Ahh, the night sky. The long bright dark of magical orbs so close, yet so far away. In recent years, the rise of camera and lens technology has made capturing images of the night sky increasingly achievable. We are beyond lucky in New Zealand to have low levels of light pollution, making stargazing and astrophotography an attractive activity. A rather big thanks to folk like Mark Gee who have shown the world what is possible if we protect our night skies. It is quite ridiculous that you can drive 10 minutes from the capital city to do some top-notch stargazing. You can stare in awe at the Milky Way on a clear night. Yet, billions of people will never see more than a few stars, let alone our galaxy.
It’s nearly six years since I took my first (and rather average!) image of the night sky. With a bit of perseverance and patience, progression still continues to this day. I’ve written this as a guide for taking wide-field astrophotography images using a DSLR or mirrorless camera. By wide-field astrophotography, I’m talking about an image that contains the night sky and some kind of landscape.
What do I need
- A DSLR or mirrorless camera with a good sensor
- Lenses (anything with a focal length from 14-50mm on a full-frame DSLR)
- Batteries (plural)
- A solid and sturdy tripod (cheap and light increases risk of broken lens/camera, look at your tripod purchase as insurance)
- Remote shutter (not a must-have, but it certainly helps)
- Head torch
- Warm clothes
- Clear skies away from light pollution sources
- A bit of luck with the weather
- Patience!
What camera and lens should I use?
This can be quite intimidating and confusing, with so many options available. Sensor size is the important thing here; the bigger the sensor, the more light you can capture. I use a Canon 6D MkI and MkII for my nightscapes. These models are full-frame cameras, which means their sensor size is the same size as those in the old 35mm film cameras. When it comes to sensor sizes, it generally falls into three sensor sizes (from biggest to smallest):
- Full frame;
- APS-C (on DSLRs and mirrorless); and
- Micro 4/3 (mirrorless)
If you’re not sure what sensor your camera has, just search online “your camera model name + sensor type” to find out.
Where should I go?
A nice dark place, away from city and streetlights. Take a friend. It’s good to have company and if one of you trips in the dark, you can help them out/drag them away from a nearby seal/laugh at them. Maybe all three? Take your pick.
The Milky Way rising above the Wainuiomata coastline, 2016, photographed with a 14mm lens
When is the best time for taking photos of the night sky?
In the southern hemisphere, February through to November offers plenty of opportunities to capture night sky images. Have a look online when sunset and sunrise occur. After the sun sets behind the horizon, we go through civil twilight, nautical twilight, then astronomical twilight and THEN it is night-time, where the stars really join the party. The below diagram gives you a good idea of the different lights after sunset;
Diagram showing the stages of light either side of sunset. We want to be taking our nightscapes from astronomical twilight onwards. Source: PhotoPills
It is also advantageous to shoot a few days either side of the new moon. Have a quick search online to see when this will be. The moon puts out a considerable amount of light, and less ambient/natural light helps the stars and the Milky Way pop a bit more. Every little bit helps when trying to capture more stars! A bit of moonlight can light up the foreground nicely, but at the cost of capturing fewer stars. From experience, you have a window three to four days either side of a new moon tends to provide for ideal astrophotography conditions.
Framing the image
There are two approaches to this. The wiser option is to plan ahead, do some scouting and, during the day, go to the area you would like to do some astrophotography. It helps you spot hazards and limitations to your shoots, which might become even more problematic at night-time. The other approach is to just get away from the light pollution and, in the dark, figure out what makes a nice photo. If you do choose this option, which I’ve done plenty of times, do have a look on Google Earth beforehand, to give yourself some idea of what kind of landscape and scenarios you’re getting yourself into. Navigation and such can be difficult after dark. I’ve nearly stood on a seal before and got lost on a glacial moraine for 15 worrying minutes. And that was with a day-scout! Do be careful.
I use an app called PhotoPills for planning my astro shoots, and I hear good things about Star Walk, too. PhotoPills lets me know where the Milky Way will be and when, so I don’t have to play guessing games where it will be. Roughly speaking, you’ll see the core of the Milky Way (the big bright part) rise ~SE in Feb-April, East in May-June, and always heading toward the western horizon through until November.
Milky Way setting along the western horizon, Cape Palliser, 2016, photographed with a 14mm lens
A useful guide when it comes to taking your photo; it should still be a good photo without the stars in it. You want to strike a nice balance between the stars and the surrounding landscape. Find points of interest for your foreground, perhaps the ocean, a mountain range or some trees? Make sure you’ve got that horizon straight, as this gives you more room to play with and more cropping options when it comes to post-processing. The rule of thirds also applies to astrophotography, which you can read more about in one of my earlier blog posts.
Focus!
This is one of the most important steps. It’s just a little frustrating having gone out into the cold for hours on end, taking photos of the night sky, getting excited the same way we do when Dr Ashley Bloomfield says “Tena koutou katoa”, then coming home to edit and realise nothing was in focus. That’d make you a bit annoyed, I think. So, what you want to do is switch your lens to manual focus (marked MF), and move the focus ring on your lens to the infinity mark.
Move the focus ring so the bottom white line aligns with the infinity mark (the vertical line associated with the infinity symbol, which looks like a sideways 8)
What settings should I use?
It depends. These are two words I keep coming back to with most things to do with photography. It really depends on what you are trying to achieve, what you’re trying to capture, what light conditions are like and what kind of gear you are using.
