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A Complete Guide to Star Trailing

Ever see those pictures where the stars streak across the sky in a big arc? Or maybe the whole sky looked like it was spinning? What you saw was star trails. The streaks were light left behind on the sensor or film from the star as it traveled across the sky in front of an open camera shutter. In fact, what are being recorded are stationary stars and the rotation of the earth as it spins past them. For me, the images seem to have a certain magic or mystery about them.

You must have heard a photographer talking about capturing that perfect moment in time. Well for capturing star trails you will need to capture the perfect hour or two in time. For such amazing looking images, the technique used to capture them is really quite simple. Keep reading for a complete set of instructions from start to finish.

150 minutes of night sky captured over Salt Spring Island, BC, Canada.

What Do I Need?

Before you gas up the car and head out in to the night check the list below to make sure you have all the required gear.

  • A camera capable of shooting in “Bulb” mode
  • A sturdy tripod
  • A cable or shutter release *it can be done with a remote but options will be very limited

Some things that you will find useful (but are not necessary to get started) might be: a decent flashlight, some extra warm clothing and anything else to prepare you for the weather and elements. If you are heading into a remote location it may be much colder than what you are used to at night where you live, so be prepared.

Where Should I Go?

I tend to look for locations that are have some foreground interest. It may be an abandoned building, large infrastructure like a radio tower or a bridge, or some natural features like rock formations or big trees.

You may choose to add light to these features with a flashlight or keep them as silhouettes against the star-filled sky. Though it is possible to capture star trails in town, it is much easier if you try this far away from any city lights. A darker sky means a greater number of visible stars.

It really pays off to do some research before embarking on a shoot, especially if you have never seen the location in the day before. You should also check the moon schedule before heading out. You will want to know how bright the moon is, the moon rise and set times as well its location in the sky (there are many smartphone and iPad apps for this).

A moon can work to your advantage lighting up the foreground for you but it can also reduce the number of visible stars, or just be in the way of what you are trying to shoot.

How Do I Get Started?

There are multiple ways to go about shooting star trails. I will start with the basics that do not change whether you are using an analog SLR or a DSLR.

Before dialing in any settings you should go ahead and mount your camera onto a tripod. Roughly compose your shot and set the focus. In the dark, it is not easy to get the AF to lock on to anything but do not worry, as there are several solutions to this.

If you are including foreground objects, I suggest making sure that they are in focus. If you are using a wide angle lens, the foreground object and the stars will probably both be in focus even at a very wide aperture.

I find that it is fairly safe to just set the focus to infinity if it is a wide angle or fisheye lens, right from the start.

Some lenses will not have those markings, so shining the light on the foreground subject while using the AF function may work if the flashlight is bright.

If not, go lay the flashlight on the ground at the base of what you are shooting and focus on that. Once you have achieved the glorious state of “in focus”, be sure to set it to MF or manual focus before starting your exposure or it will start searching again when you start the exposure and you will lose your focus and have to repeat the whole process again.

So now you should have your camera focused and set to manual focus (MF) and the shot roughly composed. When composing the shot try not to include any direct light sources (e.g. streetlights) in the shot.

If you are not using film then I suggest doing a test shot which aids in composing your final shot. A 2-3 minute exposure at high ISO and wide aperture is enough to be able to see which direction the stars are moving and allow one to imagine what the final shot will look like.

Recompose the shot if necessary and zoom in on the LCD to double check you focus is accurate. Be sure not to bump the focus ring while recomposing!

But What About White Balance?

White balance could be a whole separate tutorial on its own, so I will keep this really brief. If you would like to know more about white balance, check out this article on Cambridge in Color.

White balance is the relative warmth or coolness of white light. A white object appears slightly blue with a cold color temperature and it looks slightly orange with a warm color temperature. I tend to shoot night skies with the white balance set to “tungsten,” which gives a nice blue look to the sky or the extreme opposite of 10000 Kelvin giving it a deep orange color.

The photo above has a white balance of 10,000 Kelvin and the photo below has a white balance of Tungsten.

I find that Auto white balance leaves the sky brownish or “dirty” looking. You will have to refer to your camera’s manual if you do not know how to change these settings. These setting will affect the whole image, so if you are going to include some foreground objects, you’ll will need to consider what you are using to light them with.

