Now I feel pretty stupid...
It seems I had a problem with tube mounting.. I used a spring-loaded belt around the MTO tube (close to where main mirror is located) that holds it in the cradle... and this belt was too tight !!!
When I released it almost completely, the astigmatism virtually vanished in 12mm eyepiece.
So I was struggling with ghosts..
Thank you all for your replies.. they definitely made me think.
And the end result is, now I do have much better MTO-1000A, it is better than it ever were (because the relaxing of optic contributed as well).
Despite its looks like it is build like a tank, it is still not rigid enough and it is easy to "pinch" the main mirror from the outside!
And now I remember I was reading about this on one German website, but I thought this can not possibly apply to my older and heavier model.
