorporates this feature. —Editor)
Deborah says, “I stack stars because it gives me more flexibility with the outcome of an image.” She creates most of her star trail photographs using an exposure time of 30 seconds; making a number of photographs over the course of three-quarters of an hour or so. She then stacks these images which composites the images using Statistics, in Adobe Photoshop.
“I will often composite a foreground using HDR to blend with the final image,” says Deborah. “This helps prevent any detail from being lost in the highlight and shadow areas of a foreground area that isn’t in silhouette.”
The fullness of the star trail stacking will be dependent upon whether you spend only a few minutes making exposures or are out shooting all night.
Where you point the camera in the night sky will determine the shape of the star trails in your final image. For instance, if you center your composition on the North Star (Polaris), you’ll end up with concentric circle star trails. Other compositions can produce arc shaped star trails. In her image of star trails photographed at the Indian River Lagoon (image #3), Deborah positioned the camera facing west to create a “falling star” look.
Many of the photographs that are taken of star trails are captured using wide-angle lenses, so interesting “terrestrial” foreground elements can be incorporated into the composition. Some of these foreground subjects will make ideal silhouettes, while others would benefit from a little exposure (natural or man-made).
Harold notes, “In particular, when I’m trying to capture circular star trails, I enjoy using my 10.5mm Fisheye lens because using an extreme wide-angle lens helps to amplify the curvature of the motion of the stars relative to the earth.” He cautions: “Bear in mind that the foreground elements in your composition are extremely important—perhaps more so than the night sky in the background.”
There are a variety of techniques that can be used to light the foreground for a star trail image, including making exposures at different settings and combining them as an HDR image, light painting the foreground using a flashlight or similar constant light source, and painting with light using a Speedlight. For Speedlight light painting, you manually “pop” the Speedlight's Flash button to fire it, doing so multiple times, to spread the light across the entire area to be illuminated, while the camera’s shutter speed is set to BULB.
It is always a good idea to make a few exposures, especially if you’re light painting to fill in the foreground area with visible detail. “Be sure to go easy on the light painting or it will look unnatural,” says Harold. “Also, keep the light source in motion at all times so you don’t create ‘hot’ spots,” he adds.
Keep in mind that the Moon will be very bright relative to the stars. Including the Moon in an image along with star trails may necessitate you taking addition exposures specifically for the Moon and compositing them into the final image. This was the case with Harold’s image of Pfeiffer Big Sur Beach (image #7). Because the Moon was visible in the sky, in a position that would make it visible in his composition, Harold had to decide which subjects were the most important. His solution was judicious placement of the Moon in the frame, allowing it to “blow out the highlights” so that the starry sky would be correctly exposed.
UFOs in your star trails
“When you do take star trail images, don’t be surprised if you see other light trails winging across the sky in your photos,” says Harold. “Many times, my star trail photos include airplane and helicopter lights as well as light trails from satellites,” he explains. Oftentimes, these trails of light will be in a completely different direction than the star trails.
Tips to Making Better Star Trail Photographs
Bring a flashlight with you, so you can easily see the camera to change settings while shooting at night. If you’re planning on photographing the sky all night, bring a chair so you’ll be comfortable.
Use a compass and star charts to help you determine where to place the camera so you get the type of star trail movement across the photograph that you want.
Place the camera on a steady tripod, and use a cable release to “snap” the pictures, to keep from causing vibrations during the long exposures.
Include foreground elements in your composition for a more interesting photograph.
Lock the focus.
Use a low ISO to keep noise to a minimum.
Use shorter exposures when possible, even though you may end up making more images to stack together, as this will also keep noise to a minimum.
Turn ON the camera’s Long Exposure Noise Reduction feature.
Shoot test exposures to see exactly what f/stop and shutter speed (or length of time with the camera set on BULB) will produce a well-exposed image. Use the camera’s histogram to check exposures.
Close the eyepiece shutter to keep stray light from entering via eyepiece.
Shoot RAW (NEF) so you can easily make adjustments in post-production.
Turn OFF the LCD display to conserve battery power.