The current HiPS viewer in Firefly has a maximum field of view of 180 degrees, at which point it provides a "looking at the inside of a cut hemisphere" kind of view.

For all-sky query coverage purposes it would be very useful to allow the rendering of a HiPS image (or catalog, in the future) in Aitoff projection (and perhaps other commonly used all-sky projections), integrated with zooming, so that one could start with this "360 degree" field of view and then zoom in.

There is sufficient data in the HiPS data structures to do this; it's a matter of coding the proper projection and of providing the UI support necessary for switching projections.