Context : We perform a comprehensive spectral analysis of LS V +46 \degr 21 in order to compare its photospheric properties to theoretical predictions from stellar evolution theory as well as from diffusion calculations .

Aims : LS V +46 \degr 21 is the DAO-type central star of the planetary nebula Sh 2 - 216 .
High-resolution , high-S/N ultraviolet observations obtained with FUSE and STIS aboard the HST as well as the optical spectrum have been analyzed in order to determine the photospheric parameters and the spectroscopic distance .

Methods : We performed a detailed spectral analysis of the ultraviolet and optical spectrum by means of state-of-the-art NLTE model-atmosphere techniques .

Results : From the N IV – N V , O IV – O VI , Si IV – Si V , and Fe V – Fe VII ionization equilibria , we determined an effective temperature of ( 95 \pm 2 ) \mathrm { kK } with high precision .
The surface gravity is \log g \hskip { -1.422638 pt } = \hskip { -1.422638 pt } 6.9 \pm 0.2 .
An unexplained discrepancy appears between the spectroscopic distance d = 224 ^ { +46 } _ { -58 } \mathrm { pc } and the parallax distance d = 129 ^ { +6 } _ { -5 } \mathrm { pc } of LS V +46 \degr 21 .
For the first time , we have identified Mg IV and Ar VI absorption lines in the spectrum of a hydrogen-rich central star and determined the Mg and Ar abundances as well as the individual abundances of iron-group elements ( Cr , Mn , Fe , Co , and Ni ) .
With the realistic treatment of metal opacities up to the iron group in the model-atmosphere calculations , the so-called Balmer-line problem ( found in models that neglect metal-line blanketing ) vanishes .

Conclusions : Spectral analysis by means of NLTE model atmospheres has presently arrived at a high level of sophistication , which is now hampered largely by the lack of reliable atomic data and accurate line-broadening tables .
Strong efforts should be made to improve upon this situation .