Hi Wouter, You've overestimated the distance that two stars must be apart before differential seeing takes effect. The scale is arcsecs vs arcmins. See this post for a really good discussion of this:
www.cloudynights.com/topic/694739-autogu...imultaneously/page-2 (note that you should scroll down to comment #48...to view the most relevant material).
Whether or not our algorithm implementation has correctly averaged the independent contributions of multiple stars is a different matter. In principle however, a multistar guide algorithm should perform better with increasingly shorter exposures. For progressively longer exposures, seeing is of course being averaged out. Whether we can get exposures short enough to cross-over and outperform a long(er) exposure single star approach is TBD. Star constellation geometry and other factors will likely play roles too, so it's likely complicated (of course). In any case, it's a really interesting topic. The testing needed to drive out conditions/constraints where multi-star might outperform single star guiding would be interesting. This is good full-moon engineering time fodder!

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