Thanks to comments from the front thread, I downloaded EzDome and got a hdr background.

By the way, only a part of the background comes out. I want to see the whole background.

so, i changed u and v Scale in the advanced setting, The uv size was not changed.

How do I make it look like a sample?

And I don't know, When I register with the ezdome library, I saved both Inner and Out images to the same file. Is this correct?