  We present results of our study of the long-period eclipsing binary star NN
Delphini (hereafter NN Del). The results are based on spectral data obtained
with the HRS echelle spectrograph of the Southern African Large Telescope
(SALT). Our constructed velocity curve is based on 19 spectra obtained between
2017 and 2019 years and covers all phases of the binary's orbit. The orbital
period, P=99.252 days, was determined from our spectral data and coincides with
the period determined in previous studies, as well as the system eccentricity
of $e=0.517$. Calculated velocity amplitudes of both components allow us to
determine the masses of both system components M_1 = 1.320 M_sun and M_2 =
1.433 M_sun with the accuracy about of one percent (0.8% and 1.1%),
respectively. Luminosities of both components are presented as L_1 = 4.164
L_sun and L_2 = 6.221 L_sun, and the effective temperatures of both components
were directly evaluated (T_eff = 6545~K and T_eff = 6190~K) together with the
metallicity of the system [Fe/H] = -0.19 dex and its color excess
E(B-V)=0.026~mag. Comparison with evolutionary tracks shows that the system age
is 2.25+/-0.19 Gyr, and both components are on the main sequence and have not
yet passed the turn point. Spectral type is F5V for the hotter component and
F8V for another one.
