Küstner’s Observations of 1884–85: the Turning Point in the Empirical Establishment of Polar Motion

Abstract

AbstractSince Euler in 1765 predicted the possibility of polar motion, the search for an observational confirmation went on. While some indications were found before, the proof without doubt is generally attributed to Küstner. Ironically, the aim of Küstner’s precise observations of 1884–1885 in Berlin was another one, namely an improved value of the constant of aberration. Using the Horrebow-Talcott method, he could conclude that the latitude of Berlin had decreased significantly by 02 in about one year. His findings promoted the start of international cooperation to observe the polar motion. Measurements from Honolulu in 1891 exhibited the effect in counterphase, thus omitting the last chance for a local explanation.