COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1871

                                  Konkoly Observatory
                                  Budapest
                                  1980 November 21

                                  HU ISSN 0374-0676



            THE ECLIPSE OF CI Cyg IN 1980



   The symbiotic star CI Cyg is known for recurrent deep fadings
of the visual luminosity going up to 2-3 magnitudes, which take
place with a period of about 855d (Pucinskas, 1972).
   In 1975 a deep minimum with the duration of about 100d was
observed and was interpreted as a regular eclipse of the hot component 
by the cold one (Belyakina, 1976 and 1979a).
   Another minimum was detected in 1977-78, but few photoelectric
observations were secured (Belyakina, 1979b).
   Photoelectric UBV observations of CI Cyg were planned using
the 50 cm reflector at the Collurania Astronomical Observatory in
the occurrence of the eclipse of 1980.
   Bad sky conditions during the period corresponding to the beginning 
of the minimum phase (at the end of April) have prevented 
us to observe. The observations were carried out during the
period June-October,
   BD +35d3824 and an anonymous star in the field of CI Cyg
were respectively used as comparison and check stars; BD+35d3821
was also observed to obtain a comparison with the observations by
Belyakina. The results of these observations are plotted in Fig.1.
   The mean variations in U, B and V colours are 1.30m, 0.90m
and 0.50m, respectively.
   It is interesting to note that the U, B and V lightcurves
are not synchronous, in particular the eclipse in the U colour
seems to last more than in B and V colours.
   Small fluctuations are seen over the curves of Fig. 1;
their amplitudes are close to 0.2-0.3mag. with a duration of some
days.

                       [FIGURE 1]


   A detailed analysis of the lightcurves of CI Cyg will be
presented in a forthcoming paper.






         R. BURCHI, A. Di PAOLANTONIO, S. MANCUSO,
              L. MILANO and A. VITTONE

         Collurania Astronomical Observatory
         Capodimonte Astronomical Observatory
         via Moiariello, 16, I-80131 Napoli, Italy



References:
Belyakina, T.S.: 1976, I.B.V.S. No. 1169
Belyakina, T.S.: 1979a, Izv. Krimsk. Astrophys. Obs. 59
Belyakina, T.S.: 1979b, I.B.V.S. No. 1602
Pucinskas, A.: 1972, Bull. Vilnius Obs. 33, 55 [BIBCODE 1972VilOB..33...50P ]