Why does the Ascendant of the composite chart change by 180° if I change the birth time of one of the partners?
The Ascendant in a composite chart can be computed in different ways, depending on the technique the astrologer uses. One cannot look at the Ascendant in an isolated way without considering the position of the MC. We calculate the MC first and go from there. Sometimes a raw calculation of the Ascendant results in an impossible sequence of houses. A change in the birth time of one of the partners may have the same result. This is why the ASC / DESC axis is swapped (by 180°) in such cases. With midpoints, there is always an axis with a near and a far midpoint for each pair of factors. Both midpoints are nearly equivalent in meaning and can be reversed if needed.
