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ZWO EAF Adapter Rings and Focusser ring

Samyang 135mm F2.0 ED UMC ZWO EAF Focuser DIY
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Michael Ring avatar
Michael Ring avatar
In order to use the ZWO EAF with the Samyang 135mm you need a focusser ring to adapt to GT2 belts.



I designed the rings and the EAF holder myself, but the Adapter for GT2 belts can be found here:

https://www.thingiverse.com/thing:4761672/files

It is a tight fit but can easily be made a little wider with some sanding paper

Have fun,

Michael
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Michael Ring avatar
Michael Ring avatar


Here's the design for the Adapter rings:

https://a360.co/42DEtjU

and the STLs for the bigger (80mm) and the smaller (70mm) ring

80mm top.stl 80mm bottom.stl 70mm top.stl 70mm bottom.stl

and the dovetail:

https://a360.co/43zqGMv

Dovetail v1.stl

Print the Dovetail standing on it's small side, this will make the print more stable for claming things into the dovetail.

The knobs for tightening the rings were taken from this model:

https://www.printables.com/model/466697-samyangrokinon-135mm-rings-fine-bahtinov-mask/files
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Nicolas Molina avatar
Nicolas Molina avatar
Hi Michael! Nice setup! I noticed in the photo that you are using the ZWO adapter. I recently purchased the Astro Essentials M48 adapter and was wondering when you started using it. Have you noticed any improvements in star quality in the corners of your images?

CS
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Michael Ring avatar
Michael Ring avatar
I have two Samyangs, one with Nikon Mount and the other one with a Canon Mount.

What I saw is that with the M48 Adapter (which is only available for the Canon Version) the overall stability was much improved so that there is an actual chance to better correct out tilt.

The Nikon adapter is quite flimsy, you can easily move the camera position with a finger and even gravity can cause issues when you use longer cables or have stiff cables that slightly move the camera. The Canon may be a bit better because it has bigger diameter so the effect of the mass hanging behind the adapter is perhaps not that big. But I did not even care to buy one, I first bought the M48 Adapter and after that looked for a reasonably priced 2nd Hand Samyang with Canon mount.

I also found out that mounting plays an important role for tilt, I had versions of my rig where I supported both lens and camera, but this was actually not helping much because it was difficult to get good alignment, so I ended up with only supporting the lens, please see attached picture....

For your setup with the filter wheel I'd imagine that the M48 adapter should be a game changer because you have even more weight hanging at the end of the lens.

I am currently developing a tilt adapter, first started with a 3d printed version, now I have everything to cut Acrylic, so I cannot say for sure that I will end up with close to no tilt with the adapter but I can say for sure that there will be less variability with the M48 Adapter compared to the Nikon Mount

Michael

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Jan Erik Vallestad avatar
Jan Erik Vallestad avatar
Michael Ring:
I have two Samyangs, one with Nikon Mount and the other one with a Canon Mount.

What I saw is that with the M48 Adapter (which is only available for the Canon Version) the overall stability was much improved so that there is an actual chance to better correct out tilt.

The Nikon adapter is quite flimsy, you can easily move the camera position with a finger and even gravity can cause issues when you use longer cables or have stiff cables that slightly move the camera. The Canon may be a bit better because it has bigger diameter so the effect of the mass hanging behind the adapter is perhaps not that big. But I did not even care to buy one, I first bought the M48 Adapter and after that looked for a reasonably priced 2nd Hand Samyang with Canon mount.

I also found out that mounting plays an important role for tilt, I had versions of my rig where I supported both lens and camera, but this was actually not helping much because it was difficult to get good alignment, so I ended up with only supporting the lens, please see attached picture....

For your setup with the filter wheel I'd imagine that the M48 adapter should be a game changer because you have even more weight hanging at the end of the lens.

I am currently developing a tilt adapter, first started with a 3d printed version, now I have everything to cut Acrylic, so I cannot say for sure that I will end up with close to no tilt with the adapter but I can say for sure that there will be less variability with the M48 Adapter compared to the Nikon Mount

Michael


I'm currently building my own dual Nikon Samyang rig using IMX571 sensors. I have one mono with a 2" EFW and have yet to decide whether I go for another one or the OSC version. Do you have any more images of your setup? I'm still trying to figure out how I can best manage to assemble it all but your solution looks solid. Are you getting the exact same FOV?
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Michael Ring avatar
Michael Ring avatar
I will create some extra pics tomorrow.
Getting the two cameras to point at the same place is quite easy, you can first capture one picture each when the two lenses are parallel (in the distance from each other as you need them to be), then you simply plate solve and look at the center coordinates of the two images and split the difference of the angle between the DEC part of the center coordinates. Then you can 3d print a triangle with exactly that angle. You may also manually adjust the aluminium frame until a star is centered in the FOV of both cameras but the 3d printed angle feels a little more precise.
My goal with the design was to get two fields at the same time, this is the reason why the two lenses form a V, to have them point to the same field I'd have to mount them in the other direction and the angle would have to be smaller.
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Jan Erik Vallestad avatar
Jan Erik Vallestad avatar
Much appreciated!
Michael Ring avatar
Michael Ring avatar
Here are some more pictures, let me know if you need anything else

Michael
Marko avatar
Marko avatar
Michael Ring:
I designed the rings and the EAF holder myself, but the Adapter for GT2 belts can be found here:

https://www.thingiverse.com/thing:4761672/files

Hi Michael,

thank you for uploading this, this is exactly what I need.
I also have a general question about using the EAF with the Samyang: On my standard telescope the Asiair is moving the focus back and forth while running an autofocus procedure.
Since the Samyang has its infinity position more or less at the end of its travel range, how does it work with the EAF? I image that there is the risk that the focusser bumps the focus ring into its mechanical limit. I am wondering if autofocus is still possible this way or if I should stick with a manual focus procedure. What is your experiance with that?
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Michael Ring avatar
Michael Ring avatar
AF works just fine, you only need to make sure that your backfocus is tuned well, then you have enough space from infinity to the hard end stop.

Lso make sure that the overshoot is set so that the focused moves from infinity in direction of shorter distance. When you configure it in the wrong way the overshoot movement will hit the end stop.

Michael
Marko avatar
Marko avatar
Thank you, that is very helpful and I will keep it in mind.
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