Crowd-sourcing astrophotography

Images from multiple amateur telescopic images of a given region of the sky can be combined using tools at Astrometry.net to create the equivalent of super long exposures.  The results can be

Here’s an article and paper about this crowd-sources approach to astronomical imagery:

From the article:

The combined image for the M51 galaxies is just as impressive, taking only 40 minutes to produce on a single processor. It reveals extended structures around both galaxies, which astronomers know to be debris from their gravitational interaction as they collide.

Lang and co say these faint features are hugely important because they allow astronomers to measure the age, mass ratios, and orbital configurations of the galaxies involved. Interestingly, many of these faint features are not visible in any of the input images taken from the Web. They emerge only once images have been combined.