[Wavytone]

Hi Bojan, some years ago I had the MTO version, identical to the one in the photos shown in the link to that german page, and I had completely dismantled and stripped mine down to have the mirrors recoated and resprayed the exterior metalwork as mine really needed it.

In the MTO version:

Dismantling the rear of the primary cell, the primary is held in place by its perimeter - a compression ring around the back side of the mirror presses it up against a shoulder in front of the primary. This compression ring is a ring of plain aluminium with some slots cut in it to allow some springiness (its less than 1 mm) in the axial direction.

Unscrewing the back of the primary mirror cell should expose a threaded ring that adjusts the compression ring.

The compression ring is critical - if its too loose, the mirror will flop around, if its too tight, the force on the primary will distort it (pinching or astigmatism will be visible in images) or worse, you could chip it. By trial and error I found the threaded retaining ring it should be only firmed up with 1 finger - any more than that will apply too much force and deform the images.

In the MTO version the long conical central baffle screwed into the back of the mirror cell - the primary mirror isn't actually supported on the baffle. The front corrector on mine also wasn't a single meniscus - it was actually two menisci making a snug fit with a spacing shim - truly massive amount of glass. The secondary mirror was aluminised on the back of the first (outer) meniscus and the second meniscus had a conical hole drilled in it too. There was also a doublet correcting lens in the baffle, the surfaces had a pale straw-yellow coating.

The focussing is via a simple helical thread cut into the two tube sections, the front part (with the menisci) screws into the rear half. When I first acquired the lens it was lubricated with nasty molybdenum grease, buttery smooth but like yours the focus would NOT stay put. After the restoration work I ended up using ordinary vaseline to lubricate it - this was smooth enough yet enough friction remained that once focussed it would stay put all night.

At the back end mine had a brass plate with a Pentax thread firmly attached (6 screws) so no need for adapters.

While resolution was excellent (good diffraction pattern) the menisci were not coated and the result was the overall transmission through the lens was only 50-60%; I hope yours is better than that !

Have fun !