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The Sciences

Two solar ISS transits!

Bad AstronomyBy Phil PlaitMay 26, 2010 4:23 PM


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I have two more amazing images for you! Both show the same thing -- the International Space Station crossing the Sun -- but in different ways. The first is, once again, from Thierry Legault:


Wow! You can clearly see the station (with Atlantis docked on the left!) as it crosses the Sun. Here's a slight closeup:


There's a nice sunspot pair there in the upper right; the one on the right looks like a face, actually. Cute. This shot was taken at 1/8000th of a second, which froze the action nicely. He has higher resolution pictures on his webpage for this event. The second picture is slightly different:


It was taken by Heiko Mehring and obviously shows a series of silhouettes as the ISS and Atlantis crossed the Sun. You can clearly see the same sunspots, but the path of the spacecraft is slightly different, and the spots look a bit different as well. The equipment Heiko used was less fancy than what Thierry has, but you can still see a lot of detail in the image. It really is amazing that we can see such detail on the station from the ground! I suspect the atmosphere was steadier at Thierry's observing site too; in the images on his page you can see the granulation on the surface of the Sun. Those granules are vast columns of hot gas rising to the Sun's surface, cooling off, then sinking again. It's a grand version of the convection that happens when you boil water in your teapot!

[Update: A third site with a great shot of the transit was pointed out in the comments below. I wonder how many more are out there?]

These kinds of shots take a lot of planning, a lot of experience, and a bit of good fortune (or whatever politically correct term skeptics are supposed to use these days). When I was younger I shot a LOT of film of the Moon, and got maybe a 10% success rate if I was doing well. Digital cameras and the Internet make it a whole lot easier to get spectacular shots like these. I'm glad to see more people tackling these difficult shots, and expect that we'll be seeing lots more like these as time goes on. Tip o' the dew cap to Thierry Legault and Jan Sorg for sending these to me.

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