M42 macro extension

I tried this old night-vision thing. Minimal distance without adaptor was about 3m, and I wanted to get closer.

I printed Murins adapter, but it was to long for my use. So it was great, that Murin shared the FreeCad file as well. I used it an made a shorter tube - which was still a bit to long - and then the shortest possible (the length of the Threads plus 5mm).