I come accross this adapter for my RC8 telescope. It allows for direct connection to the telescope as well as the Takahashi collimating telescope for more precise collimating of the RC8.
I picked it up from the site: https://www.rafcamer...x1f-to-m36-4x1f.
I have seen something similar but not for the 8". I,m sure this would also work on a 6" as it also has a 90mm thread, but can't be to sure about that.
Since I have used it I have been getting top collimation where as before it was always touch and go and I would contribute this to the fact I'm not trying to collimate through the focuser.
You can also attached any 48mm threaded adapter to it as well I attached a laser to double check the alignment.