Hi Richard,
Yeah, it can be confusing! Does the CEM60 have a setting allowing you to switch between J2000 and JNOW?
In general, I find it easiest to leave everything J2000 because most solvers (Astrometry, Pinpoint, etc) use J2000, and the Framing and Mosaic Wizard is also J2000. The gotcha in my case is that my mount only supports JNOW. What happens in this case is that the mount is not technically pointing to where it thinks it is, and that’s ok as long as I have only 1 piece of software (SGP) talking to the mount, or certain everything else is also J2000.
The point you make about RA/DEC/Time is right on - the convention we use (RA/DEC alone) is the problem. Imagine if every computer system in the world used time without any notion of time zone! It’s a similar problem. Ideally, RA/DEC/Time or Epoch would be expected as and it would be up to each piece of software to convert as needed.
Unfortunately, this is not likely to be done anytime soon. AP has made it clear that they have no intention of supporting J2000 as the world would certainly fall into chaos, while other mounts (Celestron, et al) have the option to switch and it’s no big deal. In fairness to AP, they make the valid point that the controlling software should be making the call, as it knows the epoch and intentions of the user, so should handle translations when sending commands to the mount. If your mount supports both, I’d set it to J2000, and have everything else set to J2000 since it is the lowest common denominator. If you don’t know what a piece of software is using, you’d likely have to ask the author.
I think ASCOM has some features built in to do epoch translations. I believe Jared/Ken are looking into this, but I imagine the issue isn’t the math as much as how/where to handle translations.