If we go to higher altitudes like on top of a mountain or in airplane, does it help for moonsighting?
Going to a higher elevation really does not change the situation except for a small time delay added to the setting times for sun and moon. This delay by itself helps very little. However, going to higher elevation helps the visibility, because the higher the elevation, the better is the air transparency, and the lower is the light extinction. But this does not mean that a moon of 10 hours old can be seen from high monutains or even from airplanes.
