The Total Solar Eclipse of 9 May 1929: The British and German Expeditions to Pattani in Southern Siam

A total solar eclipse occurred on 9 May 1929, and was the third total solar eclipse observable from Siam (later named Thailand) following the celebrated eclipse of 18 August 1868 and the eclipse of 6 April 1875. The 1929 eclipse was of long duration, approximately five minutes along the central line, and because of this expeditions were planned by astronomical institutes from several European countries in order to carry out photographic and spectroscopic studies of the Sun’s corona. One of the primary objectives was to re-confirm Einstein’s Theory of General Relativity following Sir Arthur Eddington’s observations of the total solar eclipse of 29 May 1919.