
Hendricus Gerardus van de Sande Bakhuyzen (April 2, 1838, inThe Hague – January 8, 1923, inLeiden) was a Dutchastronomer. His surname, van de Sande Bakhuyzen, is sometimes erroneously given asBackhuyzen orBakhuysen. His first name is sometimes given asHendrik Gerard.
He studiedastronomy underFrederik Kaiser.After he got his degree, he was a high school teacher from 1864–1867, during which time he wrote a very successful textbook onmechanics. In 1867 he became a professor at the Technical College inDelft.

He became director of theLeiden Observatory in 1872 upon the death of Frederik Kaiser. He retired in 1908.[1] Van de Sande Bakhuyzen became member of theRoyal Netherlands Academy of Arts and Sciences in 1872.[2]
He chose to concentrate on fundamental astronomy rather than on the then-new field ofspectroscopy. He worked mainly on the observation ofasteroids, but also proved the connection between ameteor shower on November 27 and thecomet3D/Biela. He also worked ongeodesy.
He edited and published the Mars drawings ofJohann Hieronymus Schröter in 1881, long after the latter's death.
He married Geertruida van Vollenhoven, who died in 1910. They had two daughters and a son, Adriaan, who would be mayor of Leiden from 1927 to 1941.
His brotherErnest-Frederich van de Sande Bakhuyzen was also an astronomer who worked at the Leiden Observatory.

Bakhuysen crater (with an "s") onMars is named for him.[3]