

Don Pettit's Incredible Photos of “Star Trails" - kator
http://www.slate.com/articles/health_and_science/science/2012/06/astronaut_don_pettit_s_photos_of_earth_from_the_international_space_station_.html

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kator
Flickr stream:
[http://www.flickr.com/photos/nasa_jsc_photo/sets/72157629726...](http://www.flickr.com/photos/nasa_jsc_photo/sets/72157629726792248/with/7257865460/)

"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.”

