Three colour photometry of galactic clusters NGC 2422, NGC 2423 and NGC 2437

The work is described in two parts:Part I contains a discussion of the work on the interpretation of the Hertzsprung-Russell diagram with regard to problems of stellar evolution .Part II describes the three-colour studies of the southern galactic clusters NGC 2422, NGC 2423, and NGC 2437. The colour excesses and distances, corrected for absorption, are: NGC 2422, 0.06 and 480 parsecs; NGC 2423, 0 and 450 parsecs; NGC 2437, 0.16, 1450 parsecs