Since the ISS is only visible for about three minutes, optimally, you can get between 5 to 7 exposures of the craft as it travels across the sky. The ISS moves from north-west to north. As you're watching the north-west sky, looking for the ISS, its tough to see amongst all of the stars. Then all of a sudden, there it is.
The ISS is higher in the sky than any airplane, and it has no blinking navigation lights, and it doesn't appear to be climbing or descending, as airplanes do. It just moves in an absolutely flat-line trajectory, across the sky in a very businesslike manner. It really stands out from the stars and airplanes, in a subtle yet forceful way.
It appears suddenly, becomes brighter as it tracks from north west to north, and the further north it goes, the closer it comes to the shadow cast by the earth in the light of the sun. As the ISS travels towards the north sky, it quickly grows dimmer, and then suddenly its gone.
I used a wide angle lens to get this series of captures. I wanted to have some foreground, trees and geography, to have a sense of scale and perspective. I had tried to use a 70-300mm zoom last night on the ISS, but you can't get any horizon and provide the perspective that I wanted.
Before the ISS was due to show, I set the camera with a 20 second exposure, and kept the ISO (light sensitivity) setting low (ISO 200); the higher the ISO, the better you can record images at night, but the higher ISO also causes pixilization distortion, adding blots, dots and other color artifacts that make the pictures look rough. The trick is to have a balance of light sensitivity without creating distortion issues.
I found that I had to increase the ISO to 500, then drop the aperture wide open to allow yet more light. The sad thing is that I was unable to make it out to the countryside in time, so there is an orange hue in some shots which is consistent with the light pollution of cities, where the proliferation of artificial light creates an orange haze in the atmosphere.
So, in these shots, I used my Canon 17-40mm lens, which creates some butter-rich landscape shots in daytime. By pre-setting the focus to infinity, I wasn't going to be stuck trying to get the shutter release to go in frustration. Auto focus tries to hunt for a fix in dark skies, and in the dark can't find a point to focus on, so the shutter won't release, or in other words, the picture "won't take." You can be desperately trying to take a shot of something in the night sky, and the shutter release won't work because the auto focus can't find focus! So, I pre-set to infinity, take a few test shots and make sure the results are in focus.
Then, I fine tune the exposure times, aperture and ISO settings so I have a balance between sufficient exposure and clarity. I can get better pictures than these by being out in the country for the next appearance of the ISS.
All shots were 20 seconds exposure, aperture at f/5.6 (would have preferred f/8 for better depth of field, but f/8 didn't create sufficient exposure). ISO was at 500, 17-40mm Canon L series lens, with the camera tripod mounted.
Keep an eye on the ISS visibility schedules. Its worth being outside to see the ISS go across the sky. Its hard to describe, but it just has more gravitas and businesslike mien to it than any airplane. Its very cool, considering that its in outer space, moving at over 27,000 kilometers per hour and there are people in it doing experiments as it streaks across the sky.
Till next time,