routines developed by Bergeron et al. ([@besa92]) and Saffer et al. ([@sabe94]), as modified by Napiwotzki et al. ([@nagr99]), which employ a $\chi^2$ test. The $\sigma$ necessary for the calculation of $\chi^2$ is estimated from the noise in the continuum regions of the spectra. The fit program normalizes model spectra [*and*]{} observed spectra using the same points for the continuum definition. During the analysis of the data presented here we realized that helium-poor and helium-rich spectra required different sets of continuum points. Especially the use of the continuum points derived from helium-poor spectra for the analysis of helium-rich spectra can introduce large systematic errors, esp. overestimates of the helium abundance due to continuum points in the wings of strong helium lines and/or too narrow fitting windows for helium lines. We therefore refined the definition of the continuum points to correct for such errors. Using this new definition of the continuum points, we re-analysed the data for the blue hook stars in $\omega$ Centauri presented in Moehler et al. ([@mosw02]). The new results differ from the old ones usually within the mutual error bars, except for the two most helium-rich stars, as expected.

We used the Balmer lines H$_\beta$ to H$_{8}$ 