  We present FUSE observations of the HeII Lyman alpha forest in the redshift
range 2.3 < z < 2.7 towards HS1700+6416. Between October 2002 and February
2003, the brightness of the QSO increased by a factor 2. Therefore, with an
exposure time of 203 ks during orbital night, the quality of the resulting
spectrum is comparable to the HE2347-4342 data. This second line of sight with
a resolved HeII Lyman alpha forest reveals a similar variation of several
orders of magnitude of the column density ratio eta = N(HeII)/N(HI) and
confirms the results of previous studies. The well-known metal line spectrum of
HS1700+6416 permits to examine the influence of metal line absorption on the
HeII column densities.

Astrophysics