Louis Ferdinand Cruls, Belgian-born Brazilian astronomer and geodesist (Diest, Brabant 21 January 1848 – Paris 21 June 1906)

ACHIEVEMENTS

Determined the rotation period of Mars and measured apparent semi diameter of this planet

Published a memoir about spots and the time of Mars rotation motion (1878)

With E. Liais & emperor Pedro II determined semi-diameter of Sun and Mercury (1878)

Saw the Great Comet of 1882 that was known as Cruls Comet (discovered by English-Australian astronomer Ellery)

Performed the first spectroscopic analysis of comets (1882) by using spectroscope (British William Huggins used photography for the same purpose in 1881)

Proposed formulae for magnetic declination as a function of time

Methode graphique pour la determination des heures approchées des éclipses du soleil et des occultations (1894)

Methodo para determinar as horas das occultações de estrellas pela lua baseado sobre o conhecimento exacto do instante da conjuncção apparente dos dous astros (1899)

Invented a differential barometer

Organized Dictionnaire Climatologique Universelle reckoning on scientists of world renown 

HONORS

Valz Medal, Academie de Sciences de Paris (1882) for his work on spectroscopical analysis in the study of comets

Cruls Crater (in Mars)