Do you need a special camera for astrophotography?
October 28, 2022
If you are new to astrophotography or want to try it, you might ask this question. Like me, you may have tried to take a picture of the night sky with a smartphone and found that the results are not quite what you wanted. If you have ever tried to take a photo through the eyepiece of a telescope, you’ll know how difficult that is. So, is it necessary to use a special camera for astrophotography?
You do not need to use a special camera for astrophotography. A DSLR camera or even a quality smartphone can be used. DSLR cameras can be modified by removing filters from the sensor to make them more sensitive for astrophotography or used as is. A camera with manual focus and longer exposure is OK.
Having said that you don’t need a special camera to do astrophotography, we need to delve into this much deeper so that you can get something acceptable from your attempts to photograph the night sky. You must be aware of and understand many things before taking an astrophoto you can be proud of.
Also, it is important to point out here that there is a huge difference between the expectations and abilities of beginner, intermediate and advanced astrophotographers. At the start, any camera can be used to take amazing pictures of the night sky, but as we go deeper into this hobby and become better at it, our skills will require more specialized cameras and techniques to improve the quality of our astrophotos. I’ve written this useful page about the best cheap camera for astrophotography – click for my advice.
I first tried using an iPhone and quickly moved to a Canon DSLR and then a dedicated astronomy camera which is cooled. Each of these cameras produced excellent results but as I progressed as an astrophotographer, I needed a special camera for the job as my expectations rose. Click here to discover the best DSLR cameras for astrophotography.
Which camera you can use may also depend on the target you are trying to photograph. Are you taking general night sky photographs of stars or the Milky Way? Or do you want to photograph a combination of targets in the sky against an interesting landscape as your foreground? Or perhaps you want to photograph planets or the Moon? Finally, as I prefer, you may be interested inphotographing deep sky objects such as galaxies and nebulae.
Photographing the Milky Way
Photographing the Milky Way is a joy that is not so hard. You can use a good smartphone or a DSLR camera to take decent shots of the Milky Way. When I took my first shots I attached my Canon DSLR to a tripod and set my camera to manual focus, adjusted it, and started taking 20-second shots. I could immediately see the results on my camera’s LCD screen. You can take 20 seconds or so if your lens is widefield, say 17-50mm but with a lens, with more magnification, you will need to shorten the exposure. The reason why is that as you zoom in on the sky, stars will start to trail more quickly.
Using a smartphone is possible but you need to be able to adjust the settings to get a longer exposure and an ISO that will allow the objects in the sky to appear clearly. Check out this brief guide on choosing the best camera settings for astrophotography that I’ve written for you. Focus is important as ever and the phone must be kept absolutely still so a tripod is best. It’s probably going to be difficult to use an older smartphone as cameras were not so sensitive in the past and resolution was low.
If you plan to include a foreground landscape in your photos of the night sky then it’s probably best to use a DSLR camera in manual focus. You will get a high-quality foreground with this kind of camera but be careful of the settings you use so that you get enough light on your subject. The sky will require longer exposure but should be limited so there are no star trails (unless you want them in your shot). You’ll also possibly need a special app to adjust the camera settings such as your ISO setting and so on.
One of the best ways to image planets is to use video so you need a camera with good video capabilities and a DSLR is ideal for this. You can use a smartphone but it is more difficult to get a good-quality video that will be useful for your subsequent processing to create a final image. Some dedicated astronomy cameras are designed for planetary imaging as they have a good frame speed for video.
Why do we use video for imaging planets? This is because when you look at them through a telescope they wobble and the details are clear one moment and blurred the next. This is because of the atmosphere that moves and obscures details on the planet. Taking video enables software to separate the video into hundreds or even thousands of frames which are then each stacked and a final image of higher quality is the result.
The Moon is a very easy and bright target to photograph. For a high-quality image we take several photos and stack them but you don’t need many, 10 or 12 is usually enough. Your camera needs very good resolution, so only a smartphone with a good camera should be used and your exposure settings need to be adjusted to take the images very quickly because of the brightness of the moon. Take a look at this explanation if you wonder what causes the moon to glow so brightly.
The settings on your smartphone or DSLR will change according to how much the moon is illuminated. I’ve taken great pictures with my Canon 600D!
Deep Sky Objects (Galaxies and Nebulae)
Now we come to probably the most demanding type of astrophotography which is focused on capturing deep sky objects outside of the Solar System, especially galaxies and Nebulae. It is the most difficult because the objects can be millions of light years away and extremely faint. Often these objects cannot be seen with the naked eye and most are not even visible except through a large telescope.
