A photometric system with five wavelength ranges that does not use
filters. Instead it uses prisms and lenses (spectroscopy) to select
the bands simultaneously. The wavelengths and the bandwidths are:
W, 3250 and 140 Å; U, 3630 and 240 Å;
L, 3840 and 230 Å; B, 4320 and 450 Å; and
V, 5470 and 720 Å. The Walraven photometer was unique in
design and remained literally unique as copies were never built. In
addition, during its whole life the photometer was mounted permanently
on the same telescope that had been built specifically for this
instrument, the 91 cm Lightcollector’ reflector, which started in 1958
at the Leiden Southern Station in Broederstroom, South-Africa. After
20 years in South-Africa the telescope and photometer were moved to
the European Southern Observatory La Silla observatory in Chile.
The photometric observations were resumed in March 1979 and continued
for another 12 years until the decommissioning of the photometer in 1991.
See also: After the inventors, the Dutch astronomer Theodore Walraven (1916-) and his wife
Johanna Helena Walraven, née Terlinden (1920-89); → photometry.
