Star trails photography
Night photography is an interesting alternative to the usual daytime images. There are various things you can try, including night portraits in cities where there is ambient light (see some of my fashion photography, for example). If you are a landscape photographer then star trails are a fun thing to have a go at. Yes, you can photograph the stars standing still as part of a landscape image. However, star trails can also add fascinating patterns to your night skies.
Night photography tends to mean long exposures anyway. If you photograph a starry sky for more than about 30 seconds then you will find that your stars have already moved and you are beginning to get some blur. Unless you are willing to shoot at high ISOs and with a wide aperture, you will find it difficult to keep the stars completely sharp and bright as your shutter will need to be open too long.
There are 2 main ways of doing star trails. The first is to do one very long exposure, keeping the shutter open for minutes at a time. This can have the advantage that you won’t have any chance of getting any gaps in your star trails. It also means that you have fewer files for processing later. There are a few potential drawbacks, however. Firstly, if there are other light sources in the frame it can be harder to balance the exposure and not end up with over-exposed parts of the image. Secondly, there is possibly a marginally higher chance of getting hot pixels. This can happen with method 2 anyway.
This image on the left was taken as a single exposure of around 12 minutes, f/7.1, ISO 1600. Unfortunately there was a bit of moisture developing on the lens, hence the marks around the lighthouse!
The second method involves taking multiple images and blending them together later using software. This has the obvious disadvantage of creating a very large number of files to store and work with. In its favour, you can also use these images to create time lapse videos. You may find it easier to get a more balanced overall exposure. Additionally, if a plane flies right through the middle of the image then you could simply cut that one file out of your final processing. That way, you don’t have streaks running in directions you don’t want them. This is, of course, personal taste. You may choose to keep the light trails from planes or passing vehicles in your image as well.
If you use method 2 then you will need to combine your files on your computer. There are various ways of doing this. One of the easiest is using Star Trails software. There are probably various reasonable programmes out there, but the one I use can be found here. Alternatively, you could combine your images as layers in Photoshop or a similar editing programme. I prefer the dedicated software as it demands less effort!
The technical stuff – camera settings
You will find various different approaches to star trails photography depending on whose articles you read. Some will say that you should keep your ISO as low as possible for the best image quality. Others insist that you must use as wide an aperture as possible to let in the most light. This all depends on what kind of final image you are after and how good your camera is at higher ISO settings. Modern cameras often have very little noise even at quite high ISOs and you can reduce it further or even eliminate it completely in post-production. So, it is not a hard and fast rule that you must stick to ISO 100 or 200. In fact, if you want to see more stars and/or you want to work at a smaller aperture then a higher ISO can work very well.
Using a wide aperture seems to make sense. It is dark, so you need to let as much light in as you can get. However, one problem with very wide apertures is lack of depth of field. If you are not simply photographing the sky but including some interesting foreground as well, then a very wide aperture will result in very little of the image being in focus. Yes, the wider the angle of your lens, the wider the aperture you can get away with, but shooting at f/1.8, for example, is unlikely to give you great results for your foreground and sky at the same time.
One thing is for certain – you will need to be shooting in Manual mode so that you can adjust the aperture, ISO and shutter speed yourself. You will normally have to do a test shot or two before setting off your series of shots to ensure that you are getting the exposure you are after. I normally aim for an exposure time of around 20-30 seconds. If you go longer than this then you can’t really use the images on their own as the stars will be blurring. Recently, I’ve been shooting with the ISO around 1000-1600. I find that there isn’t too much noise and it also brings out some of the less bright stars and colours a little more. As I like to include some landscape in the image, I tend to shoot around f/5 to give a little more depth of field. As I am using an ultra-wide lens, this means that I can get most of the image sharp. Play around with the settings in various combinations until you get what you are after. My settings may not suit you!
This is the tricky part. Focussing in the dark is not easy. Your autofocus won’t work unless there is a reasonable amount of light present. If there is enough light for your autofocus, then chances are that there is too much light pollution for you to get a good star trails photo! This means that you will have to focus manually. Manual focus frightens some people, but you don’t need to be fearful of it. Switch off your autofocus and use your focus guide on your lens. You may need a torch to help with this (I use the light created by my phone). You will want to set it around the infinity symbol, possibly a tiny fraction under to ensure you aren’t focussing beyond your landscape. Shoot a test image and adjust the focus if need be.
You may find that shining a torch on part of the landscape is enough to allow your camera to autofocus on it. You can then switch to manual before taking the shot to lock the focus. Alternatively, if it is dark but not pitch black, you could try viewing in live-view at a high ISO and focussing manually zoomed in to the image.
Yes, there is a little bit of guesswork involved and some trial and error. This shouldn’t frighten you as you can simply delete any images that are no good and try again! Get to know your camera and your lenses as well as you can so that you can judge the setting by eye as far as possible, then adjust as needed.
Where is the best place to try star trails photography?
Star trails are easier to shoot at locations where there is little light pollution. So, head out into the countryside if you can. The coast can sometimes work well too. Wherever you go, make sure that you are safe. Take a torch with you just in case so that you can find your way around ok. Look for locations with something you can include in the foreground as well as lots of sky. This will make the image more interesting. Old churches, lighthouses and other buildings can work well. You may find that you need to do one extra long exposure to get a brighter foreground that you can add in to your trails image later. Or, you may be happy with a silhouette.
As with all photography, experiment and have fun. Don’t just copy others – try to create your own style.
How long do star trails take?
This all depends on how long you want the trails to be in the final image. If you just want points of light then you need to keep the exposure under 30 seconds. If you are after long bands of light then you will need 10-30 minutes. The images on this page with the longest star trails took 30 minutes of shooting. If you want longer trails, shoot for longer! It all depends on how long you can bear to stand out in the dark and wait!
This is a short video (about 5-6 seconds) created using the images needed to make the long star trails at Happisburgh Lighthouse above. It is a time-lapse video that shows you a little of the movement of the stars (and passing planes!) over a 1/2 hour period.
© Joe Lenton, February 2015