Star Trails Tutorial
Temple of the Moon - Star TrailsA colorful Star Trails image over the Temple of the Moon
Planning
A clear sky is one of the most important things to watch for when planning a Star Trails photo. In order to get a spectacular Star Trails image, you should try to have a completely clear sky for the duration of your shoot. I would highly recommend using Clear Dark Sky charts to help you pick a good night. These charts can be a bit difficult to understand at first. Basically, the more rows of dark blue squares, the better.
The great thing about star trails is that you do not need a dark sky to get a beautiful image. Even in light polluted areas, you can still capture a great star trails photo. You can also do star trails image during a full moon.
Gear
Capturing star trails doesn't require expensive gear. All you need is a camera with an intervalometer and a wide angle lens. Any wide angle lens will do, even ones that have bad coma. Since all of your exposures will be blended, the star distortion is not an issue. Personally, I would recommend using a Full-Frame camera with a 14mm lens. This allows you to capture a large portion of the sky and a foreground. Alternatively, you can set your camera to capture 90% sky for the star trails photos. For the foreground, take 1 photo at the beginning or end of the shoot. You can merge the two exposures in Photoshop.
If your camera does not have a built in intervalometer, you will need to purchase a remote that has this capability. I use a Vello Shutterboss II for some of my astro, it works great.
Of course, you'll also need a sturdy tripod and ballhead to make sure the camera does not move over the hours. I use a Feisol CT-3441T tripod and an Acratech GP Ballhead. Both are quite expensive, but they do a great job for all kinds of photography.
SD Card Considerations
A large, fast SD card is recommended. You will be shooting potentially hundreds of Long Exposure photographs one-after-the-other for up to 6 hours straight! You cannot afford to have your SD Card get bogged down, as it will completely mess up the interval.
The SD Association has created a graph that clearly explains what all the numbers on the card actually mean. You will need a Class 10 or UHS Class 3 card to be able to successfully capture Star Trails. You can always test your camera out before leaving the house, to see if your current SD card is fast enough.
I use these 32 GB SanDisk cards in my D750. The 32 GB card holds roughly 1,000 uncompressed 14 bit RAW images at 24 megapixels. If you do not use a fast enough SD Card, your camera may need extra time to process each RAW file, potentially causing gaps in your star trails. If you have a very high-resolution camera, like the Nikon D850, you'll likely want a 128GB card to hold enough images.
Camera Settings
Before you take your Star Trails photo, you need to decide how you want the final image to look. If you shoot at a high ISO (1600+) you will have tons of stars in your image and your Star Trails will be very dense and bright. If you shoot at a lower ISO (100-800) you will have far fewer stars, more star colors, and your Star Trails will have some space between them. Click here to see the difference between ISO 100 - 6400, it should give you a good idea of how many stars you can capture. Therefore, there are no "default camera settings" when photographing Star Trails, it's entirely up to you! With that being said, here's some settings to get you started:
- Manual Mode
- Manual Focus (Camera Body and Lens)
- f/2.8 or f/4
- ISO 800
- 20 -30 second Shutter Speed
- 3000 - 5200 K White Balance (Don't leave on Auto)
- Long Exposure Noise Reduction - OFF
Many people recommend using ISO 1600+ when shooting at night. However, this has the potential to clip the highlights (stars). Since our entire image is focused on the stars, this isn't good! You might be surprised at the star colors you can capture when you use a lower ISO. Therefore, if you want to try something a bit different, use a lower ISO for one of your star trails sessions! I recommend between ISO 400 - 800.
If you use a substantially lower ISO, you could also take longer exposures. Instead of taking 20 - 30 second images, you could take 1 or even 2 minute exposures! These longer exposures would capture more light, resulting in a cleaner image, with less grain. It doesn't matter that the stars will show motion in each photo, we are creating a star trails image after all.
The great thing with a star trails photo is that you have so much flexibility! You can try a lot of different techniques and still get a great final image. There is one thing to watch out for though - your interval. If your interval is not set properly you will have major problems!
Determine Your Interval
The trickiest part of doing a Star Trails photoshoot is setting up the Intervalometer properly. I'm going to simplify this as much as possible right now, then go into a lot more detail later. Your Interval is either 1 second, or 1 second longer than your shutter speed. This is all you really need to know. If you get confused later on, just remember these two options and try them both on your camera. Since cameras are programmed differently, you need to decide which option works for your particular model.
I shoot with a Nikon D750, so I have this interval function built into the camera menu. Look for the "Interval Timer Shooting" in the "Photo Shooting Menu." Nikon should have guides on their website for different camera models. Keep in mind, many of the cheaper camera models, like the D3300, do not have a built in Intervalometer. You will need to purchase an external remote that plugs into the camera. I recently purchased this Vello intervalometer for doing tracked astrophotography.
Lonely Speck has compiled a list of cameras that have built-in intervalometers, head over to their website to see if your camera has this function.
Using a Nikon D750, my built-in intervalometer has a couple different parameters:
- Start Options
- Interval
- Number of Intervals
- Exposure Smoothing
The Interval we choose is entirely dependent on the Shutter Speed. You can set the interval to any combination of hours / minutes / seconds. For this example, I am using my Rokinon 14mm with a 20 Second Shutter Speed. If I set the Shutter Speed to 20 seconds and the Interval to 20 seconds I will have problems. The camera needs time to save each exposure to your SD card and close the shutter. Therefore, the Interval needs to be longer than the Shutter Speed. I have found that setting the Interval 1 second longer than the shutter speed is usually fine on my Nikon camera and Vello remote.
