Had first light with the QHY183m and rok 135 F/2 last night. Incredibly happy with my purchase, especially coming from a dslr/vintage lens. However, I had some pretty nasty tilt. It's expected at F/2, but I know I can fine tune it to be much better.
The backspacing is more or less there, however I don't have calipers to check. The main issue is the fact that star size is very uneven, running the FWHM script in Pixinsight shows me that the bottom left has a value of 6.0 and top right a value of 3.0. Top right visually also looks like it has some backspacing issues, but it's probably present through the image and just only noticeable on the more focused stars.
Unfortunately it's cloudy for the next week, but I do want to test out the tilt and try get a flat feild after which I can fine tune the backspacing.
Would it be possible to use a few false stars to test out the tilt. Or does the lens need to be at infinity focus to effectively quantify/test the tilt. Ideally I can fix the tilt for the most part while it's cloudy and then fine tune the backspacing once I can shoot stars and test at infinity focus.
If your curious, in using the QHY 183M -> Small screw adapater -> CFW3-M-US - Blade EF adapter with no spacers. I found that adding even a .5mm spacer made it so I couldn't focus to infinity.
This is an imgur album of the graphs. Top two are the 19*180s F/2 stack, and the bottom one is from a single sub
Https://imgur.com/a/zoj3VjN
