International Space Station, Mars and Taurus
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With a little planning and preparation, you can take a photo like this one!
1. Predict the visibility. I go to the Heavens Above web site. Will the ISS be making any upcoming passes over the Phoenix area? Yes! There will be a very favorable pass (almost directly overhead) at 5:15 a.m. on September 9. I download a star chart showing how the ISS will pass across the sky.
2. Check the sunrise. Using a sunrise/sunset table printed out from the U.S. Naval Observatory web site, I note that sunrise on September 9 in Phoenix will be at 6:08 a.m. Therefore, the pass will occur almost an hour before sunrise, and the sky overhead will still be fairly dark. At magnitude -2.5, the ISS will be plainly visible against the dark sky.
3. Plan the background. Will the ISS appear to pass close to any other photogenic objects in the sky? Yes! According to the star chart, as the ISS crosses overhead it will pass fairly near the Hyades star cluster and the planet Mars, and very close to the bright star Capella.
4. Compose the image. Using the Photography Calculators web site, I determine that a 35mm camera with my preferred lens (24mm) has an angular field of view of 73 x 53 degrees. Overlaying this rectangle on the star chart, I see that I can get the Hyades and Mars on one side of the photo, the ISS and Capella on the other. For aesthetic purposes, I rotate the rectangle so that the ISS will make a diagonal streak within the frame -- not parallel to the edges.
5. Calculate the exposure. According to the tick marks on the star chart, the ISS will go from edge to edge of my photo in about 50 seconds; I pick an exposure time of 40 seconds so the streak will begin and end within the frame. 40 seconds is also short enough to minimize trailing of the star images due to the turning of the earth (for simplicity, I'll be using a fixed tripod rather than a tracking mount). Based on past experience, I estimate that an aperture setting of f/2.8 should give the correct exposure with the ISO 100 film I'll be using. The goal is to have an exposure sensitive enough to record the moving ISS, but not so sensitive that the ambient sky glow overexposes the film.
6. Pick the location. Coincidentally, I'll be doing a sunrise mountain bike ride that morning at Usery Mountain Regional Park on the far eastern outskirts of Phoenix; by arriving there early I can photograph the ISS pass with less light pollution than where I live in the suburbs. This will allow more of the background stars to show up in the photo.
7. Set up the camera. On the morning of September 9 I arrive at the park about half an hour before the pass, which gives me plenty of time to set up my tripod, camera and cable release. I rotate the camera until the Hyades, Mars and Capella are positioned in the viewfinder just as planned. I've written down in advance the planned settings for the camera (lens focal length, f-stop, exposure time) to make sure I set them correctly (in the wee hours it can be difficult to think clearly, and easy to make mistakes!).
8. Pray the clouds away. The skies are mostly clear, but occasional clouds keep drifting overhead. Will all my effort be for naught? Luckily the patch of sky I'm photographing mostly clears as the moment approaches; a few wispy clouds linger over Taurus, but not enough to ruin the photo.
9. Spot the ISS. At the predicted time, I turn my attention to the western horizon. Right on time, and right where it should be, the ISS appears, like a bright star moving steadily across the sky.
10. Take the photo. As the ISS passes pre-determined points against the background star patterns, I open and close the camera shutter. When the space station finally disappears in the east, I silently wish the astronauts good luck on their journey across the stars, and give thanks that I was here to see and record their passing.
To find out when the International Space Station will be visible from your location, go to the Heavens Above web site.
Date: September 9, 2007
Time: 5:15 a.m. MST
Location: Usery Mountain Regional Park, Arizona
Film: Fuji Provia 100F slide
Camera: Olympus OM-3 on fixed tripod
Focal length: 24 mm
Aperture: f/2.8
Exposure time: 40 seconds
Scanner: Nikon Coolscan LS-2000