2. The observations

To carry out our programe we performed 18 observing campaings, between March 1990 and May 1996 at three different observatories. A large fraction of the data were collected at The Calar Alto Observatory (Almeria, Spain). The telescope used was the 1.5 m reflector equipped with either a multipurpose one-channel photoelectric photometer or, alternately, with a four-channel spectrograph photometer, both using narrow and wide filters. Two photometric campaigns were carried out at The European Southern Observatory (La Silla, Chile) using the 0.5 m Danish telescope equipped with a four-channel photometer, with Strömgren uvby filters as well as Crawford's narrow and wide filters, identical to the one used at Calar Alto. Finally one complementary campaign was performed at the Sierra Nevada Observatory (Granada, Spain) using the 1 m telescope with the same one-channel photoelectric photometer used at Calar Alto.

The 294 measurements of ZZ UMa were obtained in the Strömgren uvby system during eight of the observing campaigns, using the 1.5 m telescope of the Observatorio Astronómico Nacional at The Calar Alto Observatory at Almeria, Spain, except for the seventh campaign that was carried out using the 1 m telescope of the Instituto de Astrofísica de Andalucía at the Sierra Nevada Observatory, Granada, Spain.

1. Six nights in March 1990 using the mono-channel photometer, (MO), mounted on the 1.5 m telescope.
2. One night in January 1991 with the same MO photometer.
3. Six nights in January 1992 using the four-channel photometer, (MU).
4. Two nights in January 1993 with the MU photometer.
5. Three nights in April 1994 using the MO photometer.
6. Three nights in June 1995 using the MO photometer.
7. Three nights in December 1995 using the same multi-channel photometer, MU, mounted on the 1 m telescope at Sierra Nevada.
8. One night in May 1996 with the MO photometer.

Details about the instrumental configuration for each telescope used can be found in Lahulla & Pensado (1981), Grønbech et al. (1976) and Nielsen (1983).

Average standard magnitudes and colour indices for ZZ UMa and the comparison stars are given in Table 1 (click here). See next section.

  
Figure 1: ZZ UMa differential light curve. y filter