Well I didn't get an answer, I started sorting out on my own.
You can't make M31 there. Only M27, M26, etc.
In addition, a stop ring must be made on the lens so that the lens does not fall inside the NV.
Maxmir, you would post a photo. Who will make it later will be unclear.
For Mod3, you need to solve the issue with the setting to infinity. There is no adjustment on the lens. It is necessary to make an adapter with a greater thickness and cut it off little by little with a milling cutter, followed by a star check.
As a result, experimentally find the required thickness.
Let me remind you that for afocal use it is desirable that the lens be focused to infinity.
To use 1x for me is not relevant. Zeiss Tevidon works well for me. Although options are possible ...
Here is what I made.
Note : I turned down the first 1-2 mm too much.
It exposed some plastic substrate. The lens is still quite solid.
It comes to focus as shown; right where the threads end.
Edited by maxmir, 28 June 2021 - 08:42 PM.