Beginners Guide to Deep-Space Astrophotography
The Andromeda Galaxy, taken and processed with close to 4 hours of data
Getting into astrophotography can be a daunting money pit. I’m here to tell you it is just that! Despite this, its not impossible to get into this field of photography and you can start with your basic camera gear tonight.
Astrophotography is a fun endeavor, it gives you a chance to truly learn about the stars and constellations and will keep you up at night. It will be something you’ll spend lots of your free time on, but won’t fail to be rewarding. I’ll be talking about the ins and outs of beginner’s astrophotography and how you can start in this field as someone who spent lots of time researching the subject and performing the act.
To give you an overview of deep-space astrophotography, the process starts with taking a few hundred photos or so overnight of the same object in the sky, say the Andromeda Galaxy. Then taking these photos into a desktop app and “stacking” all of the photos you get, combining them into one super high definition photo with large dynamic range. After, you put it into another app like Photoshop and pull the data back out to reveal the photo in its full glory, editing it accordingly.
The Gear
To start, this guide will be focused on deep-space astrophotography. If you’re looking to do more wide-angle shots of the milky way, this will entail a different procedure. For deep space, the basic equipment consists of: a sturdy tripod, an intervalometer/remote shutter, a DSLR camera, a telephoto lens, and a star tracker.
Tripod
Having a good tripod tends to be an overlooked part of a lot of beginner astrophotography setups. The $10 plastic tripod likely won’t cut it as cheap and light tripods will be too sensitive to motion shake, which is detrimental when taking long exposure photos at 250mm. I started with a Coman DV1000, though marketed as a video tripod, worked great on an astrophotography setup due to its size and weight. Likely any tripod over $70 will work well enough for a beginner setup, though I would opt for the heavier tripods rather than the light travel tripods if possible.
Intervalometer
An intervalometer or a remote shutter is used to automate the picture taking process overnight. You can set it up to automate your camera to take, say 300 one-minute photos overnight giving you effectively 300 minutes of “data” or about 5 hours of data. You can also use it to take photos without physically touching your camera when doing test shots, as to not induce any minor shake into the long exposure photo. There’s many on Amazon and other dedicated photography commerce sites; they all work and essentially do the same thing.
Camera
Most cameras will work for this. Many people like to use older DSLR’s like the Canon Rebel T7i as you don’t need an expensive camera for this to work. Along with this, many people like to modify their cameras by making them full-spectrum, which usually involves taking apart pieces of the sensor and sometimes replacing them with filters and such dedicated to pick up a broader spectrum of light which can be very fruitful for astrophotography. You can do this conversion yourself, or there are websites and servicers who will modify your camera for you for a fee. I never have had my camera astro-modified, and was still able to take some stunning photos. That being said, an astro-modified DSLR is a huge step up from your regular camera. If you ever went further into this hobby, you can get a dedicated astrophotography camera which can really up your game, though I definitely wouldn’t recommend going this route as a beginner.
Telephoto Lens
Many telephoto lenses will work for deep-space photography. I’d recommend a range between 100mm and 300mm for beginner photos, as that will cover most deep-space objects. If you get a variable focal length telephoto, make sure it doesn’t have any bad lens creep, where the lens will slowly zoom in or out due to being pointed up or down as this can make post processing more difficult. If you find yourself liking the hobby after starting, a quick step-up to upgrade your kit without breaking the bank is by getting a dedicated astrophotography telescope lens. Williams Optics makes a great refractor telescope called the RedCat 51 set at a 250mm focal length. Many other brands have similar lightweight telescope lenses for astrophotography that are great ways to quickly upgrade your astrophotography setup.
Star Tracker
The most integral part of an astrophotography kit is the star tracker. A star tracker points to the North Star Polaris to fixate it to an unmoving point in the sky, and slowly rotates your entire camera setup to the motion of Earth’s spin, matching the rate at which the stars move across the sky and removing trailing stars in your photos. If you’ve ever taken a long exposure photo of the stars, you’ll see that the stars will begin to trail, or streak, across your photo. Star trackers eliminate this so you can take longer exposures and collect better data. All that being said, some of my first few astro photos I took were taken without a star tracker. It can be done, but it’s hard to do well and is a lot of work. You can do this by taking short exposures that don’t induce star trails on your tripod, and recentering your camera to stay pointed at your subject every few minutes or so as it will continue to move out of frame due to Earth’s spin. I quickly upgraded to a star tracker and went with an iOptron Skyguider Pro with iPolar which definitely kicked my photos up a notch. Another great option is a Sky-Watcher Star Adventurer 2i Pro. One thing to note with these star trackers is that they have low payload capacities, meaning if you begin to upgrade your setup to have heavier equipment attached to your camera, you will need to upgrade your star tracker to be able to support your increased payload.
