I have a lasting memory of being sent into the garden as a lad, with my dad’s prized Rolleiflex 35mm SLR, and told to point it at the north star (Polaris) and keep the shutter open for an hour or so. Whether my father just wanted some quiet time, or thought it might inspire the astrophotographer in me, I don’t know and he can’t remember! That night, searching the clear starry sky and shivering away waiting for the camera to do its thing, has stayed with me. I don’t think I got a single successful shot back then. Fortunately, things have become a lot easier, but no warmer!
There are a few ways to make great star trails images, the technique I’m covering here involves taking a series of exposures then blending them together in a piece of clever software called StarStax.
Plan the scene
It’s worth having a plan for your scene with some foreground interest. In my example, I chose an ancient Quiot burial chamber. My thought was the connection between the old, death and remembrance with stars eternally turning above had a good narrative about it. It also had the benefit of being out on the moors away from light pollution.
Capture a series of photographs
I used PhotoPills to give me an idea of how many exposures I would need to make decent trails then I put the camera in interval mode and simply pressed go. I wanted the stars to trail so I left the shutter open for 30 seconds each time. Had I wanted no trail with the Sony A7riii and a 20mm lens it would have been more like 10 seconds max. I only had time for 150 exposures for this shot but the more the merrier. Do carefully check your lens hasn’t fogged up periodically though (that may have happened to me before!) and don’t worry too much if a frame is spoilt by headlights, for example, you can always leave that frame out later. The added benefit of shooting so many frames is you can also make a timelapse out of it. This isn’t a quick job so be prepared, camp chair, warm clothes, snacks and a hot drink. You can either star gaze or listen to inspirational podcasts. Have spare batteries in your pocket just in case, particularly when it’s very cold. When you’ve got them back on your computer make sure you have them as a numerical series i.e. file names 1,2,3,4 etc. If exporting from Lightroom this can be done in the export settings.
Blend in StarStax
StarStax is a free piece of software (but please consider supporting the developer if you like it) that can be found here. When you’ve opened it up drag and drop your set of images. Don’t worry if they don’t look like much at the moment, the magic is just about to happen! On the right-hand side make sure ‘blend by lighten’ is selected. This will bring all the lighter parts together which is what we want for stars and also has the benefit of providing foreground interest if there is any residual light pollution knocking around. All you have to do then is click the button on the top left that looks like pucks stacked on top of each other. I think this is the coolest bit as you get to see the image come together in real-time and your star trails extend in an arc.
Save your final image as a .tiff file so you can still make the most of adjustments and bring back into your editing software to make any adjustments you might want. And there you have it – a beautiful star trail image, easy when you know-how and shows the night sky in a unique way that is not possible with the naked eye. PhotoPills have done a brilliant handout that goes through how to set up your star trail shots to get different effects. That can be downloaded here.