Sunday, March 4, 2007

Chasing Iridium Flares

While my mount is away getting worked on (more on that later) I am looking for other things to image. Iridium flares are something I try to catch visually when I can, but I haven't tried to catch one with the DSLR. What are Iridium flares? They are reflections of sunlight off one of the 66 or so Iridium communications satellites orbiting all over the earth. They have large antenna arrays made of aluminum treated with silver-coated Teflon. Thus, they are highly reflective. The satellites are maintained at a fixed vertical position relative to the earth as they orbit, so if we know the position in orbit, we can use software to predict when and where we'll see the glint of sunlight off the antenna panels. You can check the next times for flares at the Heavens Above website. They require some careful planning to catch with a camera, so use a planetarium program to see where the satellite will be at the time of the flare. Even then you don't always get it right, as you can see by my image. I was a little low with the camera. Fortunately there's always another Iridium flare in the near future.

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