Spectrum of a typical cluster galaxy (object 2). The red line represents the 1D spectrum, where the source is extracted as an ellipse with typically 1″ × 1″ axes and then summed in the spatial direction. The grey line represents the level of dispersion in the global sky, while the black dashed vertical lines represent restframe wavelengths of the most important transitions. At skylines grey vertical lines are plotted, and the redshift is shown in the top right corner.