Two-Channel Photometer at the Danish 1.54-m
The Two-Channel Photometer was mounted on the instrument adaptor at the Cassegrain focus of the Danish 1.54-metre telescope in 1979. It could be used as a one-channel photometer or as a two-channel photometer for simultaneous observation of an object and the background.
The photometer was divided into two sections: a basic one containing a diaphragm wheel and a filter wheel, and an exchangeable one for use with photomultipliers. The two main photomultipliers were called “Blue Detector Section” and “Red Detector Section”.
The diaphragm wheel contained five pairs of holes with diameters of 110, 31, 16, 9, 7 and 4 arcseconds and one large hole for field viewing centred on the optical axis. The filter wheel had space for up to 10 filters with maximum thickness of 10 mm.
A neutral-density filter was also available, mainly in cases where the brightness of the source was not well known and the user could not risk exceeding the maximum count rate allowed by the detectors.
Among the many observations performed by this photometer was the study of the dwarf cepheids E39 and NJL 220 in Omega Centauri in 1982.
The Two-Channel Photometer was decommissioned in the 1980s.
This table lists the global capabilities of the instrument.