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HOW TO TAKE STAR TRAIL PHOTOS
Star-trails can look exceptional when done properly. The idea is usually to capture a series of circular trails that rotate around Polaris (the North Star). This can be achieved in one of two ways: photo-stacking or a single, very long-exposure image. At times, a subject cannot be viewed from the direction of north, or does not look appealing when viewed from that angle, so you may have to settle for partial trails.
Whichever method you decide to adopt, you will need a tripod to ensure that you capture the exact same image and keep it blur-free. Photo-stacking involves taking multiple images of the same scene and ‘stack’ them together into a single picture using computer software. Since the only difference in each of the images should be the position of the stars (which appear to rotate around Polaris), a star-trail will appear in the processed picture. Many cameras now have built-in functionality for what is essentially time-lapse photography, allowing you to set the controls to automatically take photos at specific intervals. For unbroken trails, ensure that the interval between frames is small.
Taking a single image saves time with stacking photos and allows you to see the finished image instantly, but it does have associated difficulties. Before taking your single image, which requires a shutter release cable, you need to check all settings are perfect and take a test image at very high ISO. Failing to do these things can lead to the frustrating outcome of producing a poorly focused image, a poorly lit image, or an image that omits the North Star as a center-point of the trails. Test shots are very important, especially considering that producing an acceptable star trail usually takes over an hour. Depending on the temperature outside, and your camera model, batteries may deplete from a single star-trail, limiting how many chances you get to capture a scene.
Regardless of which method you wish to employ, you should find the following checklists helpful in achieving your star-trail photograph.
- Find a strong subject that you would you to capture, or at least something slightly interesting.
- Check the light source(s) around the image at night, as some places are lit in such ways that make them virtually impossible to photograph without overexposing (too much light) the shot or needing to apply hours of laborious post-processing.
- Use a compass or phone app to locate north and assess how your subject looks when viewed from south looking north. If it looks boring then find a new subject.
- You need a tripod or at the very least, a stable surface to capture your image with absolutely no movement. A shutter release allows you to open the shutter with no vibrations. If your camera has a mirror lock-up function then you can also use this to remove the minute vibrations that can occur when the shutter slaps up.
- Clean all of your gear before going out into the night, and have a blower with you to use throughout the shoot. Dust particles always end up on your lens during a long shoot, so every few minutes you can blow the glass from a side angle without interfering with the image creation.
- Bring a torch to help you view your camera settings, find a focus point in the dark, and to ‘light-paint’ objects that are very shadowy and likely to appear under-exposed (dark). Remember that anything bright in the field of view will appear in a long exposure (which is why star-trails are possible), but dark things moving, like ourselves, will not appear unless they somehow reflect lots of light. This is why it is ok to be in the field of view during long-exposure photography, as long as you do not spend too much time in one position. When using a torch to paint in light on an object, make sure the torch always faces away from the lens and do not settle the beam on any area – keep it slowly panning around.
- Do not focus on the foreground. The stras need to be clear, so either use the short-hand rule of focusing one third of the way into your scene, focus to infinity, or preferably use a hyperfocal distance chart to exactly calculate how to include the largest possible area into the focus plane.
- If you arrive before dark and set up early, you can avoid the need for light-painting by capturing the same image both in the light (foreground) and dark (stars); allowing you to blend the images in post-production so that your final photograph has a star-trail with the well-lit foreground.
- Remember that light pollution will leak into your image. Shooting near a city can leave colour casts on the horizon. Before releasing the shutter, close the eye-view shutter to prevent any light from the rear from leaking into the sensor chamber.
- Bring extra batteries. If shooting on a cold night, try to keep your batteries near your body to keep them warm, or you may find they lose power faster.
- Shoot your test shots at high ISO (high sensor sensitivity), but remember to take your actual shots at lower ISO to prevent graininess.
- When using wider angles (such as 18mm), remember that trails will take more time to appear as long trails of light, as compared to zooming to say, 50mm. This makes sense when you think about it as pure magnification.
- Be aware of moon phases, as a half or full moon in the sky can weaken the visibility of stars and ruin a shot if it enters the field of view. On the bright side, some moonlight can be perfect for avoiding very dark areas in the scene that would usually require light-painting.
- Keep trying! You cannot always walk away with perfect star-trails. Taking a good image usually requires both practice and patience, and star-trail photography is no different.