COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                       Number 1058

                                 Konkoly Observatory
                                 Budapest
                                 1975 November 5



        SHORT PERIOD VARIABILITY OF NOVA CYGNI 1975




   Short period variability of Nova Cygni 1975 was reported by
Tempesti (1975a,b) and Koch and Ambruster (1975a,b).
   Nova Cygni was monitored photoelectrically for about 3 hours
in B and V on September 8 and for about 6 hours in V on September 
18, 1975. The observations were carried out with the aid of
the 60 cm reflector of the Ostrowik station of the Warsaw University 
Observatory. The star BD +47d3322 was used as the comparison
on the first date and BD +47d3340 on the second date.
   The differences DeltaV and DeltaB (in instrumental system) between
the Nova and the corresponding comparison star are plotted in
Figure 1. Full dots in Figure 1 denote yellow observations,the
open circles correspond to blue observations. The amplitude of
light variations was about 0.16 mag. in blue and 0.14 mag. in
yellow on September 8 and 0.06 mag. in yellow on September 18.
   The times of minima determined on basis of the present 
observations are JD_Hel 2442664.302, 2442674.308 and 2442674.453 and
the times of maxima are 2442664.359 and 2442674.359.
   Figure 2 shows O-C diagram obtained on basis of the present
times of minima and maxima and those given by Koch and Ambruster
(1975a,b). The times of minima in the Figure 2 are marked with
full dots, the times of maxima with open circles. The O-C residuals 
were calculated with the preliminary ephemeris Min =
= 2442664.302 + 0.1410E, Max = 2442664.359 + 0.1410E.
   The O-C diagram seems to indicate change of period.
   Thanks are due to Miss J. Wolczyk for help in observations.



                          I. SEMENIUK

                     Warsaw University Observatory

References:
Koch, R.H., and Ambruster, C.W.  1975a, IAU Circ. 2837 [BIBCODE 1975IAUC.2837....2D ]
                     1975b, ibid., 2839 [BIBCODE 1975IAUC.2839....1H ]

Tempesti, P.  1975a, ibid., 2834 [BIBCODE 1975IAUC.2834....1K ]
              1975b, ibid., 2842 [BIBCODE 1975IAUC.2842....1G ]


                         [FIGURE 1]
                         [FIGURE 2]