Even though my Astrodon filters say they are par focal, the Auto focus says differently.
This seems to be a common misconception. If you try the Astrodon filters (or most other filter brands) on a telescope with all reflective surfaces there will be no difference in focus across the full colour range. The moment you introduce any refractive elements there will be some colour dispersion and focus will be different across the colour range. The reason you pay big money for high end refactors and correctors is that they minimize this colour dispersion and the focus between colours is very close. In effect it is the telescope, rather than the filters, that is not 'parfocal'.
Clear Skies
Mick