Yesterday evening I was traveling around Jupiter's Galilean moons and I discovered that Europa and Ganymede virtual textures from "jonhvanvliet" have a small misalignment if compared to medium resolution textures or "dds" textures.
If you switch the texture resolution by means of the "r" and "R" keyboard command you can witness that Europe and Ganymede images "jump" a little and the effect is more visible if we superimpress a "grid" (from selden, if I remember well
). Forgot to say that obviously the time is paused (pressing the keyboard "spacebar") .
I photographed the situation with some screenshots.
For Europa we have (using VT textures and a .ctx file)
[img]http://piellepi.web-gratis.net/files/johnvanvliet/europa-ctx.jpg
[/img]
while using medium size resolution
[img]http://piellepi.web-gratis.net/files/johnvanvliet/europa-medium.jpg
[/img]
For Ganymede we have, respectively
[img]http://piellepi.web-gratis.net/files/johnvanvliet/ganymede-ctx.jpg
[/img]
and
[img]http://piellepi.web-gratis.net/files/johnvanvliet/ganymede-medium.jpg
[/img]
As you can see the difference is appreciable because of the presence of normal maps that add a white "ghost"
to the first and third image (the VT ones), while in the second and fourth images everything is ok (apart from the worse resolution 
).
The .dds versions are correctly aligned (but I forgot to make snapshots
)
The fact is more evident if you analyze the pictures (the VT .png files and the .jpg medium res and .dds high res ones) in an editor (I use Paint Shop Pro 8 ) : zooming here and there around a certain "pattern" of the satellite's ground features (near the left border of the texture) you can see that the VTs are misaligned.
Now the question arises in all its magnificence!
Which are the misaligned textures and which are the correct one? The virtual textures from john van vliet or the other?
I am quite confused...
BTW Callisto and Io work very well and there is no jump at all.
Thanks for your attention!
Good bye
Pierluigi