6 minute read
How to Start Creating Star Trails
Framing the cosmos in the night sky is a challenge few photographers can ignore. Our tips on technique and gear are what you need to do it well
There are few things as spectacular in photography as a star trail – the cosmos smeared across the night sky as the Earth rotates on its axis. Framing this on camera can be a very satisfying technical challenge.
Creating star trails requires a long shutter speed to turn stars into streaks of light as they move across the night sky. The principle is the same as we would use for traffic trails, only on a much longer timescale to reflect the relatively slower movement of the stars, caused by the rotation of the Earth.
This type of astrophotography is quite technical, but not as difficult as you might first think once you’ve had time to digest and practice the techniques involved.
The conditions have to be just right for a star trail photograph to work. You’ll need dark skies away from light pollution (Blue Marble’s night map can help you here), and very little cloud coverage. Moonlight is useful to light up the surrounding landscape, though you’ll want to make sure you don’t have the moon itself in the frame, since this is much too bright for the long exposures we’ll be using.
You’ll need to photograph for a few hours in order to get long enough trails to fill the night sky, so make sure you take plenty of warm clothing, food, and water with you.
When it comes to photographic equipment, there are rather specific requirements. A good sturdy tripod is essential – something that won’t move as you’re making images. You’ll also need a wide-angle lens that can ideally deliver a fairly wide aperture. The 18mm end of the FUJINON XF18-55mmF2.8-4 R LM OIS is ideal.
We’ll be working with very long shutter speeds, which can consume a lot of battery power, so make sure you take plenty of spares with you. Even better is an accessory battery grip that lets you photograph with more than one battery at a time without having to stop to physically change over.
Last, a wired remote control is useful for photographing without wobbling the camera, but it’s not essential as we can also use a self-timer or the FUJIFILM Camera Remote app.
Using the Interval Timer
It’s absolutely possible to create star trails in a single long exposure: the longest shutter speed an X Series camera can handle is 60 minutes in bulb mode (marked by B on the shutter speed dial). This setting keeps the shutter open for as long as the shutter release button, or its remote-control equivalent, is held down. But ugly noise can creep into pictures made in this way, so we’re going to use a different method.
Using the camera’s interval timer, we’ll make a series of shorter exposures and merge these together in post-production to give us the finished star trail. To set this up, go to SHOOTING SETTING > INTERVAL TIMER SHOOTING in the camera’s menu. Set the lowest interval possible (one second) and set NUMBER OF TIMES to 100 frames (a good starting value).
Shutter Speeds and Apertures
Set the camera to manual exposure mode and choose a shutter speed of 30 secs (do this by selecting the T setting then using the rear control dial to choose the shutter speed). Making a hundred 30 sec frames, with one second between each one, will take a total of 51 minutes 40 seconds (50 minutes of exposure time + 100 seconds of pauses between frames).
Choose an aperture of F2.8 to F4 and focus on infinity. Focusing on the night sky is often very difficult, so pick another distant object to focus on instead, using manual focus mode, then leave this set as you point the camera back at the sky.
We’re nearly ready to begin making our image, but there’s one last important thing to do – turn off LONG EXPOSURE NR from the camera’s IMAGE QUALITY SETTING menu.
Long exposure noise reduction works by photographing a blank frame after the main exposure, but this second exposure lasts as long as the first and inserts a 30-second gap between each of the frames. Using this would give us dotted star trails instead of solid lines, since the Earth carries on moving when the camera is recording its blank frame.
Making Your Image
When you’re ready, start the exposure sequence by pressing the shutter release button on your remote control or FUJFIILM Camera Remote app. The camera will go about its business making 100 frames at the same exposure, and you can sit down and relax for the next 51 minutes 40 seconds.
If you want to extend this time in subsequent attempts, you can either lengthen the shutter speed (100 x 60 sec exposures would cover one hour 40 minutes) or photograph more frames (200 x 30 sec exposures would also cover one hour 40 minutes). Or both!
Once you have the frames from your star trails session, you’ll need to merge them to form the finished star trail. If you photographed RAW files, the first task will be to process all 100 images into JPEGs. Use the batch processing facility in your RAW processing software to do this. If you photographed JPEG files, just use what came off the camera.
There are many dedicated apps that can merge multiple frames to form star trail images – one example is StarStaX – but we’ll use the layer blending functionality in Photoshop to do this.
STEP 1: Open your JPEG frames as a single stack of layers in Photoshop by choosing File > Scripts > Load Files into Stack… from the menu. Click Browse… and choose all 100 files before clicking Open. After a little time, Photoshop will open an image containing 100 layers, each containing an individual image
STEP 2: If it’s not already visible, show the layers palette by choosing Window > Layers. Scroll to the bottom of the list of layers and click the second-to-last layer to select it. Set Blending Mode to Lighten using the drop-down menu in the layers palette
STEP 3: Right-click on the same layer and select Copy Layer Style
STEP 4: Select the remaining layers (clicking on one, then shift-clicking on another lets you select a range) before right-clicking again and choosing Paste Layer Style. All of the layers will inherit the blending mode, and the finished star trail should appear before your eyes
© Andy Noble
As we said at the start of this tutorial, creating star trails is a fairly technical exercise, but with practice and patience you’ll soon start to get a feeling for it and gain the confidence to make changes to the numbers and settings we’ve outlined here.