  We present high-speed long term photometric observations from 1992 to 1996
(UBVRI), as well as recently obtained (1997) spectrophotometric and high
resolution spectroscopic studies of the bright galactic supersoft X-ray source
RXJ0019.8+2156. Our photometry reveals a highly variable object. The shortest
observed quasi-periodic variations are humps with a period of approx 1.8h. The
timings of the main minimum are not exactly regular and occur on average around
phase phi=0.0. With our new data set we calculated an update of the orbital
period.
  Our simultaneous spectroscopic and spectrophotometric studies from 1997 give
an even more detailed insight: blue and red shifted satellite lines at HeII
4686 and at the strong Balmer lines, which are interpreted as high velocity
outflows, can clearly be detected. We also present for the first time an
analysis of this supersoft source by means of Doppler tomography. The lines of
HeII (4542,4686), H_a and H_b show no emission from an accretion disk. These
emission lines originate in regions within the binary system with very low
velocities. The spatial origin of the emitting material is not quite clear and
will be investigated in a follow-up paper.