In order to photograph most deep sky objects long exposures of up to several minutes and the use of a special telescope mount that can track the movement of the objects you wish to photograph is necessary. We can use any camera that can be attached to a high-quality lens or telescope and that is capable of long exposure shots for hours at a time. Most smartphones will not be suitable but DSLRs can be used with other equipment such as an intervalometer (a device that connects to a DSLR and enables you to set any length and number of exposures with pauses between them as you wish), in this way your camera can shoot long exposures for hours without supervision.
DSLRs can also be connected to laptop software that will enable a series of images of any length and quantity to be taken and stored either in the card of your camera or on the laptop for later stacking and processing.
Dedicated astronomy cameras can be used and these are very practical as they are easily connected both physically and electronically to your equipment and computer and are very sensitive to the light given off by deep sky objects. These cameras are more specialized because they are designed for astronomical use. Check out more about using a computer or laptop for astrophotography.
Other Factors That Affect Whether You Need a Special Camera for Astrophotography
So far we have said that you do not need, particularly for some purposes, and also especially as a beginner, a special camera for astrophotography. There are, however, a number of factors that may cause you to consider using a special camera to improve your night sky photography. What are some of these factors?
One important factor is noise. Every camera produces noise and this can hide the finer details in your astrophotos. I think this is true for all kinds of astrophotography but especially for deep sky objects such as nebulae where faint details are often hidden in the dust and gases around the target we wish to image. Some level of noise can be removed by creating calibration frames and subtracting them from our photos when we stack them. However, there are random forms of noise, the most important of which became obvious to me whilst imaging with my Canon DSLR this summer. Thermal noise.
Thermal noise can be a big problem if you live somewhere with high temperatures, especially in the summer. Whilst imaging several targets this summer, such as the Wizard Nebula or the Omega Nebula, I noticed that the outside temperature was often 27C and the sensor of my camera was reaching 34C! The result was that my images were extremely noisy and this noise was creating blotches of random colour that made my images very difficult to process.
The way we normally deal with high levels of noise is to stack many pictures together as the noise reduces as we do this. In fact, there is a mathematical formula that says the sign-to-noise ratio increases in direct proportion to the square root of the number of images stacked. So, if I stack 100 images together it should improve the signal-to-noise ratio ten times. This means the more noise we have, the more images I have to stack, and the more time I need to get a good final result.
After a summer of imaging and struggling to get past this problem I decide to buy a new cooled camera. I chose to buy a dedicated astronomy camera by ZWO. I got the ASI533 MC PRO which is a colour camera with a high-quality sensor specifically designed for astronomy that can be kept up to 35C cooler than the outside temperature. This reduces the noise in the photo hugely. In theory, instead of taking pictures in the summer with a sensor at 34C, I can have a sensor taking them at a temperature just below zero.
Therefore, for high-quality deep sky images, a DSLR can be used in the cooler months, but in the summer a cooled camera is best. It is possible to cool a DSLR but this requires modification which is not easy nor as practical as that which is standard on more specialized astronomy cooled cameras.
Astro Modification of Cameras
Usually, DSLRs are designed for daytime general use and so there are filters that stop certain light from getting to the sensor. These include Infra-Red and other wavelengths such as Hydrogen Alpha that are important in astrophotography. Hydrogen Alpha is a wavelength that is very common in the gases of Nebulae and other deep-sky objects. A camera without modification may pick up only about 40% of this wavelength, whereas with a modification and removal of the blocking filters over the sensor it can become as much as twice as sensitive to this light. The result is a much better image.
In this sense, even if you use a DSLR, you should consider getting it modified so it now becomes a special camera for astrophotography.
Smartphones cannot be modified in this way and therefore will not be sensitive to all the wavelengths of light necessary for high-quality deep sky imaging.
Dedicated astronomy cameras do not have the blocking filters that DSLRs do because they are designed to capture as much of the light as possible that we need for deep-sky objects.
Quantum Efficiency of Cameras
As we have seen, to get good images in astrophotography, especially with deep sky objects, we need a long time to image. Therefore, if a camera can capture more light than another in the same time, it will actually save you time by producing a better picture more quickly. Quantum efficiency measures what percentage of the available light a camera can capture as it is imaging. DSLRs typically range between 30-40%, whereas dedicated astronomy cameras range between 70-90% which means these special cameras can actually save time.
As you start this hobby, you will find you do not need a special camera. As you progress and go deeper you will strive to improve your images and this is when a special camera will become necessary. In this sense, you will outgrow your simpler equipment and need more sophisticated tools to get the job done to a satisfactory level. Isn’t that the way it is with most challenging activities and pastimes?