precison: Uranus, photographed by Voyager 2, 25th January 1986.
A section of the planet seen in crescent phase. The grid of dots are reseau markings. Voyager 2 used vacuum tubes for imaging (a Vidicon system, essentially like an old CRT monitor, but running in reverse to turn an image into data) which could create distortion around bright areas of the image; the fixed grid of reseau markings allow distortion to be measured and compensated for. Modern space probes use digital cameras (CCD imaging) which doesn’t have this problem - hence no reseau marks.
Image credit: NASA/JPL.