Between Saturn and the lit side of the Moon is the dark side of the Moon, not visible in the image. In the second image, the dark limb of the Moon has moved across part of Saturn, so that only about half the planet is visible. In the third image, the Moon is fully occulting the planet. The final image shows Saturn and the Moon shortly after Saturn reappeared, as the Moon continued its rapid eastward motion, which carried it past Saturn. The exposure times were 0.08 seconds for the first three images, and 0.01 seconds for the last image.
North is up and east is to the left.
The CCD used had a 192x165 pixel array. The exposure time was 0.02 second. A region of imact is discernable in the southern hemisphere.