4 Steps to Get Started in DSLR Astrophotography (Beginners)
The first step is always the hardest, and astrophotography is no exception! With a million different setups you can pick from, and tons of complicated choices to make, it is easy to see why astrophotography is one of the most difficult types of photography to do. For that reason I'm writing this post showing you how to get started with astrophotography in four steps:
1. Choosing your gear
2. Choosing your editing programs
3. Finding a place/time to go shoot
4. Choosing the right exposure
Choosing your gear:
If you're just getting started in astrophotography, there are a lot of things you can shoot with relatively inexpensive gear. If you already own a DSLR camera, then you're most of the way there to having a great starter setup. Every astrophotography setup is going to have a couple of key components:
Any camera with manual exposure capability will work well for astrophotography. You need to be able to take long exposures (30 seconds or more), and have control of your ISO and aperture. Full frame or crop sensor cameras work. Bonus points if you have an intervalometer, or some way to expose longer than 30 seconds.
Under the night sky, faster lenses are the best. Ideally f/2.8 or faster for the best results. That being said, you can still achieve some good results using a slower kit lens. If you don't plan on using a tracker, stick to wide angle lenses. If you do plan on using a tracker, you will be free to choose most focal lengths you want.
For long exposures, stability is key. Lots of tripods will do the job, but if you plan on hiking or backpacking with your gear, you may be spending a bit more for a tripod that is both light and stable.
This will be the most important part of your setup. The Earth rotates under our feet rapidly, meaning you will only be able to take exposures at or shorter than 30 seconds long depending on your lens. Getting a cheap tracker will make your astrophotography 1000x better and easier, for this reason I recommend them to beginners. If you want to see how much of a pain it is to shoot untracked, check out this youtube tutorial I made.
This setup may look complex, but still contains all the base elements of a typical setup.
Now that we've laid out the key components, here are some good setups I recommend:
|Camera||Canon T5i||Canon 6D||Canon EOS RA|
|Lens||Canon EF 50mm f/1.8 STM Lens||Rokinon 135mm f/2||Rokinon 135mm f/2|
|Tripod||Radian Tripod||Radian Tripod||Radian Tripod|
|Tracker||Skywatcher 2i Pro Pack||Skywatcher 2i Pro Pack||Skywatcher 2i Pro Pack|
As you can see, there are some things that stay constant throughout my cheap to expensive beginner setups, and those are the tripod, tracker, and camera lens. In astrophotography it really pays to not skimp on the tracker or tripod, this will aid so much in getting sharp long exposures. The main changing factor in a beginner setup is how much you want to spend on a camera body.
For me personally, I use the intermediate setup because I think it provides the best bang for your buck. The Canon 6D is an old but proven astrophotography camera that produces great results. The Rokinon 135mm f/2 is the best lens ever created for astro, and its only $500 so that's an easy pick.
Basically, if you want to eventually use a dedicated astronomy camera, don't go blow $2,500 on an astro-modded DSLR. A $1,000 astronomy camera will run laps around the EOS RA for deep sky, for your beginner setup try to keep it simple. That being said if you have $2,500 to blow the EOS RA is a better option than the other cameras here.
Choosing your Editing Programs:
With all the data you're going to be collecting, you need to have some kind of programs to edit it all. Editing astrophotography images have two main components, preprocessing and postprocessing.
This step is all of the editing you must do to create the initial image that becomes your final image. You will need to calibrate, register, and integrate all of your raw data frames. Calibration is the application of flat, dark, and bias frames. Registration is the alignment of all of your raw frames, and integration is the combination of all registered frames to produce a low noise master image. There are both free and paid programs that can accomplish this:
| Sequator: Free
Sequator is a free google program which is good for preprocessing wide angle images, especially those shot without a tracker. It can also produce star trail images. It is not capable of calibration though, which is an important step.
Deep Sky Stacker: Free
Deep sky stacker is the classic free preprocessing and stacking software. It cannot be easily ran on Mac. It is capable of calibration, registration, and stacking.
Pixinsight is most commonly used and most favored program for all things astrophotography. It has everything you need from preprocessing all the way to postprocessing. It is expensive but has a 30 day free trial you should utilize.
Astropixelprocessor is similar to pixinsight in its function, but with a slightly less advanced interface (which can be a really good thing). It is very powerful for building mosaics, and has an excellent gradient removal tool.
Post processing encompasses everything you do to your preprocessed master image to produce your final result. For example color balancing, histogram stretching, curves, local contrast, and other aesthetic changes. Some of the programs mentioned earlier can perform this task as well. Here are some options:
GIMP is a free Photoshop alternative. It can perform histogram stretches, color changes, and masking operations. A good place to start if you don't want to pay Adobe any money.
Photoshop is the standard program for post processing, and you will find the most resources for this program. It also has many plugins available specifically for astrophotography. It is expensive but worth it depending on your goals. Lightroom could be used as well but I don't really like it.
Pixinsight is a great all in one tool for pre and post processing. If you were going to pay for one program for your astro needs, it should be this one. It has a host of options for detail and color enhancement, some of which will not be found in other post processing programs.
Finding a Time/Place to Shoot:
The night sky changes from week to week and month to month, to get the most out of your time you need to plan around weather, light pollution, and moon phases.
