I can get you this far, but you'll have to map the image to how you want it: Create your scene, or sky dome if that's what you want. In the center of the scene, that is, where you want the view point to be from, create a sphere that is 100% reflective, 0% refraction, pretty much 0% everything else. Put the camera directly above the sphere, and pointed at it. I'd enter the numbers manually, it's easier and more precise. Render. Now, render an object mask of the sphere and use it to single out the sphere in an image editor. Voila. You have a sky dome completely rendered in Bryce.