Hi
On the Spring and autumnal equinoxes, the angle of the sun over the equator is 90 degrees, that is straight overhead, it casts no shadow. In Macapa, Brazil, on the equinox the angle of the sun is 90 degrees whereas Quito, Ecuador the angle is 89.9 degrees. Its the same for Libreville, Gabon also on the equator: 89.9 degrees. Why are they not at 90 degrees on the equinox like Macapa.