A step-by-step guide to night sky photography

The night sky must be one of the Earth's greatest natural phenomena, made all the more special by its status as one of those aspects of nature over which humankind can have little influence. 

All we can do is disrupt its beauty with satellites and make it nearly invisible through our light pollution.

For millennia humans have tried to capture the beauty of the night sky through art. Since the advent of photography, countless photographers have attempted to do the same, mostly with little success.

In the past 10 years, improvements in digital cameras and image processing software have made night sky photography more or less feasible, although it remains something of a technical challenge.

This article outlines the fundamental techniques needed to photograph the night sky successfully.

Let's start with an introduction, finding out what to point the camera at and when.

 

Timing and conditions

In the 'What, When and How' story of night sky photography, this article looks at photographing general views of the sky along with the Milky Way.

Learning when to shoot night skies encompasses several general principles, which include:

• photography is only possible once it has become well and truly dark
• night sky photography doesn't work well when there is a moon, and its bright light dims the stars
• photography is generally only successful during a new moon, at times before the moon has risen above the horizon or after it has set
• the sky must be clear with little to no mist or haze

A final important basic factor is light pollution. In our modern illuminated world, this is one of the biggest enemies of good night sky and star photography, the presence of even relatively small areas of artificial light greatly quenching the visibility of the stars.

Starting with these basic principles and then using the more specific techniques described below, you should be able to photograph a range of night sky views. Particularly wide-angle scenes take in various constellations and the Milky Way.

The latter is a hugely popular phenomenon to photograph among astrophotographers, frequently shot with some well-known terrestrial landmark in the foreground. 

However, capturing such a scene is not a straightforward process. In the Northern Hemisphere, the Milky Way is quite high in the sky during the summer months.

Unfortunately, this also coincides with rather short and not very dark nights, making photography very difficult. 

Through the autumn, things improve, with the Milky Way visible in the southern or southwestern sky as soon as it gets dark. However, as the autumn progresses, it sinks lower in the sky, though the ever-earlier nightfall partially compensates for this. 

As a result of light pollution, just about any urban dweller must travel some distance to find an area with a truly dark sky. So widespread is this problem that a network of International Dark Sky Reserves has been declared, covering places scattered across the world. 

This includes parts of Exmoor, the Brecon Beacons, Snowdonia, and the North York Moors National Parks in the UK. In these places, you can be reasonably assured of genuinely dark skies and, on clear nights, bright stars, including the Milky Way.

Related: How to become a professional photographer

 

Night sky photography techniques

Once you have researched the what, when, and where of your planned night sky photography, there remains the challenge of capturing the images. 

The principal problem, of course, is the incredibly low light levels involved, necessitating the use of long exposures and high ISO settings. Unfortunately, both have a very unwanted side-effect: digital noise. 

This graininess in the final image decreases resolution and can even add in artefacts such as white 'sparks' that can closely resemble stars.

The next technical challenge is that the Earth is rotating, giving us the illusion that the stars are moving across the sky, rotating anti-clockwise around the always stationary Pole Star. 

If you're aiming to produce images in which the stars are sharp pinpricks rather than blurred oblongs or streaks, then unless you take special measures (see below), your exposure times will be seriously limited. 

Many of the techniques used in night sky photography aim to boost the amount of light being received by the sensor while simultaneously minimising the amount of digital noise and keeping the stars as sharp pinpricks rather than blurred lines. 

While much can be done in-camera at the time of shooting, in-computer post-photography processing plays a big part in helping to optimise solutions to all these issues.

 

1. Equipment and getting set up

The night sky photography described here can be undertaken with mostly standard photographic equipment. You only need:

• a DSLR or mirrorless camera (with manual exposure settings)
• a wide-angle lens
• a sturdy tripod
• a remote shutter release

You should also carry a good torch and spare batteries.

A star tracker is one specialised piece of equipment that many astrophotographers use. This piece of equipment fits between the tripod head and the camera base. 

