  Observations of the Earthshine off the Moon allow for the unique opportunity
to measure the large-scale Earth atmosphere. Another opportunity is realized
during a total lunar eclipse which, if seen from the Moon, is like a transit of
the Earth in front of the Sun. We thus aim at transmission spectroscopy of an
Earth transit by tracing the solar spectrum during the total lunar eclipse of
January 21, 2019. Time series spectra of the Tycho crater were taken with the
Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large
Binocular Telescope (LBT) in its polarimetric mode in Stokes IQUV at a spectral
resolution of 130000 (0.06 \AA). In particular, the spectra cover the red parts
of the optical spectrum between 7419-9067 \AA . The spectrograph's exposure
meter was used to obtain a light curve of the lunar eclipse. The brightness of
the Moon dimmed by 10.75 mag during umbral eclipse. We found both branches of
the O$_2$ A-band almost completely saturated as well as a strong increase of
H$_2$O absorption during totality. The deep penumbral spectra show significant
excess absorption from the NaI 5890 \AA doublet, the CaII infrared triplet
around 8600 \AA, and the KI line at 7699 \AA in addition to several
hyper-fine-structure lines of MnI and even from BaII. The detections of the
latter two elements are likely due to an untypical solar center-to-limb effect
rather than Earth's atmosphere. The absorption in CaII and KI remained visible
throughout umbral eclipse. A small continuum polarization of the O$_2$ A-band
of 0.12\% during umbral eclipse was detected at 6.3$\sigma$. No line
polarization of the O$_2$ A-band, or any other spectral-line feature, is
detected outside nor inside eclipse. It places an upper limit of $\approx$0.2\%
on the degree of line polarization during transmission through Earth's
atmosphere and magnetosphere.
