Tseraskii, Vitold Karlovich

Born Apr. 27 (May 9), 1849, in Slutsk, Minsk Oblast; died May 29, 1925. Soviet astronomer. Corresponding member of the St. Petersburg Academy of Sciences (1914).

Tseraskii graduated from Moscow University in 1871. In 1878 he began working as an observational astronomer at the astronomical observatory of Moscow University, and from 1890 to 1916 he was the observatory’s director. Beginning in 1889, he was also a professor at Moscow University.

Tseraskii was one of the pioneers of instrumental photometry and the founder of the Moscow school of photometry. He worked out the methodology of photometric observations and achieved what was then high accuracy in the determination of stellar brightness. In the period 1875–1903 he measured the brightness of more than 500 stars; he was one of the first to determine (1903) the stellar magnitude of the sun. In 1895, on the basis of experiments on the melting of metals at the focus of a concave mirror, Tseraskii first established the lower limit for the temperature of the sun as 3500°C.

In 1885, Tseraskii discovered the existence of noctilucent clouds, and, with A. A. Belopol’skii, he established that they are located high above the earth (about 80 km). In 1895 the systematic photography of the sky was begun at his initiative in order to detect and investigate variable stars from the photographs obtained.