The problem with the mats out there is that they dont feel 3d. (and they all look like those posters from the 80ies)
I am thinking about doing an experiment with latex.
The plan ist to pour black latex over some fabric and add light blue paint in it to create stars.
When it is dry, I paint another layer of thinned out black latex.
If it works, it will look like the stares are actually in a distance.
(it might be more layers with stars)
But I think it must wait until its hotter outside:)
Another thing is that planets either are to sharp or to faar away.
If the planet is so faar away that you can se the whole planet, then it should not be as sharp as the ships.