Well, the Theory of Relativity is only 96% right in being able to predict where Mercury will be.

The way we do it is that we know where it was, and its period, so we compute that it will be there again, in one more period.
They used to have books with tables, and you would have to extrapolate in between points to make a star chart.

And we have serious problems with the stars in the south breaking the model.

In this area, all i can say is, "I don't know" because you look to deeply in any direction and everything falls apart.