I was seeing this odd diffraction pattern last night when my ASI 294 was attached at prime focus to my Evo 8. I am used to the typical 4-quadrant spikes but this is new to me and I have never seen it when using the same equipment with my HyperStar.
I know the colimation is off a bit as central bright spot is not completely centered but I am not too worried about that. This was only visible on very bright stars like Sirus or Betelguese.
As far as I know there really isn't any internal structure inside the OTA to cause this, or is there?