HOW TO NOT SUCK AT STAR TRAILS

First things first, this article is essentially a companion guide to go alongside the video tutorial I did on this subject. You can find this tutorial here:

https://www.youtube.com/watch?v=VfqcWq_F6Q0

If the video was too speedy for you then this little piece will hopefully offer a bit more detail and make it slightly easier to refer back to in future.

I will preface all of this and say that I was terrified of star trails. Alright, maybe that's a little melodramatic but I did always think that they were far more complicated or imposing than they actually are. The process can be quite long-winded but it's a bit like fishing; you set everything up with all the correct settings, wait, process the images and then, after all that time, the final image is revealed. It's so rewarding and with long dark winters, it's the perfect time to give it a go!

What is a Star Trail?

A star trail is a stack of multiple images on top of each other. Over a prolonged period, we can see the earth's rotation in relation to the stars and it will create circles, lines, curves and plenty of other patterns depending on your orientation and location.

The north star, Polaris, is the star that all others appear to rotate around. So if you're after concentric circles then facing the north star is essential (if you're in the northern hemisphere).

The above image is taken from PhotoPills - an app which I cannot speak highly enough of. But you can see how different directions will give different results when it comes to star trails.

The length of a star trail depends on three factors:

1. the length of each exposure
2. the duration of the shoot
3. the number of images

We will discuss these as we go forward but adjusting each of these factors will lead to very different results.

What do I need to create a star trail?

This is pretty simple really. You will need:

1. a camera
2. a tripod
3. an intervalometer (unless your camera has an in-built one)
4. a computer or laptop
5. star stacking software
6. A dark night sky

1. A camera

Not all cameras are created equal and it’s super important that you know the constraints of your make and model. Different cameras will work better or worse in low light. If you want to know more about setting up for astrophotography then you can read this blog post.

2. A tripod

Assuming you’re not shooting in gale-force winds you don’t need a rugged, solid tripod. A cheap one will do. Essentially you need to be certain that the camera will not move for the whole shoot. Any movement will be picked up and so buying a decent tripod can help that.

3. An intervalometer

This bit of kit is fast becoming a little archaic. More and more modern cameras have an intervalometer built in which makes time-lapses and star trails much easier. An intervalometer, whether in-built or external, is essential though. By dialling in different settings one can tell the camera:

• When to start shooting
• How many images to take
• How long to wait in between each shot
• How long the shutter should be open for each shot

Here’s a link to a couple of intervalometer options. Just make sure that you get the correct one for your camera. 

4. A computer or laptop

This is a bit of a no-brainer. But you will obviously need a computer to be able to run the software required to stack an image. It doesn’t need to be particularly powerful but slower computers will sometimes crash if they don’t have enough RAM to manage hundreds of files. 

5. Star Stacking Software

There are a few options here and a simple google of stacking software will yield plenty of results but I will say that I have used Star Stax for a while now and it’s all I need. It’s incredibly simplistic and foolproof. You just dump all the images into the programme, hit run, and *poof* there’s your image. Here’s a link to that software should you wish to download it.

6. A dark night sky

alright so you can't really guarantee this but looking at lots of weather apps like Windy, BBC Weather or Met Office will help you out. It's also a good idea to pick a time when the moon is at it's smallest as the light from the moon can disrupt results.

Planning the shoot

Right. So... you’ve got all the gear. Tonight the sky looks clear and still. You want to go and do a star trail. First of all, you need to plan. You might already have a good idea of what you want to photograph but you need to ensure it will remain still throughout the shoot. Buildings, rocks, and mountains are good. Sheep, people, trees, etc are not. Pick a good subject and then work out your shot. If you want to plan where the moon, stars, and galactic centre will be then I would recommend an app called PhotoPills which offers a multitude of information including a star trail calculator and an astrophotography mapper. You can place a pin anywhere on a map and work out the best angle to photograph your subject. I use it all the time and it is really really helpful. 

I would say however that there is no better way to plan your shot than to get out on the ground and look at it in daylight. That way you can move around it and work out where to place the tripod. 

A good example of this, and a time I messed up, was when we were in Scotland and I wanted to shoot this star stack behind a huge rock promontory on the beach. I’d seen photos of it and I assumed it would be easy to photograph. I fired up PhotoPills and planned where to put the tripod - because it’s a top-down view, it looked really simple to get from the car park to the beach. However, when I arrived it became apparent that the beach in question was at the bottom of a 50ft cliff so I can reassess. My advice now is to get on the ground and check first. The below image was from this attempt, I found a nearby tower and used that instead of the rocks.

