20th-century Dutch astronomers

Albertus (Albert) Antonie Nijland (30 October 1868 – 18 August 1936) was a Dutch astronomer. He was professor of astronomy at the Rijksuniversiteit Utrecht, and served as director of the Sterrewacht Sonnenborgh (now the Sterrekundig Instituut) of the university.
Nijland was born in Utrecht. In 1901 he participated in a Dutch solar eclipse expedition to Karang Sago, Sumatra.
He was noted for his observations of variable stars, and published a number of papers on the subject in Astronomische Nachrichten, and elsewhere, from 1917 until 1936. He proposed naming variable stars in each constellation using a simple numbering system beginning with V1, V2, ... and so forth. However the double-letter system starting with RR was already in
widespread use. As a result, variable stars after QZ were numbered according to Nijland's system beginning with V335.
In 1923 Nijland became member of the Royal Netherlands Academy of Arts and Sciences.The crater Nijland on the Moon is named after him.

Marcel Gilles Jozef Minnaert (12 February 1893 – 26 October 1970) was a Belgian-Dutch astronomer. He was born in Bruges and died in Utrecht. He is notable for his contributions to astronomy and physics and for a popular book on meteorological optics: Light and colour in the open air, first published in English in 1940.

Chriet Titulaer (May 9, 1943 – April 23, 2017), born in Hout-Blerick, Venlo, Limburg, was a Dutch astronomer, television presenter and popular science and technology writer. He lived in Houten, Utrecht.

Bartholomeus Jan "Bart" Bok (April 28, 1906 – August 5, 1983) was a Dutch-American astronomer, teacher, and lecturer. He is best known for his work on the structure and evolution of the Milky Way galaxy, and for the discovery of Bok globules, which are small, densely dark clouds of interstellar gas and dust that can be seen silhouetted against brighter backgrounds. Bok suggested that these globules may be in the process of contracting, before forming into stars.
Bok married fellow astronomer Priscilla Fairfield in 1929, and for the remainder of their lives, the two collaborated so closely on their astronomical work that the Royal Astronomical Society said "from that point on it is difficult and pointless to separate his achievements from hers". The Boks displayed such great mutual enthusiasm for explaining astronomy to the public that The Boston Globe described them in 1936 as "salesmen of the Milky Way".: 44  They worked together on research and co-authored academic papers, and their general interest book The Milky Way went through five editions and was "widely acclaimed as one of the most successful astronomical books ever published".Bok's primary research interest was the structure of our galaxy. When he was asked by the editors of Who's Who in America to submit a statement concerning "Thoughts on My Life", he wrote, "I have been a happy astronomer for the past sixty years, wandering through the highways and byways of our beautiful Milky Way."Bart Bok was an exceedingly popular personality in the field of astronomy, noted for his affability and humor. When asteroid 1983 Bok was named for him and his wife Priscilla, he thanked the International Astronomical Union for giving him "a little plot of land that I can retire to and live on."