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Learning how to photograph star trails is a fulfilling experience. Capturing the apparent movement of stars across the sky as the Earth rotates can give you surreal and compelling images, and star trail photography is highly rewarding if you have a bit of patience.
Interestingly, the Milky Way Galaxy is home to billions of stars out of which we are able to see only a fraction in the night sky from where we live (around 2,500 to 5,000 stars at any given time).
Indeed, if you do have the patience, (particularly if you are going to take a 2-hour long single exposure) you can turn an otherwise mundane shot into an otherworldly image.
Here is the ultimate guide explaining how to photograph star trails.
First Up – Understand The Location You Need For Star Trail Photography And Keep An Eye On The Weather
When thinking about how to photograph star trails, your goal is to allow your camera to pick up light it wouldn’t normally (ie the stars) by using extra long exposures.
So to achieve this you will need to first look for a location that is free from light pollution and a long way from the city lights.
Whether from a nearby city or the street lamp at the end of your driveway, light pollution can greatly affect long exposures. This isn't necessarily a bad thing though – in fact, it may add to the ambiance of your photo, such as a star trail image that begins during the blue hours.
Experimenting with atmospheric light can be a creative way to make a unique star trail image – just be aware that the lighter your sky is, the less contrast your star trails will have.
You will also need to make sure the moon isn't shining brightly. However, if you are looking for little ambient light to illuminate the landscape, a quarter moon is fine – but make sure it is out of the frame that you are composing.
Keep an eye on the weather and make sure that you go out to shoot on a day when the skies are clear. Obviously, you don't want to photograph star trails under a cloudy sky, but other atmospheric filters can interfere with your night photography – air pollution and humidity being the top annoyances.
The very best locations for a clear sky would be high up and away from any congested cities, and take on a night with very low humidity.
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The Gear You'll Require To Capture Dazzling Star Trails
- You will need a camera that can shoot manual mode and if it has an inbuilt intervalometer, you can make use of it to take photos continuously.
- A wide angle lens (14mm to 24mm, the wider the better) with a wide aperture of at least f2.8 for better images (but kit lenses are good for a start)
- A sturdy tripod that can hold the camera-lens combination and withstand windy conditions. Even slight movements can ruin your images
- Spare memory cards, batteries to get you through the whole shoot (a few hours)
- Protection for your gear under very cold conditions to prevent lens fogging up
- Keep yourself warm as well and have warm drinks to get you through the shoot
NOTE: It’s very important to utilize proper long exposure techniques and avoid camera shake: locking your mirror, mounting your camera on a secure tripod, and using a remote cable release for your shutter.
A Common Aperture Misconception Explained: Wide Open or Narrow?
A common question – or rather a misconception – with star trail photography is why wouldn’t you use a small aperture (say f/8 or above) for a sharper image rather than shoot wide open? You’re already shooting hour-long exposures so the timing isn’t a concern….surely it’s better to have a sharper photo, especially if you have other focal points (foreground interest, etc).
The issue with photographing stars is that they move – this is why we want to photograph their trails in the first place. With that in mind, there is a delicate balance to find with your exposure that’s more than just how long your shutter is open.
Wider apertures allow for shorter exposure times because they let more light in than narrow apertures. Focus on that last part – they let more light in.
Considering that stars are constantly moving, you need to make sure that they’re registered on your sensor before they move – otherwise, your star trails will be very dim, perhaps even non-existent depending on your chosen f/stop. Imagine doing a two-hour shoot where your foreground is lit nicely, but your star trails look no more than a slight variation in tones on the night sky.
So it's a good idea to have a lens that’s capable of very wide apertures – such as f/2.8 or even wider. The wider your aperture, the brighter your star trails will be.
How To Photograph Star Trails By 2 Different Methods
So you've chosen a location and you have the gear, so the next step…how do you get those fantastic lines of light?
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Photo by Robert Hensley
There are two methods popular with star photographers:
- Using one very long exposure (long enough to register some noticeable star movement; at least 30 minutes) OR
- Taking many shorter exposures and stacking those images in a way that shows sequential movement.
Here are the two methods explained
1. Using One Very Long Exposure To Capture Star Trails
To capture star trails using one long exposure, there are a couple of important things to consider. You need to let as much light into your lens as possible for those stars to register (the why's of this are explained below) – this means using a fast lens, preferably in the f/2.8 range.
When photographing stars under one exposure, you need to do it during a new moon night – meaning that the moon is nowhere to be seen. If you have anything more than a crescent, your exposure will be limited to the 10-minute range because of the ambient light, which won’t do much for star trails. For this kind of photography, darkness is your best friend.
Ultimately, you’re aiming for your environment to be illuminated by the stars themselves – yes it’s possible! However, this entirely depends on the length of your exposure. The image below is the result of an 80-minute exposure taken under a new moon – you can see that the foreground is exposed nicely and the star trails are outstanding.
When calculating your exposure, it would be best to do a shortened test shot so you’re not waiting a ridiculous amount of time just to see if your settings are correct. Many night photographers will jack up their ISO as far as it’ll go and shoot wide open – you’ll rarely find an instance where you’ll be taking a photo shorter than 30 seconds here. Of course, the test shot will be entirely unusable due to noise and lack of trails, but it will give you a base to calculate what settings are needed with an ISO of 100.
Here it is step-by-step
- Make sure that the moon is nowhere in the sky
- Base your exposure time on your test shots. If you have an f2.8 lens, shoot at ISO 100 and if you are using a narrow aperture like f4 or f5.6, use ISO 200 or 320
- Keep your ISO really low to reduce noise. Start with a moderate aperture of f4 and make changes later.
- Do a test shot first for 20 or 30 seconds to see if stars get recorded in the frame. If the test shot does not go well, widen the aperture or increase the ISO, whichever is possible or do both and take test shots till you get a good image.
- Once you are happy with your test shot, increase the shutter speed to around 10 or 15 minutes. Take the shot and see how much trails you get and how bright the trails are. Do a few test shots by doubling the exposure time to get the settings right.
- Do not turn on noise reduction as that process can consume a huge amount of time after each exposure.
- Now depending on what you observe from the test shots, calculate how much exposure you will need to get decent star trails in your image. You will definitely need a minimum of 60 minutes exposure, but a 90 minutes exposure can get you some brilliant trails in your images.
- Bear in mind, total darkness is your friend for this very long exposure photography and make sure you have your battery fully charged to last through the entire exposure.
2. Image Stacking Shorter Exposures
An alternative to waiting for an hour or more for your exposure to finish is to take sequential images and stack them together in post process to get your star trails.
In short, your exposure should be just long enough to register your stars as bright objects in the sky before moving onto the next one. It’s not uncommon to have several hundred images to stack taken over the course of a few hours.
Here it is step-by-step:
- Have your aperture set to the widest, ISO around 320 to 640 and shutter speed 20 seconds. Manually focus on a bright star in the sky (do this by zooming in on live view). Take a test shot and review your image.
- Make sure you turn off in-camera noise reductions like long exposure noise reduction, high iso noise reduction, low light noise reduction (anything that is in the shooting menu of your camera) as this can cause a huge delay in time between long exposure shots
- Make a test shot and depending on how the stars get recorded in the image, you may need to increase ISO and/or shutter speed. Do not increase the ISO above 3200 as the image quality will start to degrade.