Getting Started in Astrophotography
It’s no secret that getting started in astrophotography can seem prohibitively expensive. We’ve all seen the images online of people using their own observatories at home, with thousands of pounds worth of equipment inside.
However, in this tutorial I am going to show you that money doesn’t need to be a blocker if you’re just getting started. You can start with whatever gear you have, and yes that includes smartphones!
So what gear do you actually need to get started? Well, you’ll definitely need a camera! I use a Canon DSLR but there’s no need to go and buy a new one, whatever camera you have will suffice for now.
Ideally, you’ll want to have a tripod, but honestly, if you don’t already have one you can get creative by using a table and a stack of books to point your camera at an angle towards the sky, or even the edge of a window frame!
That’s it! You don’t need anything else to get started. If I’ve learned one thing in astrophotography, it’s that it’s simply not enough to point your camera at the sky and take a picture.
You’re going to need a basic understand of how photography works, and that means taking your camera out of “Auto” mode and changing some settings ourselves. Let me break it down for you.
It’s important to understand that in astrophotography, we’re trying to achieve the best possible signal to noise ratio that we can. There are some settings that we can change to help us achieve that.
Aperture refers to how open your lens is, which is expressed in f ratios. The lower the number, the more open your lens is. The more open your lens is, the more light that your sensor is going to collect – this is key to astrophotography.
If you’re using a kit lens, the lowest setting is probably f3.5 – this is fine. If you have a more premium lens such as an f2.8, even better.
ISO will affect the exposure of your image. A higher ISO will produce a brighter image. However, the higher you go, the more noise you will add. In astrophotography, we’ll generally be using ISO800 or ISO1600 on a DSLR but this is camera dependent and does vary. ISO is very important for capturing those faint details.
This is the amount of time the camera will be capturing light. Seeing as we’re going to be imaging at night, we want to be capturing light for as long as possible. This will vary depending on your focal length and whether you have a tracking mount or not.
As we’re keeping this simple, let’s assume you don’t have a tracking mount. The amount of time we will therefore be able to expose will depend on focal length, which will determine how long we can expose before we get star trails.
As the Earth is rotating and our camera is stationary, at some point during a long exposure, we’re going to start seeing star trails, which can make for a very nice image, but that’s a whole different lesson.
The trick here is to find the sweet spot between a long exposure and no star trails. There is a rule of thumb called the 500 rule. While it isn’t the most accurate, it can be a good indicator for a place to start. We’re essentially dividing 500 by the focal length of our camera lens.
For example, if we’re using a 50mm lens then 500/50 is 10. We can therefore expose for 10 seconds. The reason I this isn’t fully accurate is because that is assuming a full frame camera, when most people will be using a crop sensor, which is 1.6x the focal length, so a 50mm lens is actually a field of view of a 80mm lens, and so 500/80 means we can actually only expose for 6.25 seconds before star trails.
Again, in practice this may not be right and it’s best to use the screen on the back of the camera to zoom in and check for egg shaped stars. Egg shaped stars means you’ve exposed for too long.
Taking Test Shots
Now that we know the settings we’re going to use, it’s time to take a few test shots. The only variables you’ll want to change here are shutter speed for star trails and ISO to avoid too much noise. Unless you’re in a light polluted area then you may also find that you need to adjust the aperture too.
Take some test shots with various settings and find that sweet spot. Now that we have that sweet spot we can finally start taking some images! In astrophotography, a neat way to improve the signal to noise ratio is to stack your images on top of each other.
So what we want to do is take as many images as possible. To reduce the noise further, we can also take calibration frames, which I won’t talk about here as I have another video, which I’ll link down below, where I explain what calibration frames are and how to take them.
Other Factors to Consider
- Battery charge – make sure your batteries are fully charged and that you have spares. Alternatively, if using a DSLR, why not try a dummy battery? Ensure you buy the right dummy battery for your model.
- Light pollution – Use this map to determine your local light pollution. Or download the Clear Outside app, which not only determines your sky quality, but also keeps an eye on those pesky clouds! Light pollution filters are also very effective in killing light pollution, but with short exposure times they shouldn’t be necessary until you’re using a star tracker.
Stacking your Images
Now that we have our images, and maybe some calibration frames too, we’re going to need to stack them. To do that, we need some software. I use DeepSkyStacker, and I have a full walkthrough tutorial of how to use to save going into the full detail here.
Basically this is going to align all our images and stack them on top of each other to improve our signal to noise ratio.
Once we’ve stacked our images, we can make improvements to them by using post-processing software. I use Adobe Photoshop, but if you’re looking for free software then GIMP is a good place to start.
Here we’re going to start stretching our data to tease out those finer details and give our image a better look. If you’re sat there thinking that’s cheating, then I can tell you that every astrophotography image you’ve ever seen will have had these techniques applied to them.
It’s absolutely necessary to bring out the faint details, whether that be the Milky Way or a deep sky object. Remember, we’re not adding artificial data here, the data is there in the image. Those photons have hit our camera sensor, all we’re doing is pulling them out.
There are lots of Photoshop tutorials on YouTube to check out!
Once you’ve mastered everything we’ve talked about in this video, you may feel like you want to improve your imaging by buying a Star Tracker so that you can take longer exposures. Be sure to look out for part 2, where I will explain what a star tracker is and why we use them.