COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS.
                      Number 1307

                                  Konkoly Observatory
                                  Budapest
                                  1977 July 21




    PHOTOELECTRIC OBSERVATIONS OF NOVA SAGITTARII 1977




    Photoelectric observations of Nova Sagittarii 1977
(alpha1950 =18h35m17s; delta1950= -23d 25'21") were secured on the 104-cm
and 56-cm reflectors of the Uttar Pradesh State Observatory on
several nights during April and May 1977, using UBV filters of
the Johnson and Morgan system and photomultipliers cooled to
-20dC. Standard dc techniques were employed for recording.
    The standard deviations of the comparison star (HD 171810=
SAO 187068) on any single night are +-0.017m; +-0.023m; +-0.022m in
the V, B and U filters respectively, for both the reflectors.
The magnitudes and the colours of the nova and the comparison
star are given in Table 1. The light and colour curves of the
nova are plotted in Fig. 1 and the colour-colour curve in Fig. 2.
    The comparison star happens to be the same as the one used
by Austin who has also observed the nova photoelectrically on
three nights earlier to our observations (IAU Circular No. 3067).
Small systematic differences between the standard magnitudes
and colours of the comparison star obtained by Austin and by us
are to be noted.
     From the V light curve, the average rate of decline of the
nova during the period of our observations comes out to be 0.04m
per day. The colour curves and the colour-colour diagram of the
nova indicate that, in an over all way, the nova relatively
brightened up in the B such that, apart from small fluctuations,
the B-V index got bluer at an average rate of 0.02 per 10 days,
and the U-B index got redder at an average rate of 0.04m per 10
days.

                     [FIGURE 1]

Fig. 1. Light and colour curves of Nova Sagittarii 1977

                     [FIGURE 2]

Fig. 2. Colour-colour diagram of Nova Sagittarii 1977. The
numbers represent the position of the nova in the
colour-colour diagram on successive nights of Table 1.


                      Table 1
Magnitude and colours of Nova Sagittarii 1977 and the comparison
star HD 171810 (= SAO 187068).

Sr    Date, U.T.   V       (B-V)   (U-B)      Number of
No.   1977                                    observations
 1 April 6.96d    9.59m     0.36m   -0.75m      2
 2      10.92     9.82      0.31    -0.80       2
 3      11.96     9.50      0.34    -0.77       5
 4      17.94     9.56      0.40    -0.85       7
 5*     20.90     9.66      0.31    -0.72       6
 6*     21.92    10.04      0.29    -0.76       4
 7*     24.94    10.22      0.33    -0.77       3
 8*     25.89     9.89      0.35    -0.67       8
 9   May 6.88    10.58      0.32    -0.68       6
10      11.93    11.02      0.29    -0.59       4
11      15.83    10.99      0.28    -0.71       9
12      17.85    11.02      0.24    -0.66       3
Comparison star   8.16      0.56     0.00
*Observed on 56-cm telescope.

Acknowledgement
    The authors are thankful to Dr.S.D. Sinvhal for helpful
discussions. Thanks are also due to C.D. Kandpal, A.K. Bhatnagar,
U.C. Joshi and B.B. Sanwal for participation in the observations.





                                      RAM SAGAR
                                      H.S. MAHRA
                                      S.C. JOSHI
                                      J.B. SRIVASTAVA
             
                                      Uttar Pradesh State
                                      Observatory, Manora Peak,
                                      Naini Tal-263129
                                      India