Hi,
Thanks for the reply!
When I said "I get it" it was more so in the terms of what's actually happening for focus to be reached i.e., how the light focuses and such, I just recently finished my module in my astrophysics degree on Light & Optics so I appreciate that, I was more so confused as to whether the coma corrector will help me reach - or in this case, remove, as you've said, - the required back focus - per say.
What I'm grasping from Barbulo is that I don't need to worry too much as the coma corrector he's mentioned is the one I was looking to get, so if his works fine and he uses a camera with an APS-C sensor, then they should act fairly similarly.