Cosina mount to Ektar Fluro

I have a Fluro Ektar 111mm f:1.5 and decided to mount it to Cosina SLR Body.

When both free , lens set to 5 -10 mm distance from Camera mount. There is nothing at the back of Ektar , bare , polished , brass cylinder where last lens element at the end with 6cms diameter.

How can mount cosina to brass cylinder and also focus when changing lens end to camera front mount distance ?

Umut

Some camera manufacturers had extension tubes with focussing helicals, alternatively I would look for a really ugly standard lens and scrap it for the helical

David

I think I need something like that. Extension tube must be attached to Ektars bare brass tube with squeezing screws. Is there anyone knows what is that interconnection thing ?

Umut

For information , I registered to one astronomy forum and asked the same , more detailed question to Astronomy Film Users section. Answer comes about cnc machining of that joint. Cheapest material , lowest precision option was 350 dollars.
I visited www.meade.com , one important telescope manufacturer , they have k mount for telescopes ,
its 17 dollar but it is so thin , useless. I need least 6 cms extension tube , one side is k mount and other side is larger than the k mount rims outer border, Ektars back.
I think I would buy the k mount ring and glue a one part of the two part PVC tube , opening 4 screw holes to the outer side of the tube which is second part and slide and again screw tight first part to second and use these two parts slides as a focuser.

Its a dinky design but if everything fits together and if I work slow , I can manage to take photographs with Cosina K Mount SLR on Fluro Ektar.

Umut