Imaging the ISS
Over the last while, I’ve had many requests via Twitter to write a ‘How To’ on imaging the International Space Station [ISS]. So I’ve decided to get the finger out & put a few lines down.
Where to start……
First things first, the most important thing to do is to plan well. Forward planning is vital to any night sky shot, along with a steady tripod and a warm coat. There are quite a few websites and twitter feeds that can help you with your planning. Even though it only takes about an hour and a half for the ISS to complete an orbit of the planet, you could be waiting quite some time under the night skies before the station appears above. The station only appears for a short time [about 1-2 weeks] & then re-appears again many weeks later. This is due to the orbit of the station above earth.
One of the best sites on the web for ISS positioning & flyover times is a site run by Chris Peat called http://www.heavens-above.com – simply register & key in your location & you can get a listing of the next 10 days ISS flyover times. Each flyover is split into three sections – the start, the highest point & end of the pass. Each pass is also give a brightness value. The brightness [mag] is a confusing number at first. The important thing to remember is the lower the number, the brighter the station will be in the sky. This is the same value that’s given by astronomers to other stars & planets in the sky. So -3.3 is very bright, while -0.4 is not as bright. Each section has an exact time, height in the sky & what part in the sky.
So for example the flypass of 16th April [above]starts at 22:31.07 in the West at a height of 10 degrees. At it’s highest point in the sky, the station will be 60 degrees in the South at 22:34.19. The station will disappear at 22:34.57 in the South East at 47 degrees. 0 degrees is the horizon & 90 degrees is straight above.
Another worthwhile link is twitter based - https://twitter.com/#!/twisst who, when you register, will tweet you each day the ISS is due to pass your location & provide a link in the tweet to useful information about the pass.
I would also highly recommend you follow Adrian West, aka virtualastro on twitter – his address is https://twitter.com/#!/virtualastro You’ll get load of interesting links from Adrian on the ISS and all things that you can see in the sky. His website is http://meteorwatch.org
Keep in mind the ISS will appear above in the evenings for a short while – about 1-2 weeks, then will not be visible as the passes are only during daylight hours. Next time it will appear during the early mornings [I’m not good at early mornings, so I tend to skip those ones], ‘till it appears back again during the evening times. The ISS is never seen late at night over northern Europe as the light of the sun is needed to reflect off the station in order for it to be seen.
So now you have all the details you need for knowing when you’ll get to see the ISS. Next thing is to plan when to take your shots. Two very important points are check your weather forecast & move away from the city / town lights. You need clear nights to get the really good shots of the station, but you could be lucky is there were only a few whispy clouds in the sky. These can add a little something to your shot, once they don’t block the path of the station. Being far away from built up areas is important as light pollution will ruin what could have been the perfect shot. To get the streak of the station across your image, you’ll need to have your camera’s shutter open for 45 to 70 seconds and any light from nearby street lights or passing cars will ruin a great image. I’ve taken long exposure shots of a minute or more of the sky in a dark garden, but the lights of Dublin, over 30 miles away, caused the sky to glow a bright orange. I’m very lucky to live in the countryside, so I tend not to have to travel so much to get my shots, but living in a town or city and taking your shot from the front or back of your house will almost certainly give an orange hue to your sky. Feel free to take a few tester shots in your back garden, but trust me, you’ll want to find those darker places for future images.
Next on the list is equipment. I would recommend you using a DSLR camera, so you can manually change your camera settings, but a half decent point and shoot will work. Very important is fully charged camera batteries, a steady tripod, a torch, a mobile phone and a compass. If you have a shutter release cable, that would help if you plan to shoot more than 30 second exposures. Also important is a warm coat & even a flask with a hot drink – just in case. Clear skies usually mean very cold nights. It’s one of the drawbacks of shooting the night sky. Do bring along a speedlight / flashgun if you’d like to try to light up part of your shot.
Once you’ve picked your location to shoot the station, set up your tripod & use your compass to have your camera facing south. In northern Europe, the ISS will always travel in the southern sky heading from the west to the east. All the details from heavens-above.com as mentioned earlier will inform you when to look for the station in the sky, so you can have your lens pointing in roughly the right area of the sky. I always try to get to the location in plenty of time to allow for a test exposure or two before the station appears, in case I’ve to make a few settings adjustments beforehand.
For your camera settings, I generally start off in bulb mode. This will only work if you have a shutter release cable which will hold the shutter open without having to touch the camera & lead to camera shake. In bulb mode set your ISO to about 800 with an aperture of f2.8. If you have a smaller aperture lens, say f4.5-5.6, I’d suggest increasing the ISO to 1000+. This is where the test shots are very important. There’s nothing worse than setting your camera, taking the shot & then finding out you’re way too dark & underexposed. One other thing to take into account is that shooting at night means your camera’s autofocus will not work at all. The best way to avoid your camera hunting for something to focus on & missing the shot is to switch your lens to manual focus. Once this is done, set your focus ring to infinity & then bring it back a slight bit. Now you’re all focused & ready.
If you don’t have a shutter release cable, the work around would be to switch your camera to shutter priority mode and take a maximum 30 second shot, but do use a 2 second delay for your shot so as not to shake the camera. Keep your ISO to 800 – 1000 with as wide an aperture as you have as above.
I’d recommend using the widest angle lens you have, so you can take in as much of the sky as possible. I use my Canon 16-35mm f2.8L lens, but before that I used the 17-40 F4L. Obviously, the wider the aperture of your lens, the lower you can afford to drop your ISO & this will reduce the amount of noise / grain in your image.
I’ve also learned to try to have some foreground interest in the shot. Try placing a group of trees, an old abandoned cottage or an old castle / monastery in the bottom of your shot to give a sense of scale to your image. I’ve found that a shot of a streak in the sky surrounded only by stars is not as pleasing to the eye. I’ve also tried lighting up the foreground with a flashgun / speedlight. I usually fire off 3-4 bursts of the speedlight at the foreground making sure that the speedlight itself doesn’t get into the shot. If the foreground is nearby, the firing the flash behind the camera will work. In situations where the foreground is quite a distance away, I have run in front of the camera in a dark jacket firing the speedlight at the castle etc ensuring that I am always between the lens & the firing speedlight so the camera will not pick up any of the flash bursts in the image.
So hopefully now you’ve taken your ISS shot & it’s worked out really well. You will need to process the image on your PC / Mac when you get home to either brighten or darken the image & probably remove some of the grain / noise that will appear from shooting long exposures with ISO levels of 800-1000. There are many fine image editing programs such as Lightroom, Photoshop, but one very decent free web application that is worth a try is http://pixlr.com
I am very interested in seeing your ISS images & would love if you could send me links to your images via twitter. You can find me on https://twitter.com/#!/shane_murphy
My images of the ISS can be seen on my photoblog here – http://www.shanemurphy.ie/index.php?x=browse&category=17
Thanks for reading & have fun.
All images are copyright Shane Murphy