Any of several large, corvine birds having lustrous, black plumage and a loud, harsh call, especially Corvus corax, of the New and Old Worlds (Dictionary.com).
O.E. hræfn, hrefn; hræfn, cognate with O.Norse hrafn, Dan. ravn, Du. raaf, Ger. Rabe "raven," ultimately from PIE root *ker- imitative of harsh sounds (source also of L. crepare "to creak, clatter," cornix "crow," corvus "raven;" Gk. korax "raven," korone "crow;" O.C.S. kruku "raven;" Lith. krauklys "crow," related to Pers. kalâq, as below.
Kalâq, ultimately from Proto-Iranian*karak-, from *kar- "raven's harsh sound;" cf. Pers. qâr, qârqâr "croak," cognate with L. corvus, Gk. korax "a raven," Skt. kâkah, E. raven, as above and → crow.
Fr.: photométrie de Walraven
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.
After the inventors, the Dutch astronomer Theodore Walraven (1916-) and his wife Johanna Helena Walraven, née Terlinden (1920-89); → photometry.