Help! Focusing Issue with Bahtinov

[Anthony RS]

Hello,

I'm using a Bahtinov mask made for a 6 inch aperture on my 6 inch F4 Newtonian. However, The Central spike doesn't appear to be straight. I'll share an image I drew to simulate what I see. What could be the cause of that? Is it a bad Bahtinov mask or something with the optics? The star is in the center of the frame.

[MarkAR]

Not seen that before, at a guess maybe your collimation is off.

 

[globular]

If you turn the mask over does the odd effect flip too (which might suggest a dodgy mask) or do you get the same effect with the same orientation (which might suggest collimation).

[Anthony RS]

3 minutes ago, globular said:

If you turn the mask over does the odd effect flip too (which might suggest a dodgy mask) or do you get the same effect with the same orientation (which might suggest collimation).

hmm I'm not entirely sure but I think it always the same effect no matter the orientation. I never knew collimation error could show in the spikes 😕 although collimation looks fine with my collimation tools.