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.

Edwin Brant Frost II (July 16, 1866 – May 14, 1935) was an American astronomer.

He was born in Brattleboro, Vermont. His father, Carlton Pennington Frost, was dean of Dartmouth Medical School.

Frost graduated from Dartmouth in 1886. He continued his education as a post-graduate student in chemistry and in 1887 became an instructor in physics while only 21 years old. In 1890 Frost went abroad to Europe and ended up researching stellar spectroscopy under Hermann Vogel in Potsdam. He returned to Dartmouth in 1892 as an assistant professor of astronomy.

The Reverend Thomas Henry Espinell Compton Espin or T. H. E. C. Espin (28 May 1858 – 2 December 1934) was a British astronomer. His father Thomas Espin was Chancellor of the Diocese of Chester and his mother was Elizabeth (née Jessop).

He became interested in astronomy after the appearance of "Coggia's Comet" (C/1874 H1).

William Frederick Denning, FRAS (25 November 1848 – 9 June 1931) was a British astronomer who achieved considerable success without formal scientific training.

Denning devoted a great deal of time to searching for comets, and discovered several including the periodic comet 72P/Denning-Fujikawa and the lost comet D/1894 F1. The latter was the last comet discovered on British soil until the discoveries of George Alcock.