I’d suspect “absolute” position with an SCT is a “relative” term
The reason is, your just slopping the mirror up and down the baffle tube. It might be precise enough, but depending on how gloopy your baffle tube lube is, I’d reckon it isn’t wildly repeatable.
Celestron sell a stepper-based motor focuser for their SCTs, connects via USB and includes an ASCOM driver. The same problem remains though.
I fear an additional focuser on the visual back is you’re salvation - although if you’re imaging, do your sums carefully when it comes to your back focus.