Creating star trails - step by step

 Star Trail Photography 

I was a day late for the peak of this year's Perseids meteor shower. Nevertheless I decided to go outside at 11pm to see if I could see any meteors and even be lucky enough to capture some on camera.

Being ready with camera in hand just won't work for this sort of photography. For one thing, hand held will NOT allow slow enough shutter speeds to be used successfully. Another thing is that no sooner have your reactions noticed a meteor than it has gone - they travel exceedingly quickly across the sky. You have no chance of spotting it and focusing on it to take a picture in time.

Star trails over an old oak tree

In order to give myself a chance of capturing some meteors I set up my main camera on a tripod, pointed it towards the northern sky (that is where the Perseid meteors will be originating). I messed about with manual focus until I was happy that I was getting sharp enough stars being recorded, then I set up my camera to do Interval Timer Shooting (or time lapse captures). This involves setting a start time, how frequently you want the camera to take an image  and the number of frames you want it to record.

I also had a second camera outside with me which I set up using a small tripod on a garden table and pointed this one towards the Milky Way in the southern sky.

Now, as I watched and waited, over the next two hours I did manage to spot about six meteors. Some of these were in the northern sky so should have been caught on my main camera. However, my luck wasn't holding and not a single frame managed to include a meteor!

I was a little luckier with the other camera, although this has a smaller sensor it still allows a time lapse to be set up, and even creates videos of the resulting images. On careful inspection I did spot a couple of meteors on these shots, plus a few planes too...

Small meteor can be seen top right

After the initial disappointment of not capturing any meteors on the main camera I realised that I had all of the images taken from exactly the same location and the pole star was fairly central to the composition so I merged all the images together into a single image producing the star trail photo above.

There were a number of frames that had thin cloud moving across so I left them out of the final merged image, which is why there are some gaps in the flow of the stars. It really makes you think about how the earth rotates when you see this amount of movement over a couple of hours!

If I had intended on making a star trail from the start I would have used a much longer shutter speed, but because I was hoping to get sharp images of individual stars and meteors I kept my speed down to below 15 seconds so the rotation of the earth doesn't blur the stars.

Here is my quick and easy way to create your own star trail photograph with the settings I used:

Camera - it is best if the camera has a time lapse function, otherwise you will need an extra piece of kit called an intervalometer, or a remote release cable and be ready to press it over and over again...

Lens - use a wide angle lens with your fastest aperture (ie lowest number aperture) eg f/1.4 or f/2.8 if possible. You need to capture as much light as possible and the widest aperture will allow this.

Focus - set your focus to manual not automatic, then manually focus on a bright star. This is not all that easy to do so take as many test shots as you need until you are happy that the star is sharply in focus.

Tripod - or some way to hold your camera completely still. If your camera has Image Stabilisation turn this OFF if you are using a tripod.

Point the camera in the direction of the Pole Star (Polaris) this points to north so if you have a compass that is the direction to look in. If you can't find the Pole Star use a free app called SkyView Lite on your mobile phone and search for Polaris or Pole Star - it will point an arrow in the direction to move the phone until you see where Polaris is located.

Now for camera settings.  

Use RAW image capture if you can. If not, use best quality JPEG.

Aperture, as mentioned, should be the widest (fastest) your camera lens can set. 

Shutter speed - if you want sharp, not moving, stars keep the speed to between 10 - 15 seconds. If your intention is to capture the movement in one frame or just a few then slow down the speed to 30 seconds or more.

ISO - I would recommend a minimum of ISO 1600 if your camera can do this. If you are using longer shutter speeds the ISO can be lower, eg 800. ISO above 1600 will probably result in 'noisy' images, depending on your camera.

Take a test shot to see if the result is OK before you set off the time lapse or intervalometer. 

Set your interval timer or time lapse. I set mine to take a photo every 25 seconds and to do this 30 times. I set this off a few times and ended up with over 120 images. Each shot was set to a shutter speed of 15 seconds.

Use a camera release (cable or wireless) to take the first shot that starts the sequence. If you can't do this use the self timer set to 2 seconds if the camera has this function. If neither of these things are available just press the shutter button very carefully so you don't move the camera.

Now you just need to wait while your camera does all the work!

Post Processing

If you captured your images in RAW format you will need to do some post processing on these. I use Adobe Lightroom for this. Check the first image for white balance, increasing the contrast and clarity a bit might improve the image too. When you are happy with your edit on the first image copy the settings to the rest of the photos. That way they will merge together better.  Save your edited images.

If you captured JPEGs you can still do some extra contrast and clarity, just not as much as with a RAW image.

Now for the fun part. Use a free program called StarStaX  and load up your images (drag and drop) into this. tick the ones you want to include in the merges star trail image. I removed the ticks from any of mine that had clouds obscuring the sky. Set the blending mode to Gap Filling and then press Process. The merged image will build up on the screen and you can save it when it completes the process.

I'd love to see what you create so drop a comment below with the star trail, or leave a link to the image so I can take a look.

Have fun.