Thanks guys for c&c.
Made a quick edit: removed the odd bright curve on the horizon of the asteroid (You still can see it on preview though). At least for me it doesn't look that flat now(:
Really nice. My only problem (beyond the lack of depth) is that the gradient to darkness is perhaps a little too sharp.
The surface looks pretty flat due to the angles of the craters and dunes not curving enough away from the viewer near the horizon. Otherwise, I really like the shading :)
spectacular shading, This is great