An introduction to astrophotography with award-winning photographer Mark Gee
I remember the first time I went out to shoot the night sky. I knew that I had to shoot a long exposure to capture the stars, but that was about it. I learned a few things that night and I’ve continued learning ever since.
Astrophotography has been a passion of mine for more than six years. I was hooked after seeing images from the Royal Observatory’s first Astronomy Photographer of the Year in 2009. Since then, astrophotography has taken me all over the world and I have spent many hours under the night sky attempting to perfect the craft. By 2013, I’d come far enough to win the overall prize in that very same competition as well as winning the Earth and Space category.
Getting to this point wasn’t easy and I’ve learned a lot through trial and error. My hope is to make it a little easier for those just starting out by sharing some simple tips. While there are several types of astrophotography, I’ll concentrate on how to shoot landscapes under the night sky, known as wide-field astrophotography.
To begin with, let’s talk about cameras and lenses. Ideally you want a DSLR camera with a full-frame 35mm sensor. Good examples of these are the Canon 6D, Nikon D600 or the Sony a7S. While you can get away with using crop sensors and inferior models, full-frames will offer the best results.
As far as lenses are concerned, you will need what they call a good, fast lens, or a lens where the maximum aperture is at least f/2.8 (or an even lower number, if it doesn’t break the bank). Buying a lens without an autofocus feature will save you money too, as autofocus is basically useless in night photography.
A great value lens for astrophotography is the Rokinon 14mm f/2.8. I know a lot of astrophotographers using this lens because it’s optically sharp, helping you capture crisp night sky images.
One of the first things I learned while night shooting was the importance of a sturdy tripod. The first time I gave it a try happened to be an extremely windy night and I had my camera mounted only on a light aluminum tripod. The strong gusts nearly blew it over several times, but adding a few rocks to my camera bag and hanging it below the tripod saved the day (or night, to be exact). Using a heavier, stronger tripod also helps to minimize camera shake, which is an important bonus. To add stability, you can always hang a bag or weights from the tripod like I did.
Having sorted out the tripod, I got down to shooting. The image I got back looked OK, but I noticed that due to the earth’s rotation and my long exposure, the stars were streaked, giving me star trails. For some, this may be the desired effect, but not me. With some digging, I managed to find a formula on the Internet called the “500” rule. It’s a straightforward calculation in which you divide 500 by the focal length of your lens. The answer is then the maximum exposure time with which to shoot in order to avoid star trails.
Here’s an example: I was shooting with a 14mm lens on a camera with a 35mm full-framed sensor. To work out my maximum exposure time, I would divide 500 by 14, which equals 35.7. Thus when using my 14mm lens on that camera, it’s safe to shoot up to 35 seconds without too much noticeable star trailing. If you’re using a crop sensor camera, then you can use this formula: 500/(focal length x crop factor) = maximum exposure time.
To Shoot, You Must Plan
When choosing locations for my photographs, I look for remote locations where I know there is going to be very little light pollution and —hopefully—something interesting in the landscape to shoot. But before going out, it’s essential to do some advance planning.
I didn’t always do this and I learned my lesson quickly after driving almost 2 hours one night to a location I had never been to before. When I arrived I found a locked gate across the road preventing me from reaching the spot for my shoot. Since then, I do a lot more research on accessibility, and check out my locations during the day to plan the shots I want.
Focus Your Efforts
One of the trickiest things to do in night photography is to perfect your focus. I’ve learned the hard way that even when images look fine on the camera display, it’s important to enlarge them to check more closely. I failed to do this on some early outings, only to get home and see that in every shot the stars were out of focus. My “amazing” shots turned out to be a lot less so after all.
To keep your focus sharp there are a few methods, but the one I like best is using live view mode on the back of the camera. Because you are shooting in a dark location, autofocus doesn’t work, and you can’t always rely on the infinity marker on your lens (some lenses don’t even have them). So, first turn off autofocus. Then turn your live view on and point your camera at the brightest star (or distant light source) you can find in the sky. You should be able to see that on your screen. Once you locate this star you can zoom in on it as much as possible and manually rotate the focus ring on your lens until that star is sharp.
Settings and More Settings
One of the main questions I get when I post my images to social media is “What settings did you use?” Although just getting the settings right isn’t going to yield an award winning image—scene composition, for example, is central too—let’s delve in to get you started.
Because we are shooting mostly in complete darkness, we need to allow as much light through the lens and onto the sensor as possible. This means shooting in manual mode as the camera won’t be able to work out those settings automatically, using a long shutter time (as worked out with the 500 rule), and opening the aperture as wide as possible. We also need to amplify the sensitivity of the sensor. This is done through our ISO setting. Just be sure not to raise the ISO too high because that will introduce a lot of noise into your image. You will need to test how your camera handles different ISO settings. As with everything else, give it a try.
You will probably have to experiment with your settings depending on what camera and lens you will be using. I shoot with a Canon 6D and a Canon 14mm f/2.8 lens, so in a dark environment with little or no light pollution on a moonless night, my settings are a 30- second shutter speed, f/2.8 aperture and an ISO of 3200. If I am shooting in a more light-polluted environment or when the moon is in the sky, then I would take my shutter speed to around 15 seconds and leave the other settings as is.
The value when you shoot that will probably differ most from mine is the ISO. Unless you are using a camera that can handle relatively high ISO values without too much image degradation, will likely have to lower it. But whatever you do, don’t use your in-camera noise reduction function, as you are better off controlling image noise reduction through your image-processing software once you take a look on a big screen.
Astrophotography can be frustrating at times, but it’s a rewarding experience once you score your first great image. Hopefully these few tips will help along the way.