COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1567

                                 Konkoly Observatory
                                 Budapest
                                 1979 March 12




       PHOTOELECTRIC OBSERVATIONS OF NOVA CYGNI 1978


Between Oct. 15 and Oct. 22, 1978, Nova Cygni 1978 was observed with the 1 m-
telescope of the Florence and George Wise Observatory of Tel Aviv University,
Israel. Photometric measurements were obtained with a two-channel photoelectric
photometer equipped with UBV-filters, monitoring simultaneously in one channel
the nova, and in the other a comparison star. They were reduced to the UBV-
system by means of some UBV standard stars given by Landold (Astr. J. 78, 959)
which were observed several times each night. Thus it was secured that possible
errors in the adopted brightness of the comparison star had no effect on the
measured brightness of the nova.
In Table 1 the results of the observations are compiled. For each night the mean
brightness and colours from all individual measurements as well as their mean
errors and the number of observations per colour are given. A single measurement
lasted 30 seconds in each colour except for Oct. 15 when the integration time was
5 seconds.
The brightness measured on Oct. 20 (given in brackets) is probably influenced
by clouds. The colours, however, seem to be reliable.
The position of the nova in a two - colour - diagram has been plotted and it is found
to move from the vicinity of the blackbody sequence towards the supergiant sequence.
The mean temperature during the observed period is near 11 000 K. But as long as
nothing certain is known about the interstellar reddening of the nova, this can
be regarded as a preliminary value only. There is a trend for the temperature to
increase with time, which is consistent with observations of other novae after
maximum.


--------------------------------------------------------------------
    Date (U.T.)         V               B-V            U-B        N
--------------------------------------------------------------------
1978 Oct.15.752     9.70+- 0.01     0.09+- 0.01   -0.83+- 0.01    17
         16.703     9.81   0.02     0.09   0.01   -0.55   0.02    5
         17.698     9.70   0.02     0.04   0.01   -0.75   0.01    4
         18.694     9.81   0.02     0.04   0.01   -0.70   0.01    4
         19.639     9.71   0.01     0.05   0.01   -0.73   0.01    4
         20.699   (10.49   0.02)    0.06   0.01   -0.72   0.02    4
         21.720     9.91   0.02     0.06   0.08   -0.74   0.03    4
         22.936     9.80   0.03    -0.02   0.02   -0.71   0.01    4
--------------------------------------------------------------------




Acknowledgement. The author thanks the Wise Observatory of Tel Aviv University
and the Smithsonian Research Foundation (Grant SFC-0-3005) for the opportunity
to use their facilities at Mitzpe Ramon, Israel.





                       A. BRUCH
                       Astronomisches Institut
                       der Universitat Munster
                       Steinfurter Str. 107
                       4400 Munster
                       F.R.G.