Since 1973, four international campaigns were organized (1973, 1979, 1985, 1991). The 1985 campaign was better organized ; one obtained 160 photoelectrical light curves.
Our Astronomical Institute has participated in the 1990 - 1991 campaign by three telescopes operating in Bucharest, Cluj - Napoca and Timisoara. The telescope from Bucharest and Timisoara are placed in the town, while that from Cluj - Napoca is situated in a hilly zone out of the town. A succinct presentation of the instruments above mentioned is given in Table 1. The photomultipliers used in our observations are : EMI 9502B (Bucharest), EMI QB9558 (Cluj-Napoca), EMI 9862R (Timisoara).
At Bucharest the time scale was guaranteed by a quartz clock (Rodhe und Schwarz). At Cluj - Napoca and Timisoara, marine chronometers were used.
No comparisons stars were used. The magnitudes were not corrected by extinction. We used the ephemeris given by Arlot (Arlot, 1990). One obtained eight light curves which are shown in Figures 1 - 8. In Tables 2 - 6 are given the observation data (time and relative magnitudes). For each light curve the minimum time was calculated by the Kwee and Van Woerden method (Kwee, Woerden, 1956).
The moments of the minimum and the dispersions are as follows :
- 1990.11.13 : 
, 
(Bucharest
Observatory)
- 1991.01.05 : 
, 
(Bucharest
Observatory)
- 1991.03.02 : 
(Cluj-Napoca Observatory)
- 1991.06.16 : 
(Cluj-Napoca Observatory)
- 1990.12.25 : 
, 
(Timisoara
Observatory)
- 1991.03.25 : 
, 
(Timisoara
Observatory)
- 1991.04.10 : 
, 
(Timisoara
Observatory)
- 1991.04.21 : 
, 
(Timisoara Observatory).
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Acknowledgement. The authors wish to express their thanks to Dr. J.E. Arlot for this help with sending all technical notes concerning the PHEMU-91 campaign.
Table 1: Presentation of the instruments
Table 2: Observational data at Bucharest Observatory
Table 3: Observational data at Cluj-Napoca Observatory
Table 4: Observational data at Timisoara Observatory
\
Table 5: Observational data at Timisoara Observatry
\
Table 6: Observational data at Timisoara Observatory