Hi Chris,
You got the framing spot on indeed. Processing can actually be quite fun once you got yourself a flow that works and have familiarized yourself with the "beginner's sins"
One of those sins is clipping your image/signal. I'm not sure what went wrong with JJJ's image (she's usually right on the money!) but it suffers from some severe black clipping.
Another beginner's sin is to 'overcook' your image - not knowing when to stop, getting into a feedback loop of correcting your actions.
If you are sure you want to use PS, then start with a short flow (i.e. just a few essential operations), get to know them inside out, then start adding more of the more esotheric stuff to refine your flow. If you don't want to develop your own flow, steal someone else's - there are a good few tutorials out there.
Be careful with Photoshop 101 courses - they may be great for daytime photography but a horrible starting point for astrophotography as actions that are perfectly fine for daytime photography can completely destroy your precious data!
Best advice of all would be to just keep at it!
Cheers,