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A wide swath of the Milky Way in the constellations Serpens and Sagittarius shows the effect after the author dithered, aligned, and combined 12 wide-angle shots from a digital single-lens reflex camera on a mount he moved slightly between each exposure.
Tony Hallas
Within the context of astroimaging, dithering our images means moving them around slightly between each exposure. And a good reason exists for us to do this.