Backfocus problem solving

[mcbras]

Hello,

after reading so much stuff about backfocus, I get confused when it comes to realize what I have to do to make my setup work. Can somebody please validate my thinking:

Equipment:
OTA GSO 8'' 800mm focal length (f/4)
Baader coma corrector RCC I with 94.5mm back focus
FW AFW-90R from Apogee with 29.2 mm thick but I consider 28.2mm due to filter in there
CCD Apogee Altair F8300 with back focal distance of 26mm

Now, the setup it's still not working, I keep getting coma, but I understand why. If the light out of the corrector will be in focus 94.5mm behind it, I need to add a 40.3mm extension. This makes sense, correct?

But now, I'm looking to add a rotator, in this case a OPTEC PYXIS 2-INCH GEN3 which takes 41mm of focus.
I really don't see if this will work or not, because I'm assuming the rotator it's simply a tube that will have the whole optical train attached and will rotate under a certain axis.

Can you please clarify me on that?
Thank you so much!!

[MarkAR]

Maths look correct, so you'll be 0.7mm over with the rotator and no extension.

Depending on how accurate the optical measurement given for the coma corrector back focus is I don't think you'll have a problem.

[mcbras]

Mark, thanks for the reply. Due to the current setup, I will abandon the rotator idea.

Now, I need to do my custom piece, nose piece type to attach my Baader RCC I corrector (M42) on the telescope side and to attach an Apogee AFW 50 9R on the camera side (2''24 thread). Ran the math and I arrive at 37.2mm. First, I guess I will keep like 1 or 2 mm shorter to have room to fine tune it if needed. Anyone sees issues with it?
Went to preciseparts.com and although they have the equipment listed, the final prototype is so huge that i can´t the part in a 2'' focuser tube. Any idea how I can connect the above-mentioned items with a single custom piece?

´Thanks!