We study the effects of the Point Spread Function (PSF) on the performance
of the Objective Crystal Spectrometer (OCS) of the SODART telescope. The ad
vantage of OCS/SODART over XMM and AXAF instruments in studying of the diff
use sources is illustrated by modelling of the OCS/SODART observation of Ty
cho and Cas A Supernova Remnants (SNR).