Good Day Dear Astrophotographers,
After spending years on star trail photography, I made the decision that the pandemic was an good time to expand my interest and invest in a decent camera, telescope, mount, etc. Hence, i bought a used mount, a new ASI533MC, a new Zenithstar 61 II APO with adjustable flat61 for Z61, a Zwo 1.25" filterwheel with Optolong L-Enhance and Zwo Dou-Band filters.
Everything came in perfectly, and I'm ready for some clear skies. However, before i'm going out and about, I'm a bit lost in the back focus measurements. I do understand that Zwo needs the 56 mm back focus, like mentioned on their website (see first attachment). The thing that I'm struggling with is from where to where do you measure, I mean from the end of the telescope of from the end of the reducer? And flat on the surface of the camera or do I need to add a few mm's? And last, I did see on other topics that you need to calculate the filter as well however some users do add 1 mm others 0.3 mm...
I have included a picture of my configuration and I would appreciate it if you could maybe draw in some markers of the start and end of the measurements.
Thanks in advance, I really appreciate your time with reading my post!