Askar SQA85 internal filter holder

This is an internal filter holder for the Askar SQA85. Unfortunately, the excellent SQA85 refractor does not have a filter holder on the focuser or its adapter. It would be easy to supply an M48F thread (for 2" filters) to the inside of the supplied M76F-M48M adapter.
Lack of this, I designed this holder so that I wouldn't have to stack and assemble an additional filter drawer. It is clamped inside the M76-M48 adapter between the adapter and the telescope and allows a filter to be screwed on with the M48F thread. It fits well on my SQA85 rear of the last refractor lens, but please measure it before screwing it on for the first time, just to be on the safe side!
The adapter extends the back focus by 0.5 mm, while an additional filter shortens it by approx. 0.8 mm. This adds up to a back focus “error” of approx. 1.3 mm, which does not need to be taken into account with the Petzval design of the SQA series.
The adapter may also fit other refractors in the SQA series with the M76-M48 adap