Unless your trying to take pictures of the moon, the moon will hurt your ability to capture images of space. You want to go out to image when there is a new moon, or when the moon is not visible or very bright while your target is out. I like to use the app PhotoPills to view the best moon phases, as well as the app SkySafari Pro to get a more detailed idea of where the moon and my targets will be in the sky.
This is going to be the most important condition which determines how good your images will be. The darker the skies the better the image. You can view a light pollution map here to help get a good idea of where dark skies are closest to you. Keep in mind not all dark skies are equal. On the North end of a city looking South toward the milky way, your conditions for imaging the milky way will be bad, because the light dome from the city will be high above the horizon. You should plan where you go to image on what you want to image. So for the milky way core you would want to look for a place to image with no nearby cities looking South. This may not be an option for you depending where you live, but if you have the options keep this in mind.
This is a comparison of unedited images both taken from 'dark sites' on a light pollution map, but demonstrates the effect of nearby cities. Top is from Bloody Basin, AZ and the bottom is from Green's Pool, Western Australia.
Weather is an unpredictable chaotic element, and will be difficult to plan around. My thought on weather prediction is to not rely on one single source for your weather forecast. I typically use a combination of cleardarksky and google searching weather conditions. If predictions are partially cloudy, I generally find its a 50/50 tossup on whether or not conditions will be good, so I may not bother on partially cloudy nights.
Choosing your Exposure Settings:
When using a DSLR for astrophotography, or any photography, there are three factors that will determine your exposure: exposure time, aperture, and ISO. Each will need to be tuned correctly to take a good astrophoto.
Exposure time is the most important factor which will drive your astrophotography. It is the reason why I strongly recommend you start out with a simple star tracker. Without a star tracker you will need to micromanage your exposure times so that your stars are not trailed too much, and you will have to deal with really intensive processing. If you want to see what dealing with that is like, you can see this video I linked earlier.
However there are times where shooting without a tracker makes sense, like if you are backpacking and need to save the weight. So if that is you, the exposure time you need to use is the longest exposure time where the stars do not trail too much. You can find this out by doing a bunch of math, OR you can do what I do and take a test exposure and see if it looks good. Just keep trying new exposure times until you find the acceptable limit.
If you are using a tracker, then you have some more options for exposure times. Your exposure wont be limited by the rotation of the earth, but it will be guided by the other two exposure settings, aperture and ISO.
Your objective with exposure time on a DSLR when tracking is to find the smallest exposure time which will properly expose an object. You do not want to leave a bunch of data clipped in the shadows or highlights. Ideally you want the hump of the histogram to be just pass the bottom end so you know that you aren't clipping data.
When I say 'clipping data' I'm referring to how a digital camera with a 16bit readout can only write pixel values between 0 and 65535, where 0 is black and 65535 is white. If the exposure is too short, much of the detail in the image will have a brightness value near 0, because there was not enough time to collect light on that pixel. If the exposure is too long, it will read 65535 in large portions of the image where a pixel is pure white and saturated because it collected too much light. Anywhere between 0 and 65535 is properly exposed.
The thing you need to keep in mind is that while you are exposing with your DSLR, your sensor is heating up, and the thermal noise, dark current noise, and amp glow will be building up while you expose. If you live somewhere that is hot in the summer like in the southwest USA, this will be a much more important factor than you will expect. In the winter it is less of a concern but your sensor will get HOT in the summer. This is why I recommend you expose properly, but as short as possible. Otherwise you are accumulating extra noise for no reason.
Aperture is a bit more simple to pick than exposure time. You simply need to pick the widest possible aperture which does not exhibit any optical problems like chromatic aberration or astigmatism, etc. In astrophotography you need as much light as you can get, so faster will always be better. If your lens is sharp and defect free wide open, then don't be afraid to shoot wide open. A lens like the Rokinon 135mm f/2 will give you amazing results wide open at f/2. This fast speed even allows me to shoot with 30 second exposures for deep sky.
For a TLDR, usually an ISO between 800-6400 will work. If you have the dynamic range go for the higher ISOs.
ISO is another setting which is a bit complicated, and first requires a quick word about how cameras work. A camera first collects light as photos, the photons are converted to electrons at the photosite (pixels), and the charge values at each pixel are converted to a digital signal (the 0 to 65535 number we discussed earlier). Before they are converted into a digital signal, we have an option to multiply the voltage values by some constant number or "gain" before they are read out and converted to a digital signal. This number that we multiply our signal with is the ISO of the camera.
If you remember our earlier discussion about not clipping the histogram above 65535, you can see where the ISO comes into play. If we increase the gain or ISO before readout, we lose dynamic range because dim signals which wouldn't have clipped with a gain of 1 may be too strong with the gain multiplied in, causing them to be read out as 65535 or pure white.
The upside to higher ISO is that noise performance is better, which may seem counterintuitive, but it is true for astrophotography. Our consideration is sacrificing dynamic range for noise performance with ISO choice. I will go more in depth about this later but this will suffice for beginners.
This figure illustrates how ISO pushes the upper end of signal out of the camera dynamic range, but also allows for the lower end values to be quantized or represented by more pixels in the camera dynamic range, improving noise performance.
Every camera is different, and some are even ISO invariant where the gain is a digital gain applied after readout. Your best bet is to check what ISOs other people are using for the camera model you have and go with that. For my Canon 6D, I shoot at ISO6400 for astro, but anywhere between 800 and 6400 will be a good starting point typically.