  We investigate and compare experimental and numerical excitonic spectra of
the yellow series in cuprous oxide Cu$_2$O in the Voigt configuration and thus
partially extend the results from Schweiner et al. [Phys. Rev. B 95, 035202
(2017)], who only considered the Faraday configuration. The main difference
between the configurations is given by an additional effective electric field
in the Voigt configuration, caused by the motion of the exciton through the
magnetic field. This Magneto-Stark effect was already postulated by Gross et
al. and Thomas et al. in 1961 [Sov. Phys. Solid State 3, 221 (1961); Phys. Rev.
124, 657 (1961)]. Group theoretical considerations show that the field most of
all significantly increases the number of allowed lines by decreasing the
symmetry of the system. This conclusion is supported by both the experimental
and numerical data.

Materials Science;Mesoscale and Nanoscale Physics;Quantum Physics