Best-fit XTGRID with WD model to the Gemini/GMOS spectrum of J2102-4145 at orbital phase ϕ = 0.75 (maximum radial velocity difference) in the rest frame of the secondary. The observed spectrum can be reproduced by two nearly identical WD components (red and blue lines). The phase-resolved spectral coverage for the entire orbit is available in Figure A.2. The wavelength gap between ∼520–625 nm is due to the bad amplifier number 5 (see Section 2.2). The flux of the observation was adjusted to the flux level of the theoretical composite continuum.