Sir Frank Watson Dyson, KBE, FRS (8 January 1868 – 25 May 1939) was an English astronomer and Astronomer Royal who is remembered today largely for introducing time signals ("pips") from Greenwich, England, and for the role he played in testing Einstein's theory of general relativity.

Édouard Benjamin Baillaud (14 February 1848 – 8 July 1934) was a French astronomer.

Born in Chalon-sur-Saône, Baillaud studied at the École Normale Supérieure (1866-1869) and the University of Paris. He worked as an assistant at the Paris Observatory beginning in 1872. Later he was director of the Toulouse Observatory from 1878 to 1907, during much of this time serving as Dean of the University of Toulouse Faculty of Science.

Johan Oskar Backlund (April 28, 1846 – August 29, 1916) was a Swedish-Russian astronomer. His name is sometimes given as Jöns Oskar Backlund, however even contemporary Swedish sources give "Johan". In Russia, where he spent his entire career, he is known as Oskar Andreevich Baklund (Оскар Андреевич Баклунд). Russian sources sometimes give his dates of birth and death as April 16, 1846 and August 16, 1916, in the Julian calendar that was used in Russia during that period.

Alfred Wolfer, who died on 1931 October 8, was for fifty years associated with the Federal Observatory at Zürich. Throughout that time he worked specially on sunspots - a subject which had been taken up by his predecessor, Rudolf L. Wolf, the first director of the observatory. The activity of the observatory in discussing the frequency of sunspots from records back to 1610, and in collecting later data, led to it being chosen as the centre for sunspot data by the International Astronomical Union.

Edward Walter Maunder (12 April 1851 – 21 March 1928) was an English astronomer best remembered for his study of sunspots and the solar magnetic cycle that led to his identification of the period from 1645 to 1715 that is now known as the Maunder Minimum.

Maunder was born in London, the youngest child of a minister of the Wesleyan Society. He attended King's College London but never graduated. He took a job in a London bank to finance his studies.

Kiyotsugu Hirayama was born on October 13, 1874 at Sendai, which has been the largest city in the north-east district of Japan. He was educated there up to the age of 20. He studied foreign languages and basic science as well as classical Chinese which intellectual Japanese should have mastered. He left Sendai to enter the University of Tokyo in 1894. He succeeded in the entrance examination, majored astronomy and graduated it in 1897.