Wavelength calibration at moderately high resolution^*

Royal Observatory of Belgium, Ringlaan 3, B–1180 Brussel, Belgium

Corresponding author: Send offprint request to: J.-P. De Cuyper, Jean-Pierre.DeCuyper@oma.be

Received: 24 January 1997
Accepted: 11 July 1997

Abstract

Th–Ar lamps are commonly used as wavelength calibration units at moderately high spectral resolutions because of the richness of the Th spectrum in the visual. The inclusion of blended lines whose position is assumed to coincide with the laboratory wavelength of the principal component is shown to result in a calibration precision significantly worse than the intrinsic random noise limit. In order to avoid this degradation of the calibration, we present resolution–dependent Th–Ar wavelengths in the region 277 to for use at pixel–scales between and .