These photo composites come to us courtesy of astronaut Don Pettit, aboard the International Space Station. There’s a set of 18 on Flickr for your perusal.
Expedition 31 Flight Engineer Don Pettit relayed some information about photographic techniques used to achieve the images: “My star trail images are made by taking a time exposure of about 10 to 15 minutes. However, with modern digital cameras, 30 seconds is about the longest exposure possible, due to electronic detector noise effectively snowing out the image. To achieve the longer exposures I do what many amateur astronomers do. I take multiple 30-second exposures, then ‘stack’ them using imaging software, thus producing the longer exposure.”