Lithium in a metal-poor Halo Star

This image shows a spectrum of the metal-poor star G271-162 in the red spectral region around the Li-line at 671 nm that is used to derive the lithium isotopic ratio. The wavelengths of the doublet components of the two isotopes are indicated. The total exposure time was 3 hours and the S/N-ratio in the continuum region is above 600 - a most satisfactory result considering that the CCD fringing amplitude is more than 20% at these wavelengths.