Once it has been correctly aligned with the Pole Star, it will slowly move the camera in synchrony with the Earth's movement, ensuring that the stars remain stationary in the image view and are exposed as perfect spots of light, not trails. 

This will allow you to use much longer exposure times than would be possible otherwise. That said, the star tracker is not essential, and there are ways around the problem of star movement, as we will see.

 

2. Setting the camera up 

Since you'll be working in almost complete darkness, preparing the camera beforehand in good lighting is important. Then, you can try the following steps. 

Set the camera to shoot in RAW format (rather than JPEG), as these files give you the maximum flexibility for the all-important post-photography processing. Then, set the camera's exposure setting to 'manual'. 

Turn off the lens' autofocus mechanism and set the focus to infinity. If necessary, check where the infinity focus is for your lens and then mark it on the lens barrel. If using a zoom lens, set it to the shortest focal length. 

Set the lens aperture to its widest. 

Initially, working out the right exposure is a bit of guesswork, so try ISO 2000 with an exposure time of 15 seconds. Unless you're using a star tracker, you don't want your exposure time to be so long that the stars come out in the images as rectangles. 

The shorter your lens' focal length, the longer the exposure you can get away with, which can be tested using the '500 rule'. Simply divide 500 by your lens' focal length, and the answer is the maximum exposure time in seconds.

If your camera has long exposure and high ISO noise reduction facilities, then make sure they are switched on. This will greatly help reduce the noise levels.

Once you're on location, set the tripod and camera up, and then check that all the settings are still correct. It's likely that the focus at least will have changed. 

Set up your remote shutter release: You don't want to press the shutter button with your finger as this will cause camera shake. You'll need to use a torch for these steps but switch it off before you start to shoot.

Related: Drone photography: shooting from the sky

 

3. Getting the shots 

Line up the composition you want to have, either consisting simply of the sky or (more usually) containing a foreground landscape element. 

If your camera has an optical viewfinder, you may well find that you can see almost nothing through it. Use of the LCD digital viewer is likely to be much more effective in helping you create the composition. 

Press your remote shutter release and wait for the image to expose. If your camera's long exposure noise reduction facility is switched on, the camera will take another 'dark field' image once the image is exposed.

This records the sensor's noise patterns, an exposure that will take the same amount of time as the image exposure. 

Once the dark field exposure is complete, you'll be able to examine the resulting image. Do this without moving the camera. Zoom in to check the shape of the stars: if they're rectangular, you'll need to reshoot with a shorter exposure time. 

Similarly, you'll need to reshoot with a higher ISO if the image is too dark. If the image is over-exposed, reshoot with a lower ISO, shorter exposure time, or a narrower lens aperture. 

This single shot may be sufficient to produce the final image you want once it has been processed on the computer. However, if you intend to maximise contrast, minimise noise, and sharpen the stars as much as possible using specialised star photography software, you should continue shooting. 

Shoot at least 10, but ideally around 30 or more identical images. These will be used for later in-computer image 'stacking'. 

Once you have finished shooting these images, shoot another 10-30 images with the lens cap on. These images will record only the noise the camera's sensor generates. 

While the camera's own noise-reducing programmes should be quite effective, most computer star processing programmes like to have additional dark field images to reduce noise. 

If your view contains any land and especially a foreground element, take a final shot simply of this landscape component, but without moving the camera. This may be needed in post-photography processing.

 

4. Photographing star trails

All of the preceding has assumed that you want to shoot the night sky with the stars as pinpricks of light. 

There is, however, another technique that involves using long exposure times to deliberately blur the stars into long curving light trails. This is particularly effective if you have the Pole Star in the image composition, showing the trails rotating in a circle around that spot. 

The general methods you need to use are similar to the above, except that you'll shoot with the camera at a standard ISO setting of 100. It is possible to shoot such a scene as a single image, with an exposure time of at least 30 minutes, though more likely up to an hour. 

However, while high ISO noise won't be an issue, long exposure noise certainly will be, as will noise generated by heat—the camera can get quite warm during such a long exposure, generating its own noise.

