  The nature of the strong absorption features in the white dwarf GD229 has
been a real mystery ever since it was found to be magnetic in 1974. All
attempts to explain the spectrum by line components of hydrogen failed. With
the first sets of newly calculated line data for HeI in a strong magnetic field
we could identify most of the absorption structures in the spectrum with
stationary line components in a range of magnetic fields between 300 and 700
MG. This is much lower than previously speculated and is comparable to the
highest fields found in hydrogen rich magnetic white dwarfs. The reason for the
large number of spectral features in GD229 is the extreme accumulation of
stationary components of transitions in He I in a narrow interval of field
strengths.
