The above image, “Star Trails Above Echo Lake,” was captured this past September in Acadia National Park. It is comprised of 85 individual pinpoint star images, shot over about a 45 minute period, that have been stacked and blended in Photoshop. I have received many questions on how it was done so I thought I would write about it here. I am going to split this into two segments, the first on how to capture the images and the second on processing and stacking the images. I used no special equipment, other than a cable release with a lock for the shutter button, to capture the images. Any DSLR or Mirrorless camera capable of operating in a manual mode can do this. I used no special software to stack and blend the images other than Lightroom and Photoshop. Any version of either program will do this. With that said let’s take some pictures.
Capturing the Images
The first step to getting the best images for star trails is timing. You will need to select a clear, moonless night to shoot. A few nights before or after the New Moon will work perfectly. There are numerous websites and smart phone apps to help you select the proper night. Keep an eye on weather forecasts for clear, cloudless skies. Very dark skies are important too and you should plan to start shooting about an hour and a half after sunset. Look for a good view to the North and keep your foreground in mind. You can use the reflections on a lake or a mountain landscape or trees to frame the view of the sky. Round star trails are easier to achieve if you can place The North Star, or Polaris near the center of your composition. There are also numerous apps to help find Polaris but it is the last star on the end of the handle of The Little Dipper. The camera must be set up on a sturdy tripod.
Camera settings are typical for pinpoint star photography. With a very dark sky start with ISO 3200 f2.8 and 30 seconds using the widest angle lens you own. I usually use a 10mm lens on a crop sensor body and 16mm on a full frame camera. If you don’t own a lens that will open up to 2.8 then f4 will work you just may have to increase the ISO to 6400. Adjust the exposure until you are happy with the way they look. It can be very helpful to arrive at your shooting location before dark to focus the camera properly. I will find a distant object to focus on. Anything over a couple of hundred feet will work such as a distant mountain top or a cell or TV/radio tower. If you cannot arrive before dark you may be able to use your camera’s “live view” and focus on a particularly bright star or planet. You may have to turn off the camera’s “Exposure Simulation” function for this to work properly. Once you have found a star or planet on the live view screen it will probably be very helpful to zoom in on it, not with the lens but using the electronic zoom on the live view screen. I find that zooming in to 10X allows me to focus very precisely. Shoot a couple of test frames to verify the exposure and focus. Zooming in on the captured images will help verify focus. You want to see pinpoints or very short dashes but you don’t want to see “snowballs”!
Actually capturing the images couldn’t be simpler. Set the camera for continuous capture just as if you were shooting birds in flight or a sporting event. With the locking cable release attached fire the shutter release, lock the switch down and walk away. Now the waiting begins! The longer you let the camera run the more images it captures and the more images it captures the longer the star trails will be in the final image. I captured the above images over 45 minutes but you could go a half hour or an hour or more if you have time. It’s best to just leave the camera alone and let it do its thing. Stay well away from it so you don’t accidently bump it or the tripod. At the end of the allotted time period unlock the cable release and let the camera finish out its last exposure. Now pack up and go home, you’re probably pretty tired!
Next time; Processing and stacking the captured images.