Eclipsing high-mass binaries I. Light curves and system parameters for CPD−51 ◦ 8946, PISMIS24-1 and

Received; accepted We present first results of a comprehensive photometric O-star survey performed with a robotic twin refractor at the Universitätssternwarte Bochum located near Cerro Armazones in Chile. For three high-mass stars, namely Pismis 24-1, CPD−51 ◦ 8946 and HD 319702, we determined the period through the Lafler-Kinman algorithm and model the light curves within the framework of the Roche geometry. For Pismis 24-1, a previously known eclipsing binary, we provide first light curves and de-termined a photometric period of 2.36 days together with an orbital inclination of 61.8◦. The best-fitting model solution to the light curves suggest a detached configuration. With a primary temperature of T1 = 42520 K we obtain the temperature of the secondary component as T2 = 41500 K. CPD − 51 ◦ 8946 is another known eclipsing binary for which we present a revised photometric period of 1.96 days with an orbital inclination of 58.4◦. The system has likely a semi-detached configuration and a mass ratio q = M1/M2 = 2.8. If we adopt a primary temperature of T1 = 34550 K we obtain T2 = 21500 K for the secondary component. HD 319702 is a newly discovered eclipsing binary member of the young open cluster NGC 6334. The system shows well-defined eclipses favouring a de-tached configuration with a period of 2.0 days and an orbital inclination of 67.5◦. Combining our photometric result with the primary spectral type O8 III(f) (T1 = 34000 K) we derive a temperature of T2 = 25200 K for the secondary component