Normally I'd say this belongs in yt, but this takes care of things specific to spectralcube, for example stretching of the spectral axis, and makes assumption about the WCS order, etc. It also allows the center to be passed as world coordinates. So this isn't just a a plain set of yt commands, it does do additional things specific to spectral cubes. I think to_yt should not run this though (that should be the above function) but we could keep this one as a convenience for fast rendering until yt provides equivalent functionality.