Beginner deep-sky astrophotography with a DSLR for real results!
By Trevor Jones
First off, let me explain my situation. Like many of you, I am a pretty busy guy. I work 9-5 each day and weekends are usually filled with social commitments and family gatherings. This does not leave a lot of time to spend outside in the dark photographing deep sky objects in space!
Add in the fact that the weather needs to cooperate as well, and you’ve got a very limited window in astro-imaging time. Making the most out of this limited window of imaging time is important! The last thing you want is to spend your one CLEAR night in the backyard fighting with your equipment, and ending up empty handed with no images to show for your efforts.
The basic process for capturing deep-sky images is this:
- You shoot multiple, long-exposure photographs with your DSLR through a tracking telescope.
- You then combine the images together to improve the signal to noise ratio.
- Image processing is then needed to bring out the fine details in the object, and correct the levels (brightness) of the image.
The quality of the final image depends on many factors including the level of accuracy your telescope is tracking, focus, and using the best camera settings based on your location.
The best way to learn how to get better is by experiencing the process for yourself. Each night of astrophotography will remind you of the small nuances of your equipment. Eventually you will understand exactly where your camera needs to be for perfect focus, and how to properly balance your gear.
It’s all about paying attention to what works, one step at a time. If you do that enough times, you’ll have a system that takes you to the finish line time and time again.
Let me tell you exactly what has been working for me for the past 6 years, and how I have been able to capture over 50 deep-sky objects with an entry-level, basic DSLR deep-sky imaging setup.
Capturing photos of distant galaxies and nebulae is reserved for those who are able to track the apparent movement of the night sky. This also means using a DSLR to take long exposure photographs through a telescope. Below, I’ll cover a basic deep-sky imaging setup that will provide you with more photos than it will headaches.
I enjoy shooting with Canon DSLRs, specifically in the entry-level Rebel series. My first DSLR was a Canon 450D (Xsi), followed by a Canon 600D (T3i). Modifying your DSLR can improve the amount of certain types of nebulosity in your images, but it is not
necessary right away.
These cameras are widely available in the used market, and provide reliable results for an affordable price. If you want to get started in deep-sky, do yourself a favour and start with a Canon Rebel series DSLR.
I always recommend that beginners start with a wide-field refractor telescope for astrophotography. They have several advantages over larger telescopes of a different design:
- They are lightweight and portable
- They do not require regular collimation
- They offer a forgiving wide field of view
If your budget allows for it, spring for an apochromatic refractor. This type of telescope will produce better photos due to the extra low-dispersion glass used. The stars in your photos will not suffer from chromatic aberration as an achromat would. The shorter focal length of a small refractor will produce beautiful wide field images of deep-sky objects in space. This means that large objects such as the North America nebula and California nebula are within reach. I use a 102mm apochromatic refractor (triplet) that offers an extremely flat field of view. It captures crisp, high contrast images with no chromatic aberration.
A German equatorial telescope mount is required for astrophotography. These mounts can be polar aligned to move move in the exact motion of the night sky. This effectively “freezes” the objects in space so that you can photograph them. It is often said that your mount is the single most important part of your astrophotography equipment. To accurately track the stars and deep-sky objects among them, your telescope mount needs to be sturdy and reliable.
Keeping the camera absolutely still with a consistent, fluid motion is essential for astrophotography. It is important to select a mount that is rated to carry the weight of your telescope, and all astrophotography accessories. It is wise to “over mount”, meaning to choose a mount that can easily support a heavier payload than you currently own. This way, the mount will move effortlessly as it tracks the sky.
I use an affordable astrophotography-rated GEM (German Equatorial Mount) that is well-suited for my current imaging equipment. This mount happens to be quite popular, so there are a number of aftermarket mods available. Upgrades for both the software and hardware have been developed to help my Sky-Watcher HEQ5 perform better than ever.
The Camera, Telescope and Mount are the 3 main pieces of the puzzle, but there are a few extras needed to get everything running smoothly. It’s all about keeping the DSLR and telescope locked onto the deep-sky target for as long as possible.
A guide scope is used for autoguiding the telescope. This is a smaller telescope that rides on top or next to your primary imaging telescope. It’s job is to focus on a star within the field of view, and use it to keep the mount “guiding” on that area of the night sky. This can only be done by using a camera for this purpose only. I use a small Orion 50mm guide scope that adds minimal weight to my overall imaging payload.
The guide camera peers through the guide scope to display an area of the night sky. Then, we’ll use software to choose a star within that area and “lock on” to it. These cameras are usually much smaller than the imaging cameras. They collect “signal” in the form of star light, and provide a looping “live-view” of the sky. I use an old CCD camera made by Meade known as the Meade DSI Pro II. When connected with my 50mm Orion guidescope, the system works very well for my autoguiding needs.
To control the camera and set it to capture images throughout the night, a basic Windows laptop is used. This allows you to control things like:
- Automatically shooting the exposures
- Running the autoguiding camera
- Adjusting the frame and focus of your image
- Testing different exposure lengths and ISO settings
It is much more enjoyable to control the camera and review settings using the computer screen rather than on the back of the camera! It allows you to fine-tune the focus and framing of your target with much greater precision.
A field flattener is an adapter that you place between the camera sensor and the telescope, to “flatten” flatten the field of view. Depending on the type of telescope you use, the stars at the edges of your image frame may become elongated or “football” shaped. With the right field flattener adapter, the stars in your images with be round pinpoints right to the edge of the frame.
Throughout the night, the temperature can drop. When this happens, moisture can collect on the objective of your telescope. This effectively “blurs” your images as the moisture obscures the view through your telescope.
To combat this, astrophotographers often use a dew heater strap around their telescope. This heated velcro-strap gets warm enough to keep your telescope dry, much like the defroster does in your car.
It may seem like a lot of equipment to purchase and learn how to use. But with patience, you’ll learn how to best use each item and improve your astrophotography images. Talk to others about what they are using, and view the results they are getting for a better idea of what to expect. I feel that the system explained above is a real winner in terms of hassle-free results.
The other half of the equation is image processing, and the folks here at PhotographingSpace.com can definitely help you out with that! It is a great time to be an amateur astrophotographer, as there are countless astrophotography tutorials available online.
I have put together a few tutorials on YouTube myself, so feel free to check out the AstroBackyard YouTube channel for more.
Until next time, clear skies!
About Trevor Jones
Creator of the AstroBackyard community, Trevor Jones photographs the night sky from his backyard in St. Catharines, Ontario. Trevor is an active member of the Royal Astronomical Society of Canada, and provides talks to photography groups about DSLR deep-sky astrophotography.
Trevor is marrying his high-school sweetheart and biggest fan, Ashley in December 2017. Together they make sure their lab/hound mix “Rudy” gets plenty of walks and attention.