"Have i undestand this right: Onos is orbiting Trey+Patru and Tano+Sitha and the red dwarf star Dovim."
Right, all of them, except Dovim, is heavier than Onos.
Regarding Dovims position, yeah it is probably in a binary Orbit with Onos. I think that is the case because Dovim shine bright enough on itself to make observation of the stars (others stars than our six chosen ones) impossible to do with the naked eye, so it should be pretty close (I am ignorant in the field of astronomy, so take my guesses with a handfull of salt). However, if that is the case (with that binary orbit) Kalgash doesn't orbit outside of it, as Onos and Dovim do not necessarily appear in the sky at same time (it still happens, just not every day).
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