Addressing tilt with a wide field camera lens

If you think that it may be something in the lens itself that is off you can send it in to Zeiss for evaluation and repair. https://www.zeiss.com/consumer-products/us/service/repairs/photo-lenses/non-warranty-repair.html

Another thing to consider is proper lens support. The Milvus is heavy lens and normal camera bayonet mounts are pretty flimsy, it may be sagging a bit introducing tilt. I know my otus lenses definitely bend a bit from their own weight.

andrea tasselli:
https://astrodymium.com/collections/frontpage/products/rotating-tilt-adjusters

I actually order these and tried them out. They seem to work well, although they introduce additional backfocus to the train. I also ordered these, and while I didn't need them, but they were nice https://agenaastro.com/blue-fireball-9-pc-fine-tuning-spacer-ring-set-for-m54-threads-0-1-to-1-0-mm-s-set9.html

From what I can tell, I will need to find another mechanism from attached the F mount nikon lens to the ZWO EFW. All the adapters out there seem to provide an exact distance of estimated backfocus, but don't allow any space to reduce or utilize the shims. 

I'm guessing now, but I'm thinking a custom aluminum adapter to fully replace the nikon F mount on the lens is viable. Then I can hopefully utilize an off-the-shelf tilt adjuster that is accessible while the image train is connected (instead of the paralell access that a lot of them seem to be). Just looked at the Baader UFC tilter and it seems like an option. 

As best I can figure, I have about 15.5mm of spacing if i directly attach an m54 of m48 adapter to the Zeiss lense. If I can use ~4-5mm on that, I would have enough space to utilize the baader tilter

Feels like a rough design

This post of mine at CN years ago might help:  https://www.cloudynights.com/topic/680552-supporting-modern-heavy-fast-camera-lenses/

My old QHY camera uses a dovetail/rotator to attach through my spacers and bayonet connection.  I have dealt with tilt on all of my optics when using this camera.  But now that I have committed to my Rokinon 135, I spent a good deal of time solving the issue.  A while ago I thought I had it solved by placing a bit of plastic electrical tape on the dovetail receiver side.  But when I rotated the camera, tilt showed up again.  Two nights ago, I solved the issue by transferring the tape to the camera side of the dovetail.  Same position as it was but on the opposite side of  joint!  Now when I rotate the camera, the tape moves with it and the tilt issue does not return.  Bottom line is that my favorite camera has suffered from a tilted sensor the whole time.  Tapes of different sorts and thicknesses can make useful shims.  And it may be important, as in my case, that the tilt-shim stay fixed in place. A very thin tape can be used to test for optimal thickness by adding several layers.  Once determined the tape shim can be measured with a micrometer so a very precise 'permanent  tilt-shim can be ordered.  And this is inexpensive to do.  

I think the super sensitivities of these short wide lenses made my situation pronounced enough to make me deal with it.  When I then transferred my newly shimmed camera into my f/4.2 refractor the image produced was essentially perfect.  Got perfectly concentric diffraction image out of focus, even well away from image center, and stayed that way when rotated.

Alan