This kind of image is shot as a series of about 100 30-second exposures, each shot in quick succession and then stacked in a star programme.

Related: The ultimate guide to long exposure photography

 

5. Post-photography processing

In-computer processing of the images following the photography is usually critical to the success of night sky and star photography. The principal aims of the processing are:

• to boost the brightness of the stars against the darkness of the sky (in essence, increasing contrast)
• to render the stars as pinpricks of light rather than blurred rectangles (unless the shoot has been to create long streaks of moving starlight)
• to minimise the digital noise from long exposure times and high ISO settings

As already mentioned, the first step to maximising the success of the processing is to shoot the images in RAW format rather than JPEG, giving maximum flexibility in image processing.

If you have shot just a single image of a night sky view, your main processing will consist of running the RAW file through your chosen RAW converter. Examples include Adobe RAW (included with Photoshop and Lightroom), Capture One Pro, or Affinity Photo. 

In this software, you'll be able to do most of the major actions needed to optimise your image, including: 

• brightening
• increasing contrast
• removing vignetting
• changing colour balance
• sharpening and decreasing noise

Such an approach may well generate perfectly good images, though they may struggle to bring out the best in some views, especially the Milky Way. 

It is often felt that it is much more effective to take multiple shots and then stack and blend them to produce a high-contrast, low-noise final single image. 

If you have used a star tracker to move the camera in line with the stars through successive shots, then the stars will be in the same location in every image. This will make it possible to stack Tiff or JPEG files (after conversion from RAW) simply in Photoshop or Lightroom. 

However, if no star tracker is used, the camera will be stationary, and the stars in each successive image will be in a slightly different position as they track across the sky.

Stacking the images so the stars align correctly to produce single pinpricks of light requires specialised night sky processing software. 

Several are available, including Deep Sky Stacker, Sequator, StarStaX and Astro Pixel Processor. All of these will align the stars for you and greatly reduce the background noise by using dark field images that you will have shot at the same time as the sky photography. 

All this works fine, provided your images are simply of the sky. But there will be a problem if there is any land in the image. In aligning the stars in the image stack, the landscape is now out of alignment in each successive image and will come out blurred in the final blended image. 

Some programmes, such as Sequator, have a 'freeze ground' feature that maintains the landscape's position while aligning the stars, thus ensuring that the entire image is sharp. 

If the software does not have such a feature, then after your stack of star images has been blended into a single image, you paste over it the single landscape view you shot at the very end of your photography session. This replaces the blurred landscape with this sharp version.

Related: Neutral density filters for photography: turning down the light levels

 

Pulling it all together and getting started

You're not alone if all this sounds too much to cope with. It does take some time and practice to get all the steps correct. Initially, concentrate on:

• researching the night sky
• when and where to shoot the night skies
• how to work in the dark
• perfecting your photographic skills, shooting just single images
• working on basic post-photography processing skills

Once you've mastered these principal steps, work up to the stacking techniques and the processing involved later. 

Happy shooting and I hope you end up with some wonderful night sky images!

This blog was written by Nigel Hicks, a hugely experienced Devon-based professional photographer. Nigel works with the USA's prestigious National Geographic Image Collection, among many other bodies, and is a Fellow of the British Institute of Professional Photography.

Nigel runs regular photography workshops in southwest England. To find out more about these, go to https://www.nigelhicks.com/photography-workshops-courses/.

To learn more about Nigel's work in general, feel free to take a tour of his website at www.nigelhicks.com.

 

Specialist camera insurance with Ripe Photography

Photographing the night sky is exhilarating, but it doesn't come without risk. That's why you may want to protect your camera through specialist insurance. 

At Ripe Photography, we arrange theft and accidental damage cover up to the value of £30,000 for portable equipment you use when shooting on location and up to £60,000 in total. 

You'll also benefit from EU or Worldwide cover as an optional extra, so your equipment is covered against theft and accidental damage while travelling. 

Click here to discover more about specialist camera insurance, or hit the button below to get an instant online quote today.