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Published 13th March 2021

Night Sky Photography

Bright Milky Way over the lake at night (panoramic photo)

Camera Gear for Night Sky Photography

Firstly, the quality of the camera you use for night-sky photography makes a huge difference to the quality of shots you ultimately get. The reason is the quality of the camera's sensor. As a general rule of thumb, the larger the camera's sensor, the more light it will collect. The more light the camera can collect, then the higher the image quality will be.

So, the best consumer cameras for night sky photography are full-frame. It used to be the case that DSLRs were the best option, but some of the newer full-frame mirrorless cameras also get great results. Here are a couple of examples that work really well. If you don't have a full-frame camera though, you can still get perfectly acceptable results.

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The Canon EOS R is a full-frame mirrorless camera with incredible low-light performance. Canon also has an EOS Ra model dedicated to astrophotography and includes a built-in infrared filter. However, unless astrophotography is the only thing you are going to photograph, then the EOS R is a better option, as you can add an infrared filter as an accessory on your lens.

The Canon EOS 5D Mark IV enjoys superb image quality, whatever you are photographing. From street reportage to location portraiture and landscapes in the evening light, the camera captures incredible detail, even in extreme contrast.

Lens Options for Night Sky Photography

If you want to capture that big expansive feel of the universe, then the wider your lens the better. Of course, if you don't have a super-wide lens, then there is no need to rush out and buy one! Use the lens that you have. Anything below about 25mm is going to get you great results. Also, because we want to maximize the amount of light getting to the camera sensor, it stands to reason we ideally want a nice fast lens. Here are a couple of options.


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Suitable for Canon Mirrorless or DSLR, the EF 16-35mm f/2.8L III USM is an ultra-wide-angle lens producing stunning clarity throughout the focal range. Ideal for astrophotography, the focal lengths this lens can achieve make it an ideal companion for wider perspectives.

Designed for Canon Mirrorless Cameras, this lens offers exceptional flexibility even in low light. This L-series RF lens is ideal for astrophotography thanks to its superb wide-angle quality and 5-stop Image Stabilization; producing clear and dynamic angles even in tight spaces.

Camera Accessories for Night Sky Photography

A tripod is a requirement for night sky photographs, due to the need to take long exposures of anything up to about 30 seconds. There are hundreds if not thousands of options out there that you can use, but do go for something sturdy. Also, go with something that has an optional hanging hook on the tripod pole to weigh the tripod down. This will help to avoid any expensive accidents

Remote Shutter Release

To avoid shaking your camera when you take a shot, a remote shutter release is a great little accessory. You can either have a mechanical shutter release, or a nifty option is an electronic remote shutter release.

An electronic shutter release allows you to stand well away from your camera and tripod whilst you take shots.

Light Pollution Filter

Unless you are living far away from light polluted areas, a clear-sky filter will help to filter out specific wavelengths associated with light pollution. The result is more true to life colors, increased details, and contrast captured in-camera.

Gaffer Tape

Gaffer tape is useful for a couple of things when photographing the night sky. When you have focussed your lens, it is useful to stick a piece to the focus ring and lens body. This stops you from accidentally knocking the camera out of focus, particularly when working in low light. Also, if you have a DSLR, then putting a piece on the eye-piece will stop light creeping. The great thing about gaffer tapes is it doesn't leave a sticky residue.

Powerful Flashlight

As well as guiding your footsteps, a powerful flashlight is actually a really good piece of equipment for acquiring focus with your camera. More on this later in the article.

Preparation for Night Sky Photography

Staying Safe & Warm

Next, is to ensure you have the right non-camera-related kit for your photo-shoot. Make sure you have enough warm clothes in your backpack, a torch, spare batteries, compass, maps, etc with you. Night Sky Photography takes time and patience, and the last thing you want is to be freezing cold; or worse, lost in the desert and in the dark. So your backpack needs to have everything you need to keep warm and safe.

Useful Smart Phone Apps

Luminos

Luminos is a paid App but contains a wealth of useful information. The makers claim it has the most complete library of stars, asteroids, comets, satellites, and moon surface features; of any other smart-phone app. It certainly has a wealth of features for star-gazing:

1) You can hold your phone up to the sky with Luminos active, and its motion-tracking will identify objects in the sky for you. It will even model your terrain with an accurate representation of the earth's atmosphere.

2) You can check flyover times for satellites such as the International Space Station, then follow their paths across the sky.

3) If you have powered up your astrophotography with an equatorial mount, you can use the App to track synchronized objects.

4) Its article catalog gives you access to detailed information on 1000s of objects, wherever you are.

