H_β Photometer at the Danish 1.54-m

The H_β Photometer was mounted on the instrument adaptor at the Cassegrain focus of the Danish 1.54-metre telescope in 1979. This two-channel photometer allowed simultaneous measurements of the H_β line through a narrow (λ_HβN = 486.4 nm) and a wide filter (λ_HβW = 487 nm). By using a neutral-density filter it was also possible to measure bright standard stars fainter than V=4.0 (without the neutral-density filter) or V=1.0 (with the neutral-density filter).

Six diaphragms with different diameters (100, 30, 20, 10, 7 and 4 arcseconds) were available on a wheel that could be rotated by pushing a button on an auxiliary instrument control rack. The data output was saved on paper tape in ASCII.

The H_β Photometer was decommissioned in the 1980s.