Oxygen and nickel abundances derived in the past years. The grey bar is the presently discussed range of the solar Ni abundance. Red symbols mean disc-integrated spectrum, green symbols disc centre. Stars indicate theoretical models, squares the HM model. The round dot of Centeno08: in the work a sun-spot spectrum is used. The dashed lines are lines of constant EW for disc centre, solid for disc-integrated light. This figure is an updated version of the one shown by Ludwig et al. (2010). The big green-blue star represents the result of this investigation. The horizontal dotted line at A(Ni) = 6.23 represents values from Grevesse & Sauval (1998); the horizontal dot-dashed line at A(Ni) = 6.17 the value from Scott et al. (2009); the horizontal dot-dashed line at A(Ni) = 6.20 the value from Scott et al. (2015).