1874: Death of Adolphe Quetelet, a few days before his 78th birthday. He was the first director of the Observatory, renowned statistician, inventor of the BMI and known for his statistics on the Belgian population and meteorology.

1950: Death of Jean Verbaandert, astronomer at the Observatory, who, in addition to his work on the meridian telescope, had innovative ideas for applications in the study of earth tides.