How to add "celestial objects" (extremely distant images) that behave correctly I want to add a small moon and a few stars to the background - or at least behind everything, so that it behaves correctly for camera motion. 


Camera rotates around its own axis:  moon and stars rotate about center of FOV
Camera pans (rotates around an axis perpendicular to its own axis):  moon and stars translate. (if you turn your head, the stars move)
Camera moves (translates in (x, y, z)):  moon and stars remain fixed. (if you walk, nearby objects move, but the stars don't)


My animation is technical (think satellite in low earth orbit) so it needs to be fairly accurate. Neil deGrasse Tyson is a major hero of mine. I'll use a normal camera, not orthographic, and I'll use cycles and nodes. I may translate up to 10 blender units and the moon and stars shouldn't move by more than a pixel. 

I could make a very very big image and put it very very far away, but is there a better way? I can generate the stars algorithmically if necessary, so that when the camera pans they move correctly.

Can we define a background (e.g. a sky) at infinity? Can we paint (uv map) on to the "Celestial Sphere"? There is some work on Blendertarium (also here) but I'm not sure how to adapt that technique to handle a scene with nearby objects as well.

Edit: After reading @PGmath 's comment, I realized I should also mention that the moon appears to move relative to the stars over time - roughly it's own diameter every hour. So the moon's image would move relative to the point-like stars.
You can make a hemisphere or a sphere(depending on what you want). Then, use a particle system on it. Use a material for the stars, and another one for the half dome. Make the half-dome transparent too, so it wont get in the way of the stars.