What does this mean...

[Jameedon]

I've ran into this a handful of times and I always wonder why it happens.  When I generate a star mask some of the larger stars masks don't cover the center of the star.  But the mask completely covers the rest of the stars as it should, only the large stars generate this effect. 

Does this mean my focus is off or my scope needs to be collimated?  I have an 8" EdgeHD.

[Carlos Milovic]

Just include more wavelet layers in the starmask process, so larger structures could be incorporated.

[Jameedon]

So this doesn't nessisarily indicate that my scope needs to be collimated?

[Phil Leigh]

No it just means the mask needs to be tweaked to allow for larger stars.
If you use the subframeselector script it will measure the average FWHM of the stars for you and this will give you a good indication of focus... if you have round stars and a reasonably small average FWHM you are almost certainly well-collimated.