The comet Hartley 2, photographed by Deep Impact as part of its extended EPOXI mission, 4 November 2011.
The original photos from this encounter were blurry (I’ve uploaded an almost equivalent gif here for comparison) because of a problem with the lens.  By pointing the camera at a star, effectively a point-source of light, and studying the precise way in which the point got blurred, the EPOXI team was able to work backwards and “deconvolve” the photos of Hartley 2.  This procedure makes them much sharper, but also introduces some ringing artefacts, which are especially visible in the first few frames.

The comet Hartley 2, photographed by Deep Impact as part of its extended EPOXI mission, 4 November 2011.

The original photos from this encounter were blurry (I’ve uploaded an almost equivalent gif here for comparison) because of a problem with the lens.  By pointing the camera at a star, effectively a point-source of light, and studying the precise way in which the point got blurred, the EPOXI team was able to work backwards and “deconvolve” the photos of Hartley 2.  This procedure makes them much sharper, but also introduces some ringing artefacts, which are especially visible in the first few frames.