How is a directional antenna pointed when making a "long-path" contact with another station?
Why Radio signals can travel either the short great-circle route between two stations or the opposite way around the world, the long path. Since both routes lie on the same great circle through the two stations, the long-path bearing is simply the short-path bearing plus or minus 180 degrees, and the two distances add up to about 24,900 miles. Long path is worth trying when the direct route crosses harsh conditions such as a daylight polar path, because the long way around may be entirely in darkness or otherwise better propagated.
Watch out The gray line is the terminator between day and night, used for gray-line propagation at sunrise and sunset; that is a different technique, though gray-line and long-path openings often occur at the same times.
Long path = short path plus 180 degrees. Just spin the beam around backwards.