COMMISSION 27 OF THE I.A.U.
                 INFORMATION BULLETIN ON VARIABLE STARS
                             Number 3208

                                                         Konkoly Observatory
                                                         Budapest
                                                         24 June 1988

                                                         HU ISSN 0374 - 0676


       OPTICAL BEHAVIOUR OF AT CANCRI IN THE SEASON 1988

In supplementing and completing the light curve of AT Cnc the cataclysmic
star was measured on 24 blue-sensitive plates (ORWO-ZU21+GG13+BG12) from
9 nights obtained with the 50/70/172 cm Schmidt camera of Sonneberg Observatory
covering the time interval between 13 February and 19 April 1988. The 
observations, which are linked to the sequence of comparison stars given in the
IBVS No. 2363 are listed in Table I