Some camera brands are programmed differently, and they require a 1 Second interval. Therefore, if your shutter Speed was 20 seconds, your interval would simply be 1 second. If you tried using a 21 second interval, you would have a large gap between each photo. Before you head out of the night, determine which way your camera works! Your interval will either be 1 second longer than your shutter speed, or just 1 second. Try both options and see what happens. You should hear the camera go "click..click" That indicates that the exposure ended and another one began. If you only hear "click", and then a long pause, your interval is not set properly.
I've noticed something strange when using a 30 second shutter speed. When I would set the Interval to 31 seconds, the camera would keep skipping a frame. Confused, I pulled out my smartphone timer and timed the 30 second exposure. It turns out, a 30 second exposure is actually 32 seconds long! After some more testing, I also realized that a 15 second photo is actually 16 seconds long! I imagine this is done to follow the doubling principle of Stops. For example, 1 second / 2 seconds / 4 seconds / 8 seconds / 16 seconds / 32 seconds. This would explain why the camera is not taking the actual length specified. Therefore, if you are setting your Interval to 1 second longer than the shutter speed, be sure to account for this. A 30 second shutter speed needs a 33 second interval, and a 15 second shutter speed needs a 17 second interval. Of course, you could also try a simple 1 second interval and see if that works.
Sit with your camera and listen, you will be able to hear if things are working properly. The camera shutter should open, take in light for 20 seconds (or whatever your shutter speed is), then close the shutter. Almost immediately after the shutter closes it should open again and repeat the process. If there is a long delay between photos, your Interval is not right. If you hear a long gap, try using an Interval of just 1 second. You should now hear "Click..Click", indicating the exposure ended and a new one began.
You also need to determine the Number of Intervals, or photos, you want. If you have all night and a fully charged battery, you can set this for a couple hundred exposures. 300 photos (with a shutter speed of 30 seconds and Interval of 33 seconds) will take about 2.5 hours. The amount of exposures will also change the look of the Star Trails. The more exposures you take, the longer the star trails will look. I normally set my camera to take 100 - 200 Intervals. However, if I am camping next to my camera, I will set the number of exposures to 500 or 600. Once I verify the interval is working correctly, I can go to bed and let my camera get to work! In the morning, I go over and turn off the camera and pack everything up.
Star Trails over Mosquito Lake, Ohio
Choosing your Style
Star Trails give you a lot of freedom to create a unique image. Depending on your Shutter Speed and ISO you can create a lot of different effects. For example, if you shoot at a lower ISO (400-800) or a shorter shutter speed (10-20 seconds) you will pick up less stars. If the Full Moon is out, you may need to adjust your settings to account for the extreme amount of light, compared to a dark moonless night. The image below was taken during a Full Moon, which exposed the foreground nicely.
Star Trails under a Full Moon
Finally, the direction you face will completely change the look of the photo. Facing North gives you the cool circular effect, while facing South produces a wall of Stars. Depending on your Latitude, the North Star (and resulting circle) will be higher or lower in the sky.
North:
Star Trails over the Great Sand Dunes, Colorado.
South:
Star Trails facing South
East:
Star Trails facing East
West:
Star Trails facing West
Telephoto Trails
If you don't want to spend all night for one star trails image, there's a much faster way - use a telephoto lens! As you zoom in on the stars, their apparent movement speeds up. The photo below was only 4 minutes! Use this trick to capture unique compositions with your next star trails photo.
Tips
- Set your Interval 1 second, or 1 second longer than your Shutter Speed
- Set Camera AND Lens to Manual Focus before starting the Interval
- Bring 2 fully charged batteries, verify they are charged before you leave!
- Format SD card before shooting, need a full SD card
- Make sure Long Exposure Noise Reduction and High ISO Noise Reduction are turned off
- Shoot in RAW (for more control in Post Processing)
- Don't use Auto White Balance!
- Remember, a 30 second photo is usually 32 seconds!
- A 15 second photo is actually 16 seconds!
Facing South-West in Boulder
Post Production
StarStaX
StarStaX is a free program that allows you to easily create a Star Trails photo. This application will take all of your photos and blend them together. You can choose from a variety of methods including Gap-Filling and Comet Trails. StarStaX will also allow you to use a Dark Frame, if you remembered to take one after shooting all of exposures. This Dark Frame will help to eliminate hot pixels.
StarStaX also has one of my favorite functions, Cumulative Blend. If you toggle this mode, StarStaX will process each photo and save the composite image. This will allow you to create a Star Trails video. See the video below for an example.
I recently created a YouTube tutorial that explains how to create a timelapse like the video above. You will need StarStaX and Photoshop for this workflow. You can watch the tutorial below:
Photoshop
I find that Photoshop creates the highest quality Star Trails. However, this is by far the hardest and most time-consuming option. I would recommend most people stick with StarStaX. You will need a powerful computer (SSD, 16 GBs of RAM) to handle this method, as you will be layering dozens of photos together. Watch my Star Trail tutorial for a complete guide to post-processing your images.
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