Hendricus Gerardus van de Sande Bakhuyzen (1838-1923) studied engineering before coming to Leiden to study astronomy. He first worked as a school teacher, and after that he was briefly professor of applied physics at the Delft Polytechnic before succeeding Frederik Kaiser as director of Leiden Observatory in 1872. His main scientific work regarded the elimination of systematic errors from astronomical observations (esp. fundamental astrometry), including errors of instruments and personal errors of the observers. He also worked on geodesy (measuring the earth). He was one of the organisers of the Venus transit expedition in 1874-1875, although he did not participate in the expedition himself.

Bakhuyzen was active in several international organisations, including the Astronomische Gesellschaft , the International Geodetic Association and the Carte du Ciel project, although Leiden did no contribute to the photographic Carte itself. Between 1888 and 1900 he was president of the Royal Academy of Sciences.

During his directorate, Leiden Observatory acquired a new 10-inch refractor and a 13-inch photographic refractor. Nevertheless, this period is often regarded as a period of decline. One frequent comment is that observations were published late, if at all.

At the occasion of his retirement in 1908, Bakhuyzen was given a monumental Album Amicorum, containing pictures of hundreds of scientists, both Dutch and foreign. He was succeeded by his brother and student E.F. (Ernst) van de Sande Bakhuyzen.