I'm trying a night scene with a starry sky and using a jpeg of a starry sky but don't know which to use it in... the backdrop or background.  I've tried it in both and can't really see anything except dark sky.  Since I've never used either before and the manual isn't very detailed when it comes to things like this, anyone have any suggestions?

Thanks!

The background is what is seen in reflections and is the image behind the camera.  The Backdrop is where you would insert an image to appear behind the scene, in front of the camera.

If you put something in the background, it will be projected onto a sphere that surrounds the camera. For example, if you put a bi-gradient into the background, it will show up in any direction that you point the camera. I commonly put a bi-gradient into the backdrop as it is also used for gi calculations. The backdrop is different. If you put something into the backdrop, whatever you put in there will be stretched into the backdrop of your render regardless of camera position, angle, or image render size. So, if you have an image that you want to exclusively be in the back of your image, then put it in the backdrop. I commonly put a white gradient into the background for GI lighting and a starfield map into the backdrop for my outer space renders. That allows me to get more filled and realistic lighting while "being" in the blackness of space.

Thanks for your suggestions.  I've played around a bit and for now I've got a star-field in the background and it seems to be working fine for what I need.  (I still had the atmosphere on previously... that's why I wasn't seeing my stars.  Doh!)

Yeh.  The Atmosphere settings can do that.  Which is a royal pain in the backside sometimes when you want the backdrop to show with atmosphere in between.

Guys, thanks for the info.  I can get some pretty neat ship hull effects by placing say a country scene onto the background (takes playing a little with it so it doesn't look like a reflection of a country scene.  Hmmm might be a good way to add grundge.  Jan

I'm only a month late, I'm improving =P

Did you try a sky dome?!? You can render out EXACTLY the kind of sky you have in mind and then use a skydome...

Just a thought...