Has anyone tried this? I believe it works under ASCOM. The USB port on the focuser acts as a serial bridge to the AUX ports. If it works using an AVX (for example), we won't need a hand controller or need to build a HBG3.

I would try this myself but I am in the middle of a rebuild.

To answer this myself. I tested it and it does work. I can slew the mount with no HC attached; only a direct usb connection from an Ubuntu machine running kstars to the usb port of the Celestron focuser attached to my C8/AVX.

This is potentially a very simple and relatively cheap way of getting both automated startup and focuser capability to a Celestron mount.

Note: I observed some timeout issues, but I think that was the driver.