How to Photograph Stars

June 13, 2012 // Around the World 2012, Featured, Photography

Some time ago, whilst in Britain’s Lake District,  I saw the most incredible stars in the sky, with clouds of stars clearly visible. At the time, I wasn’t up to speed with my photography, so all I have is a magical memory of that night.

I determined to be better prepared for my travels around the world, especially because I was going to pass through two of the best places in the world to look at the night sky: the Outback in Australia, and the Cook Islands: remote and alone in the vast emptiness of the South Pacific.

I had packed a Nikon D5000 12-Megapixel Digital DSLR. I also packed a couple of kilos of camera equipment, including different lenses, filters, batteries, a remote trigger, SD cards and the like. However, all you need is a tripod and a SLR to get some pretty awesome shots, like this one I took in the Outback:

Star Trails – The Outback, Australia - 16 minute exposure, f3.6 at ISO200

The Basics

The important point about the SLR is that you can control three variables when you take a photo. Understanding these variables is essential if you’re to capture the faint light from the stars:

  1. Shutter Speed - This determines how long the sensor/ film will be exposed to light. It is measured in seconds.
  2. Aperture - This determines the size of the hole through which light enters the camera, and therefore how much light will hit the sensor/film whilst the shutter is open. It is measured in f-Stops (lower is a bigger aperture)
  3. ISO Sensitivity - This is the setting that determines how rapidly the sensor reacts to light hitting it. Higher is more sensitive. If you’re using film, you can buy more sensitive film.

Our eyes are sensitive to the light of the stars and we compensate for their dim light in ways that a camera can’t, unless you leave the shutter open for a long time and possibly fiddle with the sensitivity.

Controlling Shake

At the very least, you’re going to have your shutter open for twenty seconds. You cannot possibly hold perfectly still for even one second, let alone twenty, so it’s essential that you use a tripod.

Your results will be massively affected by any shakes or bumps. I remember trying to take a low-light shot of some samurai armour in Himeji Castle. Unfortunately, I was working on a thin wooden platform which other tourists were walking over and this caused a lot of shake. I was not satisfied with the sharpness of the photos.

It’s worth also using a remote trigger to fire the camera. This will allow you to push a button that isn’t physically connected to the camera, which will reduce shake further. At the very least, set the camera to a timer delay so that you can push the button and step back before the camera shoots. Using the timer delay trick rules out taking long very long exposure shots without shake. I’ll explain why later…

One final trick I discovered later in my travels is that some cameras feature a setting called, “Exposure Delay Mode”. When you take a photo with an SLR, a small mirror inside the camera flips up as the shutter opens. This can cause a tiny amount of shake. You can set the camera so that the camera waits about a second between flipping the mirror and opening the shutter.

Photographing Star Trails

The Earth rotates. It rotates at around 1700 kilometres per hour. This means that the stars appear to be rotating around the Earth, but in actual fact, the your perspective as an observer on the earth is changing at a staggering speed. The only reason we don’t notice this is because the distances involved are too vast for our tiny brains to perceive. Point a camera at the stars for twenty minutes, and you can capture almost 600 kilometres of rotation on camera.

Stars over Aitutaki – 18 minute exposure, f3.6 at ISO200

With the combination of a rock-steady tripod and plenty of time, you can get some pretty cool effects with stars. I took the photo above on a beach in Aitutaki in near pitch darkness with only starlight lighting up the sky. To take photos with star trails, try this:

Step One – Working out your exposure time

Calculating your exposure time can be tricky, so if you’re using digital, just try the trial and error approach. Depending on what I get from this approach, I usually err on the side of caution and add on half again. You can always correct an overexposure more easily than an underexposure:

  1. Set your camera on the tripod.
  2. Point your camera at the subject
  3. Put your camera in Manual Mode
  4. Set your ISO to be something high, like 1600.
  5. Set your aperture to be as wide (Low f-Stop) as possible.
  6. Set your shutter speed to be 30 seconds
  7. Try to focus on something in the foreground (very difficult in the dark).
    • Alternatively set your lens to manual focus and turn the focus to infinity ?
  8. Take the photo!
  9. If the photo looks good, then you’re in business! Multiply 30 seconds by 16 (if you were at 1600 ISO) to get the exposure time at 200 ISO – 8 minutes in this case.
  10. If  the photo doesn’t look good, try again for 30 seconds at a higher ISO to work out how much you’ll need to multiply your 30 seconds by.
  11. For example – you might have tried again at 2400 ISO, in which case multiply 30 seconds by 24 to get a 12 minute exposure time at 200 ISO

Step Two – Taking the Photo

  1. Set your ISO to 200.
  2. Keep your aperture wide.
  3. If you have it, turn on “Exposure Delay Mode”
  4. Dial your shutter speed to the “BULB” setting. Some cameras refer to this as “TIME” or similar.
  5. Set the camera to shoot from the remote trigger.
  6. Press the remote trigger button to open the shutter. Because you’re on “BULB” mode, the shutter will remain open until you press the button again.
  7. Note the time – you can now wander about or ponder the vastness of deep space for the duration of the exposure, or until your brain leaks out of your ears, whichever is sooner.
  8. Once the time is up, go back to the camera and close the shutter by hitting the remote trigger again.

You cannot use the timer delay trick as effectively here because you have to return to the camera and touch the camera body to close the shutter. This can introduce shake into your picture.

Some of your exposure times may be as long as 20 minutes. I have seen some photos that took an hour. Take as many photos as you can stand to take without boredom setting in – you’ll really appreciate the effort when you get home and review your photos.

Photographing Stars without Trails

Star Trails look pretty cool. The only aesthetic downside in my opinion is that you have to explain what the trails are, and the photograph doesn’t really capture what you saw at the time. Star trails are caused by the rotation of the earth being noticeable with long exposure times, so the answer is to have a faster exposure (anything at 25 seconds or below will be fast enough to make the movement of the stars unnoticeable).

Stars over Rarotonga – 25 second exposure, f3.6 at ISO3200

Follow the instructions above, but this time, set your ISO setting as high as it will go to capture as much light in 25 seconds as possible. High ISO settings can result in noticeable “noise” (graininess) in your picture, even in newer cameras. It’s therefore worth playing around with the ISO settings and seeing just how low an ISO setting you can get away with whilst capturing a great picture.

Messing About With “Light Painting”

I was so bowled over with the stars on Rarotonga, that I knew I had to get in the photo with them! The problem was that I would look like a silhouette against the night sky if I even registered on the camera at all.

Me with the stars of Rarotonga – 25 second exposure, f3.6 at ISO3200

You can solve this problem with a torch and a technique called “Light Painting“. I spent an evening with Jose on the beach shooting the stars and we would take turns to run in front of the camera, and strike a pose for a couple of seconds. Meanwhile the other person would shine a torch on the subject, painting him with light for a count of two, before turning off the torch. The result was this wonderful, eerie effect. We thought it looked as though we were about to be beamed up by alien abductors!

 

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