  High-quality stellar spectra are in great demand now - they are the most
important ingredient in the stellar population synthesis to study galaxies and
star clusters. Here we describe the procedures to increase the quality of flux
calibration of stellar spectra. We use examples of NIR intermediate-resolution
Echelle spectra collected with the Folded InfraRed Echellete (R~6500, Magellan
Baade) and high-resolution UV-optical spectra observed with UVES (R~80000, ESO
VLT). By using these procedures, we achieved the quality of the global
spectrophotometric calibration as good as 1-2%, which fulfills the requirements
for the quality of stellar spectra intended to be used in the stellar
population synthesis
