hi ernst,
with regards to rahu and ketu prediction, you said they will behave, as their lord ,or the planet they are joined with. so when rahu is with, lets say deb sun (in libra), and Venus lets say exalted, will rahu behave like sun only in rahu/sun and behave like Venus only in rahu/venus if yes , how would we judge its behavior when other antar dasas are present, like for example ,rahu /moon ? would rahu behave like venus ,like sun or any other way?
It will particularly act like its lord in the antardasa of its lord, and of the planet its with during the antardasa of the planet with it. During other times it will always have the energy of its lord, but also every antardasa has the potential to shift that, so if its in cancer in D60 for instance, then in moon antardasa it will really act like moon.
basically, the dasa lord rahu will also give the effects of the lord of its D60 and it will do that in the antardasa of that lord.
rahu is going to have its agenda based on its lord, the planets joining it, it will share that exact same agenda in the antardasa of its lord and the planets joining it. BUt it will have that agenda throughout the entire dasa. So any antardasas of planets that share the same type of agenda will deliver effects relative to that agenda.
its going to do as well in the varga that you are looking at as is the wellbeing of its lord.