Here is an actual screenshot with planetary IDs and a satellite location identified clearly identified. The App is available from the App store.

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ClearOutside

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Another really useful App, this one a free one, is ClearOutside.

ClearOutside is basically a weather forecasting App. You can set it up for specific locations, and it will tell you sunup and sunset times, the moon phases, percentage cloud cover at different altitudes.

The App even includes details of when the International Space Station (ISS) is visible at your location, as well as other information on visibility, fog levels, and the chance of rain.

Choosing a Location

When choosing a location for Night Sky Photography, you want to pick somewhere that light pollution is at a minimum. A great (free) resource to do this is the website Blue-Marble.de. They have integrated light pollution maps into the Google Maps API, so if you are familiar with Google Maps, then navigation around the Blue Marble Maps is a breeze.


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How to Focus your Camera

Focusing is not as intuitive as you might first think. The immediate inclination would be to set the camera's focus ring onto infinity, and off you go. This is a good start, but it is not necessarily going to give you the sharpest results you could achieve. The reason is the variability and tolerances of different lenses during manufacture.

Automatic focusing is generally out of the question. Unless you are setting up before sunset, there is unlikely to be enough light for yourr camera's sensor to focus for you. So manual focus is the most reliable way to go.

As well as manual focus, you always want to use the center spot in your lens to set up your shot, and if possible, with the focal point at the center of your frame. This is due to the field curvature effect of your lens. This is particularly prevalent on wide-angle lenses, whereby they lose focus towards the edges. By having your focal point in the center, the effect of this is lessened. Plus, the image will also naturally tend to get darker at the edges due to vignetting/darkening at the edges of the lens.

Ok, so we have your focus set to manual and are using the center spot of the lens. Here are some methods you can use to actually set your focus up. Noting these are in order of preference.

Moon

If the moon is somewhere in the sky, and even if you don't intend to have the moon in the shot, it is a useful object to focus on. Either work through the lens or on your live-view panel, acquire focus by making sure that the moon is completely sharp. If you are working on the live-view panel, it can also help to magnify the view. Once focus is acquired, grab a piece of gaffer tape to secure the focus ring to the lens. This will stop everything moving around as you set up for your actual shot.

Distant Objects

If there are distant objects that are lit, for example, buildings, cars, roads, etc; then they make great objects to set focus on. Use the same technique as for the moon. A top-tip, if you have a really strong flashlight, is to use that to light a distant object. Once again, grab a piece of gaffer tape to secure the focus ring to the lens.

Bright Stars

To use this method, pick one of the brightest stars in the sky, and with manual focus and center spot, focus until the star is perceptibly at its smallest. This will indicate it is in focus. Once again, gaffer tape your focus ring to keep everything secure.

Focus Double-Check

Once you have your shot composes, there is a final double-check to make sure you really do have a tight focus. This technique uses the chromatic aberration effect, which you will no doubt have noticed in your images during post-processing. Chromatic aberration is a green or a magenta glow around hard edges and indicates something that was slightly out of focus. Take a look at your composed night-sky image magnified on your live-view panel. If there are green or magenta glows, then tweak your focus very slightly to find the mid-point.

The next thing is to take a few test shots. Are all these checks necessary? Well, there is nothing worse than getting back from a field trip only to find that you didn't get the shot. For this final check, you don't even need to worry about your camera settings. Just take a few shots at a high enough ISO that they are just a few seconds exposure length. Then, using your live-view, zoom into the image on the brightest objects.

Getting the Shot - Camera Settings

Avoiding Star Trails - The 500 Rule

The first thing we need to work out is the maximum exposure length for the lens that you are using. To do this, we use the '500 rule'. The 500 rule is a rule of thumb guideline to work out the maximum exposure time before star trails appear in your image or before stars look blurry.

The calculation works with lenses up to about a 200mm focal length but is most effective for wide-field astrophotography. The 500 rule goes as follows:

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The Focal Length is the focal length you intend to use for your shot. So for an example, let's use 15mm based on the example lenses from this article.

The Crop Factor is based on your sensor size relative to a 35mm sensor. So for an APS-C camera, this would be a factor of 1.5 and for a full-frame camera a factor of 1. Let's then use a factor 1 based on the cameras featured in this article.

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So this means that if we are using a 15mm focal length on a full-frame camera, we can use a maximum exposure length of 33 seconds and still get a nice sharp image. But! This doesn't immediately mean we need to take shots of 33 seconds, this is just a reference point for when we are in the field.

