Separation of dwarf and giant stars with ROTSE-IIId

136 stars which were known to be the members of open cluster NGC 752 were observed at R band with ROTSE-IIId telescope located at the Turkish National Observatory (TUG) site. The data had been evaluated together with BV and 2MASS photometric data. A new practical method for separating dwarf and giant was described and applied. Evaluating the colour magnitude--diagrams with Padova isochrones revealed metallicity similar to the Sun and an age of 1.41 Gyr for the open cluster NGC 752.