The Danish Four-Channel uvby Photometer

The Danish Four-Channel uvby Photometer was mounted at the Cassegrain focus of the Danish 0.5-metre telescope at La Silla Observatory in the late 1970s. A revolutionary photometer, it permitted simultaneous observations in all the filters of the Strömgren four colour system (u, v, b and y) — a four-colour medium-band photometric system.

The building of four-channel uvby photometers started in the late 1960s, notably at the Brorfelde Observatory, where the development of photoelectric instrumentation received a major impulse with Strömgren’s return to Denmark in 1967.

During the 1970s and 1980s uvby-Hβ photometry became a standard tool for quantitative analysis of stellar spectra.

The four-channel photometer used a filter-set acquired from Kitt Peak National Observatory with transmission curves fairly close to those used in the original uvby system. The edges of the passbands were defined by slots cutting the spectrum produced by the photometer grating at positions where the filters transmission was less than 8% of maximum. The photomultipliers were of type EMI 6256SA operated at an ambient temperature.

The newer Six-Channel Photometer for the Danish 0.5-metre telescope replaced the Four-Channel uvby Photometer in 1987. This fully automated six-channel Strömgren photometer was able to make simultaneous measurements of all uvbyβ indices with one instrument.

The Danish Four-Channel uvby Photometer

This table lists the global capabilities of the instrument. The authoritative technical specifications as offered for astronomical observations are available from the Science Operations page.

Location: Decommissioned
Telescope: Danish 0.5-metre telescope
Focus: Cassegrain
Type: Photometer
Wavelength coverage: 350–547 nm
Spatial resolution: ?
Spectral resolution: 6 arc-seconds
First light: Late 1970s
Science goal:
  • Star Photometry
Images taken with the instrument: N/A
Images of the instrument: Link
Press Releases with the instrument: N/A
  • ESO