I use a variety of flashlights for this job and my white balance settings help me to determine which one to use.

LED light is very blue, so if you are shooting with your white balance set to tungsten, the objects lit with it may look unnaturally blue. To avoid this I use a xenon flashlight or flashlight with an incandescent bulb which have a much higher or warmer color temperature which neutralizes the blue effect of the white balance leaving objects a natural or true color.

If LED is your only choice then consider putting some orange cellophane over the front to alter the shade of the light but doing this will reduce it effective power.

If I am shooting with my white balance set to 10000 Kelvin then I would generally use an LED which is the exact opposite of the above situation. Its bluish hue would neutralize the high color temperature of 10000K leaving the objects lit with it a natural or true color.

So for a cool white balance use a warm light and for a warm white balance use a cool light for lighting your foreground interest and other things within the frame.

In the image on the below, the white balance was set to tungsten giving the sky a deep blue color and the temple was lit with a warm light source neutralizing the effect of the white balance which left it a fairly natural color.

Hurry Up and Get To The Good Stuff

For shooting options, one could choose to do it all in one shot or shoot multiple shots and “stack” them after using computer software. The two photos here demonstrate the difference:

The top is a single exposure and the bottom is the exact same scene but shot in multiple frames and stacked with software. I personally find that shooting multiple images and stacking them yields much nicer images than those done all in one shot.

If you are going to do it all in one shot, then your biggest concern should be noise. You may be also limited to this method if you do not have a cable release and are using a remote. To avoid noise, one could use a narrower aperture and a lower ISO speed but these settings will typically not pick up very many stars.

If this is the route you are going to take, and I suggest at least trying it, then focus and compose the shot. Set the time value to “bulb”, the aperture to its widest, and with and ISO at 200, try for a 30-minute exposure with an aperture of 4 or 5.6. If there is too much noise then drop the ISO to 100 and either shorten the exposure time or try a narrower aperture.

If shooting this way is your only option, there is something that you can do to increase the appearance of the length of the trails in the frame that will be limited due to the short exposure time. The actual length of the trails is determined solely by time but the appearance of the trail length is determined by the focal length you are shooting at.

For example, stars over a 30-minute exposure would appear much longer in the frame at 50mm than they would at 15mm. If you find that you are limited to shorter exposure time due to noise, or any other factor, try shooting at a longer focal length to increase the appearance of the star trail length in relation to the frame. There is more on this later in this article.

My heavily preferred way of shooting is shooting multiple shots and stacking them later using computer software. Shooting this way means one can shoot with a wide aperture and a faster ISO that will pick up many more stars than the previous method. One can do this because noise becomes much less of a factor.

Noise generally increases with time so you only have to worry about 30 seconds that means even at ISO 800 it is not really going to cause a problem. There is even an option to include dark frames when stacking with software, which are frames that are completely black and can be made by simply taking a shot with the lens cap on, so that even the tiny bit of noise from ISO 800 over 30 seconds will be removed. With the higher end DSLRs and the improvement of sensor noise reduction in newer DSLRs, ISO can be bumped even higher which will result in even more visible stars streaking across the sky.

For this method it is necessary to use a cable release. You will be shooting possibly hundreds of images so it is important to make sure there is plenty of space on your memory card.

To get started, set your focus and compose your shot. Set the aperture to its widest and the ISO to 800 for starters. Dial in 30 seconds for the time value and the drive mode to “continuous shooting” mode which allows for non-stop shooting when the cable release is locked.

I suggest doing a test shot first to see if everything looks all right before locking that release. If anything is too bright then dial the ISO down or reduce the aperture. Again, the key is balance and you are balancing the ISO and aperture to get the right exposure for 30 second frames.

Too many stars over a long exposure can just be too much like this image above, which was the result of a combination of an aperture that was too wide and an ISO setting that was too high. Once you have taken the shots you will need to stack them using software.

Make sure to snap a few dark frames. Dark frames are just empty black frames that can be made by shooting with your lens cap on. You do not need to shoot with the same settings as the star images and I recommend lowering the ISO to the lowest possible setting and using a faster shutter speed. The idea behind including dark frames in a stack is to reduce noise so low ISO will help with that.

What Lenses and Focal Lengths Should I Use?

