Using Photos of a Sphere to Create a 2D Equirectangular Map?

[waldronate]

The approximate solution is to take multiple views of your sphere from different angles and then convert the approximately Orthographic map projection into a piece of an equirectangular one and merge those together. That's what the blender technique does, but automatically doing the merges.
If you're comfortable using random executables from the Internet and are running Windows, I wrote a program to change map projections for images somes years back. Download and install http://fracterra.com/ReprojectImage.zip on your windows machine. Then process each frame ( you'll need at least six images with four around and one from each pole), starting from Orthographic. You will see a preview with the stretched partial images (one image can cover at most one hemisphere, but it will probably not quite be right because you probably don't have a telecentric lens system). After you get your images processed, align in Photoshop and you're done.

[gkoch1]

Thank you for the further explanation. It makes more sense to me now. I will try to replicate your steps. I can’t use your program, though, since I’m on a Mac, but I appreciate the offer. Maybe could do it with Wine. Hmm. Either way, I’ll keep practicing.

And for what it’s worth, the reason I’m doing all this is because some mineral spheres have really cool natural structures in them that resemble coastlines on a planet, and I thought it would be cool to make maps of them.