10.4 De Sitter and Leiden
221
Fig. 10.11 Willem de Sitter. The instrument at the telescope is a Zöllner photometer (see
Sect. 2.3 and Fig. 2.6). This picture comes from the Album Amicorum, presented to H.G.
van de Sande Bakhuyzen on the occasion of his retirement as professor of astronomy
and director of the Sterrewacht Leiden in 1908 [47]
In Leiden the younger brother Ernst van de Sande Bakhuyzen was—as
he already was in Kapteyn’s Leiden days—still employed as an observator (see
Fig. 10.10). For a while it seemed that de Sitter (Fig. 10.11) would be appointed
as professor of astronomy as well as director of the Sterrewacht, a task that he,
as a more theoretically oriented person, must have felt to be rather challenging. Eventually, however, de Sitter was appointed professor and Ernst van de
Sande Bakhuyzen director of the Sterrewacht and extraordinary professor. The
older brother Hendricus could not be denied some conservatism; the younger
brother Ernst, however, was conservatism in the extreme. The story goes that
he asked and got permission to continue using petroleum lamps, because he
could not get used to electric light. De Sitter did not have his office at the