Originally posted by RobG ...has there been a real world impact of the accelerator on astrophotos or night shots with stars on the K1?
The K-1 does not feature an "accelerator unit". The K-1 II's "accelerator unit" does not eat stars (like some Sony models did) but its image processing (starting at ISO 640) will destroy some information that exists near the noise threshold.
For a single exposure or "shallow" stacks of images, the K-1 II will produce more pleasing results. For deep stacks (64+ or so images to be combined), the K-1 should produce images that retain some finer detail. As far as I know, nobody has confirmed this with an experiment, though.
Having said that, astrophotography can require rather low ISO settings to avoid overexposure at wide apertures so the K-1 II should still be as good as the K-1 for many astrophotography applications.
The K-3 III, however, has been announced to apply image processing starting with ISO 100. Although I'm unaware of any concrete information as to whether the processing of RAW files will be optional, the expectation has to be that it will be mandatory. Although the latter policy forgoes the possible "win win" strategy of giving everyone the option they prefer and would in particular avoid negative press from the likes of DPReview, it might be a matter of pride for Pentax to not allow the processing to be optional. Having the scheme mandatory certainly helps nurturing ideas of the processing to be anything else but in-camera post-processing that does not benefit from any information present during capture only.