also due to variations in the atmospheric helium abundance along the blue tail in NGC 2808.

Atmospheric parameters
----------------------

  -------- ---------- ---------------------- -------------------- ----------------------------------------
  Star     $\chi^2$     [$ {\rm T_{eff}}$]{}   [$\log {\rm g}$]{}   [${\rm \log{\frac{n_{He}}{n_{H}}}}$]{}
                                       \[K\]                      
  W6022    2.23               30300$\pm$ 480        5.57$\pm$0.05                         $-$1.99$\pm$0.07
  W6816    2.39               21300$\pm$ 540        4.88$\pm$0.07                         $-$2.17$\pm$0.05
  W6849    1.88               37500$\pm$ 330        5.77$\pm$0.09                         $-$0.82$\pm$0.05
  W7084    1.63               35300$\pm$ 580        5.91$\pm$0.10                         $-$0.57$\pm$0.05
  W8750    2.52               48000$\pm$1300        6.21$\pm$0.14                         $-$1.78$\pm$0.15
  W9301    2.14               21100$\pm$ 560        4.92$\pm$0.07                         $-$2.05$\pm$0.05
  W9855    2.45               35700$\pm$ 580        5.60$\pm$0.12                         $-$0.74$\pm$0.05
  W9863    2.04               53000$\pm$2100        5.81$\pm$0.10                         $-$1.56$\pm$0.14
  W14040   2.16               40400$\pm$ 220        5.63$\pm$0.05                         $-$0.31$\pm$0.03
  W14711   2.92               20100$\pm$ 520        4.87$\pm$0.07                         $-$1.93$\pm$0.05
  W18803   1.70               35700$\pm$ 510        5.96$\pm$0.09                         $-$0.38$\pm$0.03
  W18899   1.91               35500$\pm$ 790        5.70$\pm$0.12                         $-$0.21$\pm$0.05
  W20334   2.15               36300$\pm$ 900        5.79$\pm$0.15                         $+$1.02$\pm$0.02
  W21882   4.09               67000$\pm$1500        6.99$\pm$0.09                         $-$2.91$\pm$0.12
  W23198   2.38               34600$\pm$ 400        5.81$\pm$0.07                         $-$1.22$\pm$0.05
  W25794   1.44               36600$\pm$ 460        5.67$\pm$0.09                         $-$0.65$\pm$0.03
  W26182   1.79               24200$\pm$ 640        5.22$\pm$0.07                         $-$2.37$\pm$0.05
  W26607   2.91               36300$\pm$ 520        5.63$\pm$0.09                         $-$0.36$\pm$0.03
  W27412   2.64               28700$\pm$ 640        5.37$\pm$0.07                         $-$2.77$\pm$0.12
  -------- ---------- ---------------------- -------------------- ----------------------------------------

  : Atmospheric parameters of the stars in NGC 2808\[tab-par\]

  --------- ---------- ---------------------- -------------------- ----------------------------------------
  Star      $\chi^2$     [$ {\rm T_{eff}}$]{}   [$\log {\rm g}$]{}   [${\rm \log{\frac{n_{He}}{n_{H}}}}$]{}
                                        \[K\]                      
  WF3-1     1.34               36000$\pm$2100        5.97$\pm$0.40                         $-$2.07$\pm$0.50
  BC6022    1.96               46000$\pm$1100        6.14$\pm$0.15                         $-$1.76$\pm$0.14
  BC8117    1.65               30000$\pm$1600        5.43$\pm$0.21                         $-$2.33$\pm$0.26
  BC21840   2.94               36000$\pm$1000        5.44$\pm$0.19                         $-$0.78$\pm$0.12
  C521      2.20               35000$\pm$ 620        