From the March 29, 1930, issue

WANTED: EARLY PLANET PHOTOGRAPHS

With the discovery of the planet beyond Neptune, by Lowell Observatory astronomers, many months of observation will be needed before even an approximate idea can be obtained of the orbit in which it is moving. A planet like this moves in the ecliptic, the plane in which Earth itself revolves around the sun, and to determine just where this path is, four different observations, giving its direction from Earth on four different occasions, are needed.