We present FUSE observations of the line of sight to WD 0439 + 466 ( LS V + 46 21 ) , the central star of the old planetary nebula Sh 2–216 .
The FUSE data shows absorption by many interstellar and stellar lines , in particular D i , H _ { 2 } ( J = 0 – 9 ) , HD J = 0 – 1 , and CO .
Many other stellar and ISM lines are detected in the STIS E140M HST spectra of this sightline , which we use to determine N ( H i ) .
We derive , for the neutral gas , D/H = ( 0.76 \pm~ { } ^ { 0.12 } _ { 0.11 } ) \times 10 ^ { -5 } , O/H = ( 0.89 \pm~ { } ^ { 0.15 } _ { 0.11 } ) \times 10 ^ { -4 } and N/H = ( 3.24 \pm~ { } ^ { 0.61 } _ { 0.55 } ) \times 10 ^ { -5 } .
We argue that most of the gas along this sightline is associated with the planetary nebula .
The low D/H ratio is likely the result of this gas being processed through the star ( astrated ) but not mixed with the ISM .
This would be the first time that the D/H ratio has been measured in predominantly astrated gas .
The O/H and N/H ratios derived here are lower than typical values measured in other planetary nebulae likely due to unaccounted for ionization corrections .