Hi folks, newbie here trying to theorize (and learn) a possible imaging setup, before I make purchases. Wondering if my calculations / options below seem sane to the experienced folks? Haven't yet completely decided on a main camera, but might just start off with one of the Sony IMX571 ones. I have never done back focus calculations before, and based on a few other threads I came up with the following.
This will be for a TEC 140FL on a AP Mach 2 mount.
- Controlling Hub
- Focus motor
- ThirdLynx QuickSync FTX40
- Consumes 1 USB2 port and 1 DC port of UPBv2, attached to the TEC 3.5" focuser
- Guide Camera
- Consumes 1 USB3 port of UPBv2, attached to Optec Sagitta OAG
- Image train
- TEC 3.5" Focuser
- AP S35RFAA Adapter
- AP QuadTCC
- Back-focus remaining 99.1mm
- AP EXT327-18.3
- Back-focus remaining 99.1 - 18.3 = 80.8
- Optec Sagitta OAG
- Back-focus remaining 80.8 - 31.7 = 49.1
- Controlled by UPBv2 focus motor output via RJ45 and not by FocusLynx controller
- QHY CFW3L
- Back-focus remaining 49.1 - 21.5 = 27.6
- RJ11 to the QHY camera
- LRGBHaO3S2 Filters
- Back-focus remaining 27.6 + 01.0 = 28.6 (adding 1/3 assuming 3mm thickness?)
- 2" Filters threaded mount (or should I be looking at 50mm unmounted?)
- Back-focus remaining 28.6 - 12.5 = 16.1
- Consumes 1 USB3 port and 1 DC port of UPBv2)
I haven't yet done a deep dive into the connecting thread patterns and assume adapters will be needed between some of those. So, if I didn't botch the calculations, I will need to add stuff to consume 16.1mm? Other than the adapters needed between them, should I be getting rid of the AP EXT327-18.3 and instead just getting one whole longer spacer, assuming adapters haven't already eaten up the space already? I think I also read in some thread that when getting stuff from precise parts, one should always get few mm short and then fill in with stuff like spacer rings?
Any alternative suggestions welcome for devices too.
x-posted here on tec forums