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2 Observations of minimum light

In order to enlarge the number of times of minimum light, new observations for both systems were carried out. Our new photoelectric photometry was performed at four observatories with the aim of securing several well-covered primary and secondary minima for each variable:

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Ondrejov Observatory, Czech Republic: 65 cm reflecting telescope with CCD camera SBIG ST-8 and Cousins Rfilter;

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South Africa Astronomical Obsevatory (SAAO), Sutherland, South Africa: 50 cm Cassegrain telescope with Johnsons UBV filters and classical photometer;

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R. Szafraniec Observatory, Metzerlen, Switzerland: 35 cm Schmidt-Cassegrain telescope with photoelectric photometer STARLIGHT-1 and Johnsons B filter or CCD camera SBIG ST-6;

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private observatory of K.H. at Lelekovice, Czech Republic: 35 cm Newtonian telescope with CCD camera SBIG ST-6V and R filter.

The CCD measurements in Ondrejov and Lelekovice were done using the standard Cousins R filter. Flat fields for the reduction of the CCD frames were routinely obtained from exposures of regions of the sky taken at dusk or dawn. Several comparison stars were chosen in the same frame as the variables. During the observations, no variations in the brightness of these stars exceeding the possible error of measurements (typically $\sigma \simeq$ 0.005 mag) were detected. No correction was allowed for differential extinction, due to the proximity of the comparison stars to the variable and the resulting negligible differences in the air mass.

Photoelectric observations at SAAO were obtained with the modular photometer utilizing a Hamamatsu GaAs R943-02 photomultiplier during two weeks in August 1999. Each observation of an eclipsing binary was accompanied by observation of a local comparison star. The photoelectric measurements were done in the UBV filters of the Johnson photometric system with 10 s integration time. All observations were reduced to the Cousins E-region standard system (Menzies et al. 1989).

The new times of primary and secondary minimum and their errors were determined using the least squares fit of the data, by the bisecting cord method or the Kwee-van Woerden algorithm. Only the lower part of the eclipse was used. These times of minimum are presented in Table 1. Some of the published moments were newly determined using only the lower part of its observed light curve.


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