I am using Windows XP and a GeForce 2 graphics card.
Under Celestia 1.3.0, lunar shadows on Earth course funny jittery effects on hexagonal portions of the Earth, apparently changing every frame, with bizarre noise patterns occurring. This effect is visible at all distances. Ring shadows do not have an effect, nor do moon shadows on other planets (e.g. the Galilean moons on Jupiter)
Under Celestia 1.3.1pre11, all shadows on all planets cause this effect, although there is a distance cutoff, e.g. for Saturn it is somewhere around the orbit of Tethys. It is very irritating if I want a nice image of Saturn from, say, Enceladus, when the ring shadow is flashing bright and dark in random patterns.
Turning off atmospheres under Celestia 1.3.1pre11 removes the effect, however this has no effect in Celestia 1.3.0.
Anyone got any ideas what's going on?