Braving the bitter cold of winter nights in the Kgalagadi, Wild’s editor got spaced out on starry skies. By Romi Boom
My recent trip to the Kgalagadi Transfrontier Park coincided with dark night skies. The waxing crescent moon in June provided the perfect opportunity for a few nights of astrophotography, and I was keen to experiment with star trails.
To capture stars over a long exposure so that they leave behind a ‘trail’ or light stream is magical and captivating. What you actually record are stationary stars and the rotation of the earth on its axis – something we cannot see with our own eyes. It reminds us that our planet is spinning out in space.
In the southern hemisphere you must aim the camera to the south celestial pole so that all the stars will circle around it like streaks. Aiming the camera towards the east or west creates straight-line streaks.
The technique is quite simple. Head for wilderness places with clear skies – Kgalagadi’s Wilderness Camps are absolutely perfect, so too Cederberg and any number of Wild Card parks and reserves. Any ambient light or clouds will make the stars less visible. For the photograph to have a sense of place, you will need a stationary object in the foreground.
Before you head out into the night, make sure your camera is capable of shooting in ‘bulb’ mode, and bring a tripod to stabilise your camera during the long exposures. A cable or remote release is extremely handy but not essential (more about that later). Make sure the battery is fully charged since the cold night may cause battery life to be shorter than usual.
Arriving mid-afternoon at Bitterpan Wilderness Camp, I soon met up with two other keen photographers who had come there with the exact same intention. Amazingly we all had the identical camera (Canon 7D) and Manfrotto tripods. In no time we were best mates. Although all of us had different lenses, everyone opted for the widest angle (15–18mm) for this specific scene.
Once you have set the correct focus, you have to turn your auto-focus off otherwise the camera will attempt to re-focus at night. Image stabilisation should also be off whenever your camera is on a tripod.
I was aiming for a 30-minute exposure with a wide aperture of F4 to ensure the greatest possible amount of light entering the camera. With a smaller aperture, the star trails will be very dim. I set the ISO at 100.
For exposures longer than 30 seconds, you need to set the camera to the ‘bulb’ setting. The bulb setting holds the shutter open as long as you hold down the shutter release. There is no way you can do this with your finger and not move during a long exposure. You will need a remote release – or you can simply press down the shutter and secure it in place with duct tape, winding it around the bottom of the body. This is exactly what we did and it worked perfectly, first time.
To make your shot unique, you can use a flash or spotlight to highlight a foreground element, like a structure or tree. Too much light will distract from that beautiful star filled sky you are about to create.
More techno stuff
An alternative to doing it all in one shot is to shoot multiple shots and ‘stack’ them afterwards using computer software. With a cable release you can set your camera to continuous shooting and lock the cable release and your camera will continue to make images until you unlock it. Many photographers find that shooting multiple images and stacking them yields much nicer images than those done all in one shot, but being impatient, I wanted to see immediate results. With a single shot, the biggest concern is noise.
One night I decided to do it the conventional way with the remote release instead of duct tape. My Canon 7D spent a lot of time in ‘busy’ mode right after the long exposure. When this ran into more than 10 minutes (I later learnt that it usually takes more time than the actual exposure), I became exasperated and simply removed the battery. Back home I got a satisfactory explanation for the long recovery time I was experiencing.
Any long exposure will take time to process in the camera. A long exposure means very low light and thus usually more noise. The camera has to apply noise reduction (the function is usually set in the CF menu) and then process and save the image. By default NR kicks in for any exposure over 1 second. The built-in software is rather aggressive: it induces the camera to make a second ‘blank’ exposure with the shutter closed and compares that to the image you took. It then uses the noise pattern created to filter noise from the first (the actual) long exposure. This is normal! It even happens if you are shooting in RAW, because noise reduction is applied to the files that are processed by Canon’s DPP software that came with the camera. The alternative is simply to switch NR off.