Hmm, geon, you're right - it looks more like a 180-degree fisheye or something than a true mirror-ball map, which contains the entire environment. Alienizer, that might be why you're having a FOV problem
- the map is supposed to be 180 degrees wide, but is being stretched over 360 degrees, hence looks bigger (closer) than it should be. Alienizer, you might try using the fisheye equations from this article and see how well that works.
Actually, it's a skydome. The shot was taken on the ground facing up (90 deg) to the sky, that's why no ground is in the shot. The other equation did not work, but yours does!
It's like this one...
Here is a big image of the skydome as oppose to the thumbnail I posted...
direct linking not allow, so here is the page...