Settings on the ground

Once you have a plan of action and it’s go-time, you will need to head out and set up. You want to use a nice wide lens with a wide aperture to let lots of light in. I personally use a beautiful 14mm f1.8 lens which is perfect for lots of detail. Although to be honest, anything less than 50mm will work and anything around f2.8 or faster will be fine. Try it on an astro shoot beforehand. 

Once you’re happy with your kit and your composition (remember your orientation to Polaris) you’ll need to dial in your settings. 

1. Focus on the subject. Use manual focus not autofocus - you don’t want to camera to shift focus halfway through the shoot. If you’re struggling to find enough light to focus on your subject, I have a little hack. Put your phone torch on and put it on the subject facing your camera. Then adjust the camera’s focus until the torch light is as small and pin-sharp as possible. 
2. The Aperture needs to be wide. Ideally *just* before it’s wide open. So for example, if you’re using an f1.8, try and shoot at f2.0 or f2.2. This way you can avoid any softness in the corners through diffraction. 
3. ISO should be set manually. Anywhere from 100-1000 but I wouldn’t go much higher than that, especially if you’re shooting on a crop sensor. 
4. Shutter speed should be utilising the 500 rule. If you don’t know what that is then you should read this blog post to help. Most of the time my shutter will be around the 10-20 second mark to get lots of light onto the sensor. 

Set your intervalometer up to take one image, wait a couple of seconds and then take another image. I set mine up to wait 3 seconds between each shot and to take 1000 images.

Here’s an example of my settings and the image it created:

Focus	Aperture	Shutterspeed	ISO
Manual	f2.2	12"	500

250 images, 3 seconds between each exposure

After this, all you have to do is click the shutter and walk away. You can leave the camera doing its work for an hour or so before coming back. the longer you leave the camera, the longer the trails will be.

Post Processing

When you eventually return to your camera, you may well find that you have hundreds of images on your SD card to trawl through. It’s not too bad though because in theory, if you’ve done everything correctly, the entire set of images should be identical in their settings. So if you edit one, you can copy and paste all those changes to the others. 

I’m not going to go into much detail about the editing process - if you want to see what I did then take a look at the video at the top. But essentially I will darken the sky and boost the contrast a little bit. I will then select the foreground and bring up the shadows and brightness a little to make it stand out a little. Each image will be given a temperature and hue value. Make sure you copy and apply the same hue and temperature value to all the images. If you don’t then the images won’t look right when stacked. I’ll then apply all those edits to the set before exporting. Save the completed images to a folder without anything else in it to save time later. 

This next bit is a right faff. It’s not essential but, because the stacking software will pick up all movement of light onto the sensor, if a plane or a car or a torch has passed in front of the camera it will stand out and potentially ruin the image. In order to fix this you need to go through the entire set of images and remove any errors. You’ll recognise them quickly though because they will look like streaks of light in an otherwise uniform image. It takes time but it’s worth it. 

After you’ve done all that, you’re nearly there! 

StarStacking! 

This is the easiest bit. Open up StarStax (or similar software) and load in your images. Hit “go” and let the software get to work. You should see your image forming and eventually it will spit out the result. You can play around with a couple of small changes like the meteor mode, or the length of the trails etc. but the image should be pretty much complete! Well done, all that hard work has paid off! 

BONUS! Hyperlapse your images

It always seems a shame to me to take all those images, stack them into a star stack and then dump them into the bin. Instead, they can be brought into a video editor (like Final Cut) and stitched into a hyper lapse. These are hugely impactful because they can show huge passages of time passing in just a few seconds. 

To do this, import all the images into the timeline. Select all the images and change the duration to 0.1 seconds. In Final Cut, you can then make them into a compound clip (I’m not sure if you can do this in Premiere Pro) and then add effects like Ken Burns or a panning shot or sound effects etc. 

It’s really easy and can help tell the story of your finished star stack too. Here’s an example of some of the hyper lapses I’ve done: 

https://videopress.com/v/j8k3zGiM?resizeToParent=true&cover=true&preloadContent=metadata&useAverageColor=true

https://videopress.com/v/braYTwhn?resizeToParent=true&cover=true&preloadContent=metadata&useAverageColor=true

Conclusion

Hopefully this has opened your eyes to the wonder of star trails and shown that they really aren't as complicated or scary as they first appear. If it has been helpful please consider sharing this blog around or letting me know via my Instagram @willhall.wildlife

Thanks for reading and until next time, happy shooting!