Luíz Cruls or Luís Cruls or Louis Ferdinand Cruls (21 January 1848 – 21 June 1908) was a Belgian-Brazilian astronomer and geodesist. He was Director of the Brazilian National Observatory from 1881 to 1908, led the commission charged with the survey and selection of a future site for the capital of Brazil in the Central Plateau, and was co-discoverer of the Great Comet of 1882. Cruls was also an active proponent of efforts to accurately measure solar parallax and towards that end led a Brazilian team in their observations of 1882 Transit of Venus in Punta Arenas, Chile. Early life Cruls was born in 1848 in Diest, Belgium, the son of Philippe Augustin Guillaume Cruls (a civil engineer) and Anne Elizabeth Jordens. From 1863 to 1868, Cruls studied civil engineering at the University of Ghent. In 1869 he undertook training as a military engineer and officer, graduating as a 2nd Lieutenant. Cruls served in the Belgian army, attaining the rank of 1st Lieutenant, until 1873 or 1874 (sources disagree). Likely inspired by Brazilian friends at University (including Caetano de Almeida Furquim, a fellow engineer), Cruls resigned his commission and set out for Brazil on 5 September 1874. During the trans-Atlantic crossing on the steamer Orénoque, Cruls met and became friends with Joaquim Nabuco, a journalist and abolitionist, and also the son of Jose Thomas Nabuco, an influential Brazilian politician. Nabuco's connections were to provide Cruls with access to the highest levels of Brazilian society. Brazil, Belgium, and back again Within weeks after Cruls' arrival in Brazil, Joaquim Nabuco and his father arranged for him to be presented to Dom Pedro II, Emperor of Brazil, and more importantly, to meet Buarque de Macedo, the Director General of the Ministry of Public Works. This latter meeting led to Cruls being hired as an engineer by the Commission of the Empire General Charter (Comissão da Carta Geral do Império) in the Geodesy section. In January 1875 Cruls was forced to return to Belgium for family reasons. The Commission took Cruls' unexpected return as an opportunity, and assigned him the duty of assisting the Brazilian ambassador in coordinating the receipt and transportation of geodesic instruments that the Commission had previously purchased. While in Europe, published his first major paper, Discussion of the Methods of Repetition and Reiteration Employed in Geodesy for the Angles. Crul's monograph analyzed the various methods then used to fix geographic