The process to photograph startrails with stacked images is a great skill to add to your bag – and as I found during the current Covid-19 lockdown it is something you can learn and practice from home. It requires no filters or other expensive kit so all you need is a camera that you have manual control over, a tripod, and a way of remotely firing the shutter. There are some very elaborate intervalometers out there, and I would imagine there are apps that allow you control from your phone, but I use an inexpensive Canon RS-60E3 remote switch which simply replicates the function of the shutter button on the camera.
General Principle of Startrail photography
There are basically two methods: single exposure, where the camera is left exposing on bulb mode for a long time; or ‘stacking’, where images are taken one after the other and then blended together on the computer. This article describes the latter method, using Starstax software.
The photograph featured above is actually 130 photographs that were taken one after the other and then processed with Starstax. I started the first one before it was properly dark hence the blue colour in the sky (and using a cool white balance temperature)
Camera Settings for Startrail stacks
Startrails using stacked images have to be exactly the same for the foreground. The only thing that should move is the earth so a solid tripod is essential. If there is any wind at all then you don’t want your camera strap attached as this acts like a very good ‘sail’ pulling the camera around. The settings then are as follows:
- As wide a lens as you have set to the largest aperture (smallest f Number) you can go to. This changes from lens to lens.
- ISO setting – you might want to experiment but between 800 and 1600 seems to be the favourite. The above was taken at ISO800 after a few nights experimenting with higher values. Remember that the general rule is that the image quality deteriorates as the ISO increases. See my article on ISO for more details.
- Autofocus OFF, focus set to infinity. If your camera doesn’t have a manual focus ring then put it in autofocus during the day, focus on a distant object (clouds or anything else that is as far away as possible), then put it to manual focus and don’t touch it.
- Whitebalance – this is personal preference to a certain extent, I used 3200 kelvin for the above shot which contributes to the blue accent.
- Exposure time – the example above was 30 seconds.
- Shooting mode set to to continuous (as soon as the 30 seconds is up it will stop and start taking the next one straight away)
- Note that Starstax cannot accept RAW files. You either need to shoot in JPEG, or convert all your RAW files into JPEG once you’re finished shooting. This does of course give you the option to bulk edit the RAW files to adjust things such as white balance for ultimate control. The shot above was shot in JPEG in the camera. See my article on RAW files if that’s of interest.
Startrail Stacking Method
Composition is key as per any other image. Star trails can be taken looking in any direction, but to get the circular effect you need to ensure that Polaris, the north star, features in your shot. As Polaris is directly in line with the earth’s poles it is the only one that doesn’t appear to move as the earth spins. There are plenty of articles on how to find the north star elsewhere so I wont repeat that here.
Get your composition sorted out during the day and leave the camera set up ready for when it gets dark. Try and avoid any bright spots such as streetlights if you can and if like me you were taking a photograph of your house think about which lights are on / curtains drawn, etc.
You’re all set – once it’s dark go and start the camera shooting. For the first few frames leave the lens cap ON – this will give you some black images that Starstax will need as reference shots later on. Then take the lens cap off and leave the camera doing its thing. I’d recommend starting the process just before it’s properly dark and leaving it for an hour and a half or so. This will give you 180 images and you can decide the best starting point later.
Processing the Startrail stacked images in Starstax
There are plenty of excellent tutorials on Starstax so I won’t go into a lot of detail here but the high level process is simple:
- Load your images – ‘File – Open Images’
- Load those dark frames you took – ‘File – Open Dark Frames’
- Select ‘Gap Filling’ in the tools
- Click the ‘Start Processing’ icon and watch the magic happen
- This will give you a finished JPEG which you can then go on to adjust further in Photoshop etc if you wish.
There are some other options and adjustments to try in Starstax of course but the above will give you some great results as a starting point.