The ISS and Space Shuttle Atlantis Overfly Boston
On Sunday, the Space Shuttle Atlantis, on it’s last mission (STS-132), docked to the International Space Station (ISS). At dusk, local time, both craft, long since coupled together, flew over the skies of Boston. From my vantage point looking south, they appeared 30 degrees off the horizon due west. And since Boston was to the south of me, they flew overhead and then down towards the skyline. Both craft had passed overhead the night before, but it was cloudy and there wasn’t a chance to see them.
Armed with my new camera, the awesome Canon EOS 7D, a tripod and remote cable, I headed to Skyline Park in Arlington, Massachusetts to watch the transit. Skyline park is known locally as Robbins Farm Park as it is part of the site of the old Robbins Farm. It’s a stunning location – one of the undiscovered gems of the Boston area. It even has a playground with two-story slides. The hill drops off sharply, leaving a dramatic view of the Boston skyline.
Sunday night proved to be almost perfect, with clear blue skies and only a moderate breeze. That’s important, because a strong wind can blow the camera around. When that happens, the ISS/Shuttle that should register as a line in a long exposure can sometimes look all wiggly. Not in this case.
In order to minimize any vibrations, I also locked the mirror up using the custom functions of the camera. When the mirror flips up, it can introduce a tiny amount of vibration. It might not register if you were shooting a long exposure of a still life, for example. But when you are shooting a needle-thin light trail from space craft, it will show up as a series of bends, or sawtooths, in the line.
Here’s what the transit looked like when the ISS/Shuttle were overhead. As you can see, I pressed the shutter when the craft had already entered the frame. I had to manually judge when the craft exited the frame and I was pretty conservative, so I probably could have gotten away with less than the 17 seconds required for this shot.
But this is the shot I’d been hoping to get – the ISS/Shuttle overflight and the Boston skyline all in one frame. Luckily, this time the shuttle did fly close enough for me to make that happen. Although I took a second photo right after this, the ISS disappeared shortly after taking this photo, so I wouldn’t have gotten much longer a trail even if I’d left the shutter open longer. Note that the sky is darker because I’m facing away from sunset as opposed to above where I was pointing the camera up in the sky and picking up some residual light.
You see, the ISS doesn’t generally appear right on the horizon. The reason for this is that it’s close to the earth. If you could see the ISS down a few degrees off the horizon, it would actually be extremely far away. This is because of the curvature of the earth and light-blocking effect of the atmosphere. When the shuttle disappeared, the point of light was actually not moving down towards the skyline – it was actually moving away from me. So the vertical motion was very slight. The point of light just moved increasingly slowly down, but got smaller and smaller (and hence dimmer and dimmer) as it moved away through the atmosphere. Remember, it’s only 200 miles up or so.
Even though the Space Shuttle is being retired, there will be many opportunities to watch the Space Shuttle fly over in the years to come. I encourage you to take advantage of them – it is a surprisingly exciting sight.