Have you been inspired by beautiful images of the Milky Way or other celestial objects and wondered whether you could capture similar images too? As you’ll see in this astrophotography for beginners guide, photographing the night sky is easier than you might think and, equipped with a modern DSLR or mirrorless camera, it’s possible to capture stunning images with just a little know-how.
Astrophotography is an umbrella term covering different genres, including deep-sky, planetary, solar, lunar and landscape photography. For the purposes of this article, we will look at landscape astrophotography, which is the most accessible and affordable of these disciplines.
Collecting light is king in landscape astrophotography and the more of it you can collect on your camera’s sensor during a long exposure, the better your results are likely to be. So how do we go about collecting that all-important light from faint objects in the sky? The following tips will provide guidance on maximising the available light and will give you the basic knowledge and skills to get started in the world of astrophotography.
Ideally, you’ll be using a DSLR or mirrorless camera in Manual mode. Full frame cameras will perform the best in low light situations as they have a larger sensor and will therefore capture more light. However, modern crop-sensor cameras are very capable for astrophotography and are a more affordable option than full frame cameras.
A wide or super-wide angle ‘fast’ lens in the 12-35mm range is best suited to landscape astrophotography. Wide-angle focal lengths allow you to capture a good portion of the night sky as well as some of the landscape for foreground interest. A ‘fast’ lens is one that has a large maximum aperture – in other words, a small f-stop number. A lens with a maximum aperture of f/2.8 or lower is considered to be a fast lens and is excellent for astrophotography.
A lens like the Rokinon (Samyang) 14mm f/2.8 is a great lens to get started with and is very affordable. If you don’t have a fast lens just yet, you can still use the kit lens that came with your camera. Just make sure you operate at the maximum available aperture size (typically around f/4 on stock kit lenses).
Astrophotography involves taking long exposures, so a sturdy tripod is one of the most important items of equipment. If your camera moves at any point during a long exposure, your image will not be sharp, or worse, blurry. Camera movement from the wind will quickly ruin an image so a solid base for your camera is a must.
Keep your hands free to operate your camera by using a headlamp at night and, if possible, use the red light mode (if it has one) to preserve your night vision. A headlamp is also helpful for ‘light painting’ objects in the foreground of your images.
Remote Shutter Release (recommended)
This will allow you to trigger your shutter while minimising the risk of introducing vibrations. If you don’t have a remote shutter release, use the timer delay on your camera to ensure there is no movement of the camera during an exposure.
It may sound obvious, but you’ll need to be in a dark sky area to be able to capture detailed images of the night sky. Head away from urban areas and find a dark sky location with minimal or no light pollution. There are useful websites like Dark Site Finder and Light Pollution Map, which will help you to find a suitable location to shoot.
The night sky is constantly changing throughout the year and knowing what you are going to photograph is a key component of astrophotography. There are excellent apps like Stellarium and Starwalk 2 which allow you to visualise how the night sky will look at any time and date for a specific location.
We’ve covered the gear and the planning so now it’s time for the business end – taking the shot! Camera settings will vary slightly depending on the ambient light of the location and focal length but the following information will give you a good starting point to work from.
Manual. You will need to set the shutter speed and ISO manually.
Image File Type
RAW! Astrophotography can be broadly split into two separate areas – photography and post-processing. In order to process your newly acquired astro images back at home, you will need to shoot in RAW so that you capture and retain as much data as possible.
The aim is to capture as much light as possible while at the same time avoiding noticeable star movement in the image, known as star trailing. The longer the focal length of your lens, the shorter the shutter speed will need to be in order to avoid star trails.
So, how do we calculate the correct shutter speed for any given lens? We use a formula called the ‘500-rule’. In its simplest form, this is 500 divided by the focal length of the lens you are using. For example, if you are using a 20mm lens, this would be 500 / 20mm = 25 seconds. This, however, only applies to full frame cameras. For a crop sensor camera, the crop factor needs to be taken into account, so in this instance I would recommend using a base value of 300 for your calculations (for APS-C type cameras).
Open your aperture to at least f/2.8 if your lens allows (or the lowest f-stop possible). You want to capture as much light as possible during your exposure.
The higher the ISO, the more the light signal is amplified from your camera sensor. You will need to shoot at a high ISO but there’s a trade-off. The higher the ISO, the more noise (a type of digital degradation) you will see in the image. ISO 3200 is a good starting point. You may need to adjust down to something like ISO 1600 if there is a lot of ambient light or light pollution. Very dark skies may require you to boost the ISO to 6400, but I wouldn’t recommend going higher than this.
Focusing in the dark
First, set your camera to manual focus – autofocus will not work in the dark. Then use the ‘Live View’ feature of your camera to display an image preview on the camera’s LCD screen. Identify a bright star or distant light source like a streetlight on the LCD display and digitally zoom in to that point of light. Once you have done this, adjust the focus ring until the star or light source becomes as small as possible. Your focus is set!
Now all you have to do is to compose the frame, take the shot and wait for the image to pop up on the LCD display! If your foreground is looking dark, try light ‘painting’ your subject with a headlamp or your smartphone light during the exposure to help brighten the scene. You may need to adjust the ISO or aperture slightly to find what works best for your location, but you are now firmly on your way to capturing your own images of the beautiful night sky.
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