  Transit spectroscopy is one of the most commonly used methods to characterize
exoplanets atmospheres. From the ground, these observations are very
challenging due to the terrestrial atmosphere and its intrinsic variations, but
high-spectral resolution observations overcome this difficulty by resolving the
spectral lines and taking advantage of the different Doppler velocities of the
Earth, the host star and the exoplanet. We analyze the transmission spectrum
around the Na I doublet at 589 nm of the exoplanet WASP-69b, a hot Jupiter
orbiting a K-type star with a period of 3.868 days, and compare the analysis to
that of the well-know hot Jupiter HD 189733b. We also present the analysis of
the Rossiter-McLaughlin effect for WASP-69b. Two transits of WASP-69b were
observed with the HARPS-North spectrograph (R = 115 000) at the TNG telescope.
We perform a telluric contamination subtraction based on the comparison between
the observed spectra and a telluric water model. Then, the common steps of the
differential spectroscopy are followed to extract the transmission spectrum.
The method is tested with archival transit data of the extensively studied
exoplanet HD 189733b, obtained with the HARPS-South spectrograph at ESO 3.6m
telescope, and then applied to WASP-69b data. For HD 189733b, we spectrally
resolve the Na I doublet and measure line contrasts of $0.72\pm0.05\%$ (D2) and
$0.51\pm0.05\%$ (D1), and FWHMs of $0.64\pm0.04${\AA} (D2) and
$0.60\pm0.06${\AA} (D1), in agreement with previously published results. A net
blueshift of ${\sim}0.04${\AA} is measured. For WASP-69b only the contrast of
the D2 line is measured ($5.8\pm0.3\%$). Even if this corresponds to a
detection at the $5\sigma$-level of excess absorption of $0.5\pm0.1\%$ in a
passband of $1.5${\AA}, more transits are needed to fully characterize the
lines profiles and retrieve accurate atmospheric properties.
