ISS Pass, March 25th

It’s been a while since I did one of these, partially because the orbital mechanics haven’t lined up for evening ISS passes for a while over Southern California, partially because when they did it’s been cloudy, and partially because I haven’t had a whole lot of spare time available for any of this.

Tonight it was mostly clear, there was a nice pass, and I made time.

Again, using StarStax, a very nice freeware program, to combine multiple short exposures. I could do 30 to 60 second exposures, but with the light pollution they would be all washed out and way too bright to show the ISS trail. Instead, I take a whole series of much shorter exposures (these are all 3 seconds), firing the next shot off as soon as each one is done.

To track when an ISS pass is coming up (or other satellites) I use Heavens-Above, a wonderful website. (You should as well!) Here’s their map which you can match to the photos – rising in the west at the right, headed up toward the top left:


There she is! Coming up from the horizon in the west at the lower left, heading up through some passing clouds. Again, each “dash” is a three-second exposure.

One thing I need to work on is what the field of view is for the camera. These images could have fit into the previous field of view, but I thought that it might be moving out to the right, so I shifted the camera.

Another happy result from stacking the photos is the way it brings out the stars, even with the street lights and light pollution. The Pleiades cluster is just above the ISS’s track in the middle left, above the lens flare from the street light.

Of course, above LA there’s more than just the ISS moving overhead. Here the ISS was just above its apex and starting to sink back down toward the north-northeast. In the lower right of the photo you can see the distinctive “red-green-red-green-red-green-red-green-red-green-WHITE” pattern of an aircraft.

Moving almost due north, from our front yard we have another street light to deal with, and another plane way off to the north just starting to come up over the horizon.

And there she goes! Wave to the six astronauts and cosmonauts on board, Expedition 55! Check out the free available apps from NASA, ESA, and others, as well as sites like Heavens Above! Know when the ISS is coming over your area in the evening (or morning, if you’re one of those people) and see it for yourself!


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