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I’ve been working on a wide field build. Currently, I’m using a Zeiss Milvus 135 stopped to f4 with an zwo EFW and asi6200mm the results have been pretty interesting so far, but I’m really struggling with tilt. The lense is connected via an f mount to m54 adapter from zwo. I can’t see an easy way to include some sort of tilt adjustment device with the limited back focus. how have you all handled this? I’m thinking of designing a custom replacement for the f mount on the lens since it’s dedicated to Astro cams. |
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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. |
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Nick Grundy: There are these tilting shims that might just be the ticket (and I'm gonna try them out soon): https://astrodymium.com/collections/frontpage/products/rotating-tilt-adjusters |
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andrea tasselli: 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 |
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The Baader Tilter requires up to 10.5mm of backfocus besides the obvious fact that it was designed for a different flange so a bit of work there to make it work. Gerd Neuman TCU instead would take up 11.3 mm (out of the 14 mm available) of backfocus while allowing mounting the mating Nikon flange from the ASI Nikon to EFW adapter. I think you only need a M54 gender changer. Or you remove the Nikon flange from the Milvus and put in an M54 adaptor, that should save some space... https://www.baader-planetarium.co.uk/shop/baader-ufc-tilter/ |
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| This post of mine at CN years ago might help: https://www.cloudynights.com/topic/680552-supporting-modern-heavy-fast-camera-lenses/ |
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Kevin McCarthy: thanks Kevin, good read. It's pretty much confirming what I was worried about. High-speed + full Frame = tilt issues showing. I think my current issue might be weight induced tilt to some degree but since I'm supporting the lens fairly well its likely more (the Zeiss design really doesn't lend well to a standard ring design) I had to custom print a mount setup before of the EFW anyways, so I'm thinking that replacing the Nikon Flange with a custom designed M54 stainless steel or aluminum flange will get me enough room to use on the of the off-the-shelf tilt adapters listed above. (or I have to design that in as well) I'm just thankful I got to try these wide field lenses and discover a whole new world of technical challenges :-) (pics of the current mount setup. need to add a ring support for the camera side as well i think)     |
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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 |
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andrea tasselli:Nick Grundy: Genial solution, much simpler than a mechanical tilter, when applicable. Thanks for showing it, Andrea! |
