The core of the F-Ring (Natural Colors; credits: Lunar Explorer Italia)

Caption NASA:"Structure in the tenuous F-Ring can be seen in this image of the ring's bright core.
Much of the structure in the F-Ring is created by its two shepherding moons: Prometheus (about 86 Km, or approx. 53 miles across) and Pandora (about 81 Km, or approx. 50 miles across).

The image was taken in Visible Light with the Cassini Spacecraft narrow-angle camera on Dec. 8, 2008.
The view, which looks down from about 70° above the Ring-Plane toward the unilluminated side of the Rings, was acquired at a distance of approx. 613.000 Km (about 381.000 miles) from Saturn and at a Sun-Saturn-Spacecraft, or Phase, Angle of 77°.
Image scale is roughly 3 Km (a little less than 2 miles) per pixel".