Hi,
Surely all system with vanes shows up diffraction spikes, collimation is not transport stable...
As seen on your nice picture, IMO the collimation or the focussing could be aproved. The stars have an eggshape and the starinternal colouring is not homegene. This is pointing out to the two premensioned origins...
In terms of diffraction spikes, these ones shoul be more uniformly visible, like fine crosses...
Best