- Shutter speed
The shutter speed is how long the shutter is open when taking a photo. Usually photos are taken with a shutter speed of a fraction of a second. For Milky Way photos, you will be taking a long exposure. The longer the shutter is open, the more time we allow for the camera sensor to capture light. We can take exposures up to 30 seconds long in order to get the best images of the Milky Way. If we have the shutter open for too long, though, the stars will start to trail. This can look pretty neat, but for the purpose of this tutorial, we want to capture a nightscape image without trails.
Due to something called crop factor, the effective focal lengths of your lens can be a bit different from the focal length of your lens. This all depends on your camera sensor size. Again, we are comparing to the old 35mm film cameras. The table below gives you an idea of how focal lengths are affected by sensor sizes;
I’ll come back to this table in a second. So, how long should you keep the shutter open? The 500 rule is a useful, but not gospel, guide here. This gives you the time (in seconds) before your stars will start to trail in your image. The formula is:
500/(lens focal length x crop factor) = ideal exposure time (seconds)
So, if I’m using a 24mm lens on a full-frame camera, it would be 500/(24mm x 1.0) = 20.8 seconds. I’d just rock a 20 second exposure at this focal length. It is fine to use shorter exposures as well, say 10-15 seconds using a 24mm lens. If you are really unsure and maths ain’t your jam, a 15 or 20 second exposure should be ok.
- Aperture
This is about letting in as much light as possible through the lens and is measured by something called f-stop. The lower the number, the wider the aperture and the more light the lens lets in to your camera. Normally, the depth of field aspect of aperture should be considered, but we’re taking photos of balls of gas burning billions and billions of miles away. So, depth of field becomes a bit irrelevant. Depending on what other settings you are using, an f/stop rage of 1.8 to 4.0 should let in enough light. Play around with your lens, some have certain sweet spots for image quality. I tend to use a range between f/2.0 through to 3.5, with f/2.8 the most common.
- ISO
ISO is about how sensitive to light the sensor in your camera is, and typically ranges from ISO100 - 25,000 on most modern cameras. The higher the ISO, the more light-sensitive your sensor becomes. During the day, we tend to use an ISO setting of 100 through to 800, depending on the conditions. For astrophotography, you really need to be shooting at ISO 1600 (bare minimum) through to 10,000. For Milky Way images, we want to increase the sensitivity of our sensor, because it is really dark and light is scarce. The trade-off in increasing your ISO is that your image becomes a bit noisier. What I mean by that is that your image becomes grainy. No worries, you can edit that in post-processing. Settings between ISO 3200 and 6400 works pretty well for my camera and lens combinations. Have a play around to see what works best for you.
The white balance
The white balance is a measure of temperature (measured in Kelvin) and, in a basic sense, is what gives a “cool” or “warm” vibe to your photos. The lower the number, the “cooler” the image. Changing the white balance is handy for a number of reasons, mainly because it gives you some consistency and (relative) realism to your images you have captured, which is useful when you go to edit. Change the setting on the back of the camera (odds are it will be set to AWB, for auto white balance) and select tungsten (3200k) or white fluorescent light (4000k). Either is fine, you can tweak this as necessary in post.
The galactic core of the Milky Way, 2019, photographed with a 35mm lens
Shoot in RAW
You have two options when it comes to the file format your camera records off the sensor; JPEG or RAW. Smaller file size is the big advantage when shooting JPEG. But that’s about it. RAW files are information-rich as they capture significant more detail, so the file size will be larger. This allows you to do a bit more to the image during the editing process without overcooking your photo. Think of it like a steak; the JPEG image is a minute steak, which will be ruined or overcooked easily during the editing process. On the other hand, RAW is a thicker cut, like a rump or sirloin. You can do a lot more to it before it leaves a bad taste in the mouth.
Ready to rock and (or) roll
Ok, now you’re all set to actually take a photo of the night sky. If you have a remote shutter, things are a bit easier. If you don’t, that’s fine, but you’ll have to change the drive mode in your camera so there is a delay from when you push the shutter to when the exposure starts. If you don’t, there is too high a risk that your camera and tripod are moving from when you’ve pressed down on that shutter.
The Magellanic clouds and the tail of the Milky Way, Castlpoint, 2015, photographed with a 14mm lens
Things to avoid
- Crooked horizons!
- A lot of people tend to use a torch or light source to dazzle the foreground or an object of interest in the frame. It’s incredibly difficult to achieve a natural look that complements the image, and doesn’t distract you from the wondrous night sky. Plus, you get a load of weird colours in it, and that can be a massive pain to edit
- You see many images online that are actually multiple exposures (one for the foreground, one for the night sky) put together in Photoshop. And more often than not, you wouldn’t know about it. Although it can look neat, I do think it is quite misleading. It isn’t necessarily realistic and muddies the waters between what’s real and achievable. You start getting into the realm of digital imagery, opposed to out and out photography. But that’s a chat for another time!
Next: how to edit
That’s part one done. Coming soon, how to edit the beautiful frame you just captured. Every night sky image you see has been edited in some way. In fact, the camera even does some minor editing for you! The next post we’ll go through how to edit and ensure you end up with a natural looking (entirely subjective) image with a bit of “pop”. Speaking of which, you can now head out and pop off a few dark sky images of your own. Do try it!