Kevin Ferrioli shares his favourite Dorset locations and the best time of year to capture great images.
Astrophotography Mary McIntyre
My journey to become an astronomy communicator and astrophotographer
I have loved looking at the night since I was a small child, but got really serious about astronomy in 2010 when I began to study for some formal astronomy qualifications.
Part of my coursework for one of my courses involved lunar photography and that’s when my astrophotography journey began. I love taking photos of absolutely everything in the night sky, but one of my favourite things to do is star trails photography.
Star Trails Photography
Star trails images are very striking and have wide appeal, even to people with no interest in astronomy. These long exposure photos appear to show the movement of the stars but what we’re actually capturing is Earth’s rotation. Star trails photography is relatively simple and it can be done with very inexpensive equipment. Although it can be adapted to work in a light polluted location, if you do it from a dark sky site you will be amazed at just how many faint stars you capture.
12 hour star trail - Mary McIntyre
Top Tips - Equipment Needed
- Camera - all of my star trails photos have been taken with a Canon 1100D DSLR camera which is now ten years old. For years I just used the 18-55mm kit lens and now I use a 10-18mm wide angled lens, but you can use any lens you have. You can also use a bridge camera or any camera that can do exposures of about 15 seconds or more.
- Tripod – you need to keep the camera very still during the imaging session so a tripod is essential. You don’t need a high-end tripod but use one that has a hook underneath so you can hang something heavy under it to stabilise it.
- Remote shutter cable – this allows you to do the entire imaging run without touching the camera. I use the low cost unbranded ones that you can pick up for around £10.
Shooting the Images
- Focusing the camera - the only difficult part of star trails photography is getting the focus right. In the dark your camera’s automatic focus won’t work properly so you need to set the lens to manual focus. Point your camera at the brightest star or planet you can see, then use the live view screen and zoom in on the star. Adjust the focusing ring until the star is a tiny point.
- Choose your framing - from here in the UK, if we point the camera towards the North we will capture the beautiful concentric rings of star movement with the almost stationary Pole Star “Polaris” at the centre. If you point your camera towards the East, South or West, you will get a very different but equally beautiful image. See below for a comparison. It’s also great to have some foreground interest to give context. This could be a tree, a windmill or anything that will add interest.
- Set the camera to around ISO-800/ISO-1600. With budget or old cameras like mine, going higher than this introduces a lot of noise to the image but can also bleach out the star colour. Set the lens to around f/3.5 or lower. This will allow more light to get onto the camera sensor.
- Doing one single long exposure image does not produce great results. It’s far better to take lots of shorter exposures and use a simple app to stack the images together. So, set the shutter speed to 30 seconds, make sure your camera is set to “continuous” then press and lock the remote shutter cable. The camera will then keep taking 30 second exposures until you stop it. You don’t need to image for hours like I often do; anything from 30 minutes upwards is fine.
- I always shoot star trails in jpeg; this is for a couple of reasons. Firstly the write-to-card speed is much faster resulting fewer gaps in the stack. Secondly raw files take up lots more space on the memory card, then to use the stacking software they have to be converted into TIFFs files which are even bigger! I find it’s easier to just use the highest quality jpegs and the results are fine.
Stacking the Images
There is a free star trails app called StarStaX. This app works on Windows, Mac and Linux and it’s very simple to use.
- Open StarStaX
- Drag and drop your images into the software. Make sure you’ve selected “gap filling” on the right side, then click the “start processing” button at the top.
- Once the stacking is complete, save the image.
Star trails images don’t usually need much processing, but you can make small tweaks using your favourite imaging processing software. I like to use another excellent free programme called Fast Stone Image Viewer. You may want to increase the contrast a bit and boost the colour saturation to bring out the star colour. Remember that less is more when it comes to image processing. It’s also helpful to de-noise the image if your camera is old like mine and Fast Stone’s de-noise function is excellent.
If you want a more detailed guide to star trails photography, which also includes instructions on how to create a star trails timelapse video and contains all of the download links for the software I use, you can download my star trails photography guide.