We show that the open cluster Trumpler 20 , contrary to the earlier findings , is actually an old Galactic open cluster .
New CCD photometry and high-resolution spectroscopy are used to derive the main parameters of this cluster .
At [ Fe/H ] = - 0.11 for a single red giant star , the metallicity is slightly subsolar .
The best fit to the color-magnitude diagrams is achieved using a 1.3 Gyr isochrone with convective overshoot .
The cluster appears to have a significant reddening at E ( B-V ) =0.46 ( for B0 spectral type ) , although for red giants this high reddening yields the color temperature exceeding the spectroscopic T _ { eff } by about 200 K. Trumpler 20 is a very rich open cluster , containing at least 700 members brighter than M _ { V } = +4 .
It may extend over the field-of-view available in our study at 20 \hbox { $ { } ^ { \prime } $ } \times 20 ^ { \prime } .