Two-Channel H_β Photometer at the Danish 0.5-m

The Two-Channel Hβ Photometer was mounted at the Cassegrain focus of the Danish 0.5-metre telescope at La Silla Observatory in the late 1970s. The two channels allowed simultaneous measurements of the Hβ line through narrow (HβN) and wide (HβW) filters and the light was collected by two photomultipliers. The two channels of the photometer also even made it possible to observe through clouds on moonless nights.