Any lens can be used for shooting star trails but you may find you will have slightly nicer results with faster lenses as this means you can keep your ISO setting low. As I mentioned earlier in the article, time determines a star trail length while the focal length determines the appearance. The image below was shot with a 15mm fisheye and is a total of 40 minutes of night sky:

Most commonly you will see star trail images shot with wide angle lenses. Most people just associate these type of shots with wider lenses just like those who shoot daytime landscapes. Not everyone has a fisheye or even a wide angle lens but that does not mean that you cannot shoot star trail images.

Now compare the fisheye image to the image here:

It is the exact same tower but shot at 85mm and for only 4 minutes. A longer focal length makes the star trails appear longer. Even though this is only 4 minutes long there is some length to the trails. Now imagine if the shot with the fisheye if it was only 4 minutes long. The trails would appear only 1/10th of the length they are now and would barely appear as trails at all.

So again, a wide angle lens is not necessary even though it is most commonly used. Another thing about longer focal lengths is they could also be more productive. If it takes less time to shoot a stack then you could get more images per outing. I also found that trying longer focal lengths had brought a renewed interest to familiar locations that I had become bored with shooting at a wide angle.

If you have a tilt shift lens try giving star trails a try with it. You can get some really interesting results that are difficult to replicate with software. The shot below was taken with a 17mm tilt shift lens.

Lighting a Foreground Interest

I mentioned above about adding light to the foreground objects and explained a few things to consider about white balance in relation to that. I often include foreground objects to complete the shots because images of just stars sometimes seem to lack a subject.

I look for interesting buildings, infrastructure or natural objects like big trees or rock formations and make them the subject of the images. I light these foreground subjects with a flashlight or speedlite. A flashlight can reach far places and can be moved around while lighting to remove shadows, like in the image below, while a speedlite can freeze a tree that may be moving in the wind.

You will probably use a flashlight most of the time because they are a much more flexible tool and leave the foreground with a much more organic look. I highly recommend doing a few lighting test shots to see how much light is needed before locking that cable release for a long set of images for a stack. Too much light will distract from that beautiful star filled sky you are about to create.

Remember that for foreground lighting use a warm color if you are using a “tungsten” white balance and use a cold color light, like LED, if you are shooting at a high color temperature. If you are stacking then I suggest doing the foreground lighting at the beginning and again at the end. I do it twice in case I screw one of them up then I have the other as a back up.

If the lighting was done in the middle shooting and a mistake was made it would leave those frames unusable. Unusable frames would create a break in the trail that would take away from the shot.

One more thing to keep in mind is your camera settings may be set to quite sensitive settings so adjust your lighting techniques to accommodate for that with low power flashes or less lighting time with a flashlight. Another handy light source for illuminating the foreground is the moon. While it does reduce the amount of visible stars it has a unique quality about it. The shot on below is a combination of moon light and orange gelled LED flashlight. The pagoda was lit with the flashlight to highlight it while the rest of the foreground was moon lit.

How to Stack the Photos

So now you have a memory card filled with image sequences and you are going to use software to stack them up to create your final star trail picture. There are several free options for this each has easy instructions on their respective homepages that guide you on how to use each one. With that said, StarStaX has recently become the software to use. It has many great options like saving frames for time lapses, gap filling and various blending modes. It is fast easy to use and everything you need it to be. It is also available across all platforms including Linux.

StarStaX: This is my favorite software. Unlike other free programs, it runs on Mac and Linux as well as Windows. What I like about StarStaX is the incredible speed. It is waaaay faster than using Photoshop and much easier as it does not require you to create any blank documents to get started. Open up the program and import your images. Hit start and within seconds your image is finished. Check out the homepage to see the great features it has.

Photoshop Stacking action: This method gets the job done but is slow and ties up memory while stacking.

Startrail.exe: One major downfall of this software is that is only available for Windows. I used this a long time ago before I started using Mac. This got the job done and before StarStaX was the standard. It got mentioned in this article out of respect for the forefathers of this technique!

Once you have your stacked image save it and drop it into your favorite editing program to continue editing if you wish. I often import the images into Lightroom and edit them before stacking. You only need to edit one and use the sync function to do the rest. Which method you choose is up to you.

By the way, this same technique works great for shooting fireflies!

About the author: Trevor Williams is a photographer based in Okayama, Japan. You can connect with him through his website, Twitter, and Facebook. This post originally appeared here.

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