How to Photograph Star Trails: The Ultimate Guide

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Avatar of Christopher O'Donnell
I'm a professional landscape photographer living on the coast of Maine. Through my work, I like to show a vantage point that is rarely seen in reality; a show of beauty, emotion, and serenity. Feel free to visit my website.

Photographing the night sky can be a surreal experience, and star trail photography is highly rewarding if you have a bit of patience. Those 2 hour long single exposures can turn an otherwise mundane day shot into an otherworldly image.

Racing Stars
Photo by Andrew Stawarz

When photographing star trails, your goal is to allow your camera to pick up light it wouldn’t normally by using extra long exposures. Working under the night sky means that the amount of available light is severely limited – most likely, you’ll only be able to capture the stars in the sky depending on if there are other light sources around, unless you’re planning on spending a few hours for each exposure.

With that being said, it’s very important to utilize proper long exposure techniques: locking your mirror, mounting your camera on a secure tripod, and using a remote cable release for your shutter.

However, there are additional things to consider when photographing star trails that will set your night images apart from the crowd – how do you get those fantastic lines of light?

Star Trails
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.

One Long Exposure

To capture star trails using one long exposure, there are a couple 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.

The vortex in the sky
Photo by .Bala

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.

Image Stacking Shorter Exposures

An alternative to waiting 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.

Post process software such as ImageStacker and DeepSkyStacker will automatically throw all your images together and produce a stunning star trail.

Another benefit to image stacking is that you have all the necessary photos to make a time lapse video – here’s a short clip of what you can accomplish with this method of star trail photography: both the time lapse video and the composite trail image are shown here.

Tip: Between shots, try waiting a few seconds to let your sensor cool down a bit as a hot sensor = more digital noise.

Aperture: Wide Open or Narrow?

A common question – or rather 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.

Considering this, 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.

Finding the Poles

As you may have noticed, several of the example images used here have a circular pattern around a more central location- also known as the north and south poles. This is especially apparent in the video link above. In order to replicate this, you need to locate the poles first and aim your camera for it.

If you’re an astronomy beginner like me, this may seem a bit daunting – not to worry though. If you’re shooting towards the north pole, the Polaris (a.k.a. the North Star) is what you’re aiming for – it’s the last star on the handle of the Big Dipper, so if you locate that you’re good to go.

The south pole is a bit more difficult to eyeball as there’s no prominent bright star near the pole to help like the Polaris. You can still gather an idea of where it is though by using this free software to help pinpoint the south and north poles – very handy.

More Tips

Light Pollution – 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.

Clear Skies and Dry Air – 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 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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37 thoughts on “How to Photograph Star Trails: The Ultimate Guide

  1. Matt

    Some good stuff here, but my main question still remains: How do you successfully get the foreground in focus as well as the stars when using wide apertures? Does it all come down to knowing hyperfocal distance?

    1. Avatar of Christopher O'DonnellChristopher O'Donnell Post author

      Pretty much Matt – there’s not much you can do to get your foreground in tack-sharp focus when you’re shooting at f/2.8 and aiming towards the sky. A good amount of distance between your camera and foreground will help. You can also trying experimenting with focusing on your foreground and seeing how your stars appear…..this will all depend on your focal length, distances between subjects, etc…but as long as you’re happy with the results that’s all that matters.

      There is also the option of blending two exposures together….one focused on the sky and another focused on your foreground….might be tricky blending but I’ve seen great results using this method. Bring along a flashlight to help you focus on the foreground.

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  3. Avatar of Francois StequeFrancois Steque

    Very good article, I read many but this is one of the best. The aperture consideration is a really good tip, I shot a star trail last saturday and wished I had read this before, it explains why the star trails are not as bright as I thought, I am not a big fan of the 30 second and stacking method due to the amount of post editing and processing but it has merits, there nothing more annoying than having a jumbo jet cross the sky duting an hour long exposure.
    I use an Iphone app called starwalk to spot Polaris in the sky, and point my camera around there. another good tip you don’t always have to shoot at a new moon there are plenty of nights when the moon sets quite early and it is dark enough afterwards.

  4. Avatar of Christopher O'DonnellChristopher O'Donnell Post author

    Another great tip from Mike on the Light Stalking facebook page:

    “Another tip: Turn off VR/IS (Vibration Reduction/Image Stabilization) on your lenses. The lens will try to counter normal earth movement and can actually add blur to the images.”

  5. jvictor

    80 min long single exposure ? What about the sensor heating up and messing up the image – “amp glow” , maybe sensor chilling must be mentioned here.

  6. christa farrar

    i am just starting out as well . ok so the lowest f stop( mine is 4 ) . i want to include the foreground and ill start by going a distance away. im using 70mm but my camera has a tough time focusing – should i try manual focus? i really want to do this again but want to get foreground. thanks for the help

  7. Shutterbug

    Great article but i have come across a lot of people talking about sensor heating and reducing the sensor life and also the battery drain…Any takes chris?

  8. Van

    Polaris is the last star of Ursa Minor, the Little Bear (Little Dipper). You can locate it using the Big Bear (BD). Beautifuls shots! Thanks for the info!!!

  9. Xtine

    Thanks for the informative article! I cannot wait to try this! Come on sun, set already! I have a Tokina 11-16mm f/2.8 which I think will be perfect for this project. I just captured 30 seconds of the International Space Station passing overhead and did notice the short star trails around it. Fascinating! Thanks again!

  10. sam

    hi chris,

    i am interested in shooting star trails but my only wide angle lens is a 12-24 f4… i am currently using a nikon dx body.

    is the maximum aperture of f4 sufficient if i were to use the 30-second stacking method? or should i procure another wide-angle? the only 2.8 lens i have is a 70-200, hardly a suitable focal length.

    Would appreciate your help :)

  11. Joe

    As far as using the one long exposure method, when you take the test using a high iso, how do you do the calculations to find your new exposure using an iso of 100?

  12. Steve

    Nived,
    Put the setting on bulb and use a remote cable shouter release, lock it open and youmcan have a shutter speed as long as you wish.
    Ps I have a 550d

  13. Stephen

    Great article. Concise and to the point.

    You mention “Considering that stars are constantly moving, don’t you mean that the earth is constantly moving?

    The visible motion of the stars is due to the motion of the Earth; the stars remain in the same position relative to each other, but seem to move across our sky because the Earth itself is moving around the Sun.

    1. Francisco

      it’s happened to me lots of times and found out that if you set the focus on auto and if you’re doing it with a remote shutter/timer, you are not giving enough delay time for the camera to focus and start shooting.

      to avoid it, i set the focus manually (not the best in my case, still rookie) but worked :)

  14. Joe Ladendorf

    Hi. Great article. I just wanted to correct one little thing. The north Star is actually the last star in the tail of the little dipper. It can be found by drawing a straight line through the 2 outside stars of the big dipper. That will point towards Polaris. Thanks for the great article!!

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