[bojan]

Results of test from last night are attached.
While the contribution of the filter to LP extinction was somewhat disappointing (~50%... but still significant), the focus is drastically better.
However, some stars on the image are still bloated (halo is greyish), I think this may be due to presence of IR.

BTW, I returned Rocolax UVIR-cut filter to seller, they promised to send me back the correct one (hopefully they will perform some tests to ensure that... ).