Camera Settings

Ok, our camera is sat safely on a tripod, we have focussed the lens on the scene we want to capture, the camera is connected to a remote shutter release, and based on the focal length we are using, we have calculated the maximum exposure length that can be used. Now:

1) Set the camera to either Bulb or Manual mode.

2) Set the Aperture to the lowest setting for your lens e.g. F4 or below is typical for prime lenses, or F5.6 is typical for a kit lens.

3) Put the camera into the Daylight White Balance setting. The important thing here is that setting the white balance to a constant setting helps when you come to post-process your images.

4) Shoot in RAW image format. This will maximize the number of pixels we capture, and thereby reduce noise to a minimum.

Now, starting with an ISO of 400, take a timed shot using your remote shutter release at say 15 seconds. Then, take a look at what you captured in your live-view panel (not forgetting to zoom in to check details). If your image is under-exposed, then take another shot but with slightly longer exposure and vice-versa.

If you get to the maximum exposure time, and you are still not happy with the exposure, then you need to up the ISO to 600, and start the process again. This also then works in the opposite direction if you need to reduce the ISO, then do so.

The optimum point then is to keep the ISO as low as possible to keep sensor noise down to a minimum and to not increase the exposure time above your 500 rule setting. In conclusion on camera settings, this is a process of trial and error to get the shot, but by following the logical sequence above, you will quickly find the optimum exposure.

Post-Processing Night Sky Images

There is an infinite number of subtleties to how you can post-process your wide-field astrophotography images. But, this is a normalized work-flow using Lightroom Classic and works pretty well for most Night Sky images.

Basically what we are trying to do, is make the stars pop. In respect, post-processing night sky images is a lot different from conventional photo editing. Here is a short video that demonstrates the technique, after which a step-by-step guide.

Histogram


The first thing to recognize when editing a Night Sky photograph is that the histogram will naturally sit at the lower end of the curve towards the shadows and blacks. Trying to specifically target highlights and whites then is not going to achieve much, as the brightest stars are pretty much the only whites/highlights in the image.


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Tone Adjustment

Because we don't have much contrast range to deal with, many people when post-processing these types of images will up the luminance to 100%, edit the color balance and contrast, and then reduce the luminance back to a normal level. There is a better way!

Pressing and holding the ALT key right before you adjust either the White or Black tones in your image brings up a mask. It is then a really simple job to adjust the sliders so that white and black are just peeking through the mask. It's as simple as that!

For night sky photography, I tend to avoid adjusting the exposure unless necessary. The reason is that harsh global adjustments can all too easily start to introduce unwanted noise and/or artifacts into your image.

I also tend to leave the highlights and shadows tone sliders alone, instead, I increase the Clarity, which targets the mid-tones of an image and enhances the sharpness and texture.

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Tone Curve

The next edit is in the Tone Curve. A useful technique here is to pin the upper limit of the midtones and then push the highlights. This enhances the. highlights, but stops the midtones and blacks increasing. This edit is done in Lightroom but a similar technique is to open the image up in Photoshop and stack this edit on multiple layers with the blend mode set to multiply.

The next step is to saturate the colors present in your image to make them stand out more prominently. What color to target depends of course on what you captured. reds and oranges are good bets for many of the nebulas, including Orion & Horse-head. You basically need to play this one by ear. In our case, I targeted just the reds and oranges to demonstrate the technique.

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Hue, Saturation & Luminance

Firstly I set the red and orange Hue sliders down so that our saturation and luminance changes don't look too radioactive. Then increased each of the saturation and luminance sliders for red and orange. Essentially both saturation and luminance are both saturation sliders, it is just that saturation is a global adjustment, whereas luminance is more targetted on colors that are not already saturated. Here are the settings:

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TOP-TIP: When you are processing night sky objects, you can typically push HSL a lot more than with other genres, because night sky images are significantly less saturated, to begin with. 

As a final edit, I added a very small amount of noise reduction. This helps to smooth out any noise and artifacts that might have been introduced during the image processing. You only need a small amount though, too much, and your image will look plastic and washed out.

From the before / after comparison, you can see that the image has a more punchy contrast and that the natural colors in the sky pop. One final thought on image post-processing is masking. Depending on your image, it is sometimes used to use a selective mask to avoid over-processing any landscape portions in your image.

Before:

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After:

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Hopefully, this article has now given you a reasonably detailed insight into this fascinating area of photography. The article only covered wide-field astrophotography and as a single image capture in-camera. If you get seriously into astrophotography, typically photographers will take multi-frame stacked images, using an equatorial mount to track star movement. These devices allow you to take multiple shots and avoid star-trails. 


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