The Pleiades, a star cluster in the constellation Taurus
Photo Taking
You’re going to have to take some time to setup your gear. I’d recommend doing this before the sun goes down as its much harder to do without any light, and then just returning to your setup once the sun has totally set to begin your photos.
The basic astrophotography setup will start with your tripod, then mounting your star tracker to the tripod, attaching your camera to the star tracker, and plugging your intervalometer to the camera. Make sure to use the weights on the star tracker to counter the weight of your camera setup, balancing your kit to make sure it tracks evenly. When its night, you’ll want to begin by aligning your polar scope which will be built into your star tracker, to the North Star. This is to ensure your tracker tracks the stars properly, as a misaligned polar scope can cause your photos to not turn out right. With the iOptron Skyguider Pro with iPolar, it had an electronic polar scope. This essentially meant that instead of looking through the scope and eyeballing the alignment, I would hook up my star tracker to my computer and with their program, it would show me the stars electronically and from there I would align it with electronic precision. I found the iPolar to be very good at what it did as I was rarely misaligned, though it did induce a learning curve which took me a lot of fiddling with to get used to.
After polar alignment, you will then have to focus your camera on the stars. For this, autofocus won’t cut it. Start by finding the brightest star in the sky and pointing your camera at that. For focusing, many like to use a Bahtinov mask which is a little cover you put over your lens to help you nail your focus. They can be bought for cheap, or you can make one yourself with some online guides. You can still focus without one, though. For this, while in manual focus and pointed at the brightest star you can find, spin your focusing ring until the star is as “small” as possible. Usually, when you nail the focus, other small stars in the background will show up through the camera as well. Once focused, you’ll want to adjust your camera on the tracker and now point it at the object you want to photograph. I like to use a night sky app on my phone to help with this. For many objects, they’re difficult to see with the naked eye so it may take a lot of adjustment and test shots before you center the object in your frame. Once centered, you can turn on the star tracker to begin the tracking.
With your camera in bulb mode, set your aperture as fast as your lens can go, likely around F/2.8 - F/4. Your ISO should be somewhere between ISO 400 - ISO 1600. Typically, I kept mine around ISO 1600, but this can change case by case depending on the amount of light you need for your shot. Your shutter speed will be determined by what you set on your intervalometer, which is up to you to decide how many shots you want. For more information on this, check out Manual Camera Settings and the Exposure Triangle.
Set up your intervalometer to the desired settings, making sure the photos will be finished by the time the sun comes up or earlier. In my case, I had some trees around me where I often set up my equipment so I would gauge when my subject would go behind the trees with the night sky app and have my intervalometer take photos up until that moment so I didn’t have to cull through the photos afterwards and pick out the bad ones. Start the intervalometer with your camera set to the desired settings, and let it run through the night.
The Milky Way
Stacking and Editing
Post-processing can be and likely will be the most challenging part of astrophotography. You’ll need two different applications: a stacking software and an editing software.
There’s lots of different stacking software that you can try; I personally found DeepSkyStacker to be the easiest to use for me, along with being free. Siril and Sequator are two other good softwares that I’ve tried and are widely used. Stacking essentially works by combining all of the data of your photos into one large photo. If you took 500 photos 20mb each, your stacked photo will be one photo that’s about 10gb. All the data will be compressed into one image making your deep-space photo very high quality.
When the photo comes out of the stacker, it’ll likely look very lackluster for a 10gb or so photo. That’s where editing comes into play. You’ll want to take the photo into an editing program of your choice. Many like to use Photoshop for this, but some others are Affinity and PixInsight which are also very good options. Editing astro photos is a very complicated process and not something that can be explained through a blog post, but the basic process is pulling the data out from the “levels” and histogram. All the data will likely be stacked on top of each other on the left side of the histogram, and you will “pull” it over and over again to the right to spread the data out over the histogram and even out the levels. There are many great videos on Youtube going over this process, and this will take a lot of practice as it isn’t like typical photo editing.
Final Thoughts
Astrophotography can send you into a rabbit hole very fast! One thing will quickly lead to another. You need to track the stars more accurately for longer exposures? You can get an autoguider to keep the stars aligned better. You need a proper telescope or maybe two so you can capture deeper sky objects? Now you have to get a better star tracker to support the weight of a larger telescope. Now the DSLR isn’t cutting it? You get a dedicated astrophotography camera. It’ll send you spiraling with more equipment and money. Despite this, I think out of all types of photography, astrophotography is the most rewarding and interesting. Do the research needed and work with the equipment you’ve got!
