Bill,
Do you have a link to John Rista's comments? My experience is quite different. With my TEC180 at ca 2.11 arc-sec resolution (OAG guider/ultrastar) I can get a huge benefit from dithering 2 pix (with my imaging camera at .88 arc-sec.). This is enough to remove hot pix. Perhaps not enough to remove large artifacts such as aircraft trails. It's an interesting question to consider.
Graham,
There is software that will allow for dithering one camera while synchronized to a different camera (but not 2 other cameras). It only requires that the subs are of equal length, or that the master camera is some multiple in length of the slave camera. It will introduce a delay and even change filters in the slave camera. It works with TheSkyX or TheSkyX + CCDSoft:
http://astro.neutral.org/software/as...-software.html
Peter