Thanks Nawrot.
Yes we need a kind of warp speed effect, but this effect is caused by the velocity of the ship.
So if the ship doesn’t move, we just see the stars with no tail effect.
When it moves, then we can see the stars’ tails, and depending on his velocity and orientation, the tails will be longer and orientated to the same direction that the ship is.
The postprocess volume may be perfect excepted that it’s applied to all the moving objects, and we want it just to the stars.
Someone had the same issue with his GUI blurred depending on the motion blur, and he fixed it by adding it to a different renderpass. That’s an approach that I have to try too.