Star trails are the continuous paths of the stars, produced during long-exposure photographs. The camera captures apparent motion of the stars as night passes. The resulting star trail image captures the nightly movement of the earth in relationship to the stars.
Star trails reflect the Earth’s rotation. The Earth rotates full circle in a period of about 23 hours and 56 minutes. Many photographers use a technique of shooting multiple, shorter length, time exposures and stack them during post-production. 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.
Where you point the camera in the night sky will determine the shape of the star trails in your final image. Pointing your camera at the North Star (Polaris), will give concentric circle star trails. Other compositions can produce arc shaped star trails and pointing the camera facing west will create a falling star look.
While the length of the star trail will be dependent upon whether you spend only a few minutes making exposures or are out shooting all night. If you want star circles, you'll need to be out shooting all night and then stack the images.
Many of the photographs that are taken of star trails are captured using wide-angle lenses, so interesting 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. The image to the right was shot as an HDR image. A "blue hour" image is shot for the foreground and a one hour exposure shot for the stars, the two are blended in post. This image is made with natural lighting.
This image was done with Low Level Lighting. This method of lighting the landscape for landscape astrophotography is more uniform and controllable and has less light pollution than light painting. Using a constant dim light, typically from LED light panels mounted on tripods or light stands.
Low level lighting can accentuate landscape features at night and demonstrate the features even better than during the day. The photographer determines the angle and character of the light. This gives hilights and texture to the feature.
This image of Sid and Charlie is in the San Rafael Swell. A one hour exposure. Camera settings are adjusted for the low level lighting and one hour exposure. Nikon D750, F/5.6, ISO 125, 1 hr ,Tokina 16-28mm, f/2.8, 19mm
Setting up th camera depends on the exposure time. Set the camera to bulb mode. Use an intervalometer to control the shutter time. Set the ISO for proper exposure. Make sure you turn on the long exposure noise reduction. Your camera’s on-board computer will take a 2nd black exposure. This is to compare and eliminate hot/noisy pixels from the image. The black exposure will take another 30-minutes to 1-hour,
depending on the exposure you chose.
You can pack away your camera and tripod and go to
your next location while it processes —just don’t shut off
This image was shot at Arches National Park. Using low level lighting and the Royce Bair recipe for star trails. I highly suggest purchasing Royce's ebook for night photography. It is 149 pages for $20.
A short list of camera equipment for Star Trails Photography
Tripod: A well made and sturdy tripod is very important for star trail photography. I use Field Optics BT PRECISION BOWL TOP. Great tripod for only $500. Cheap tripods usually shake and vibrate easily, making your pictures blurry.
Camera with Manual Mode Functionality: “M” or manual camera mode means you can manually, and independently adjust the Aperture, ISO, and Exposure settings on the camera.
Camera Timer / Intervalometer: A timer is essential for star trail photography. A camera timer / intervalometer allows you to take multiple, long exposure photos, one after another. Most cameras only allow a 30 second maximum exposure time.
Fully Charged Batteries: Three to five fully charged batteries. You will be shooting over a time ranging from 30 minutes to 3 hours.
Wide Angle Lens (Optional): Star trail photography is much more forgiving than Milky Way photography.
A “fast” ( number under the “f” is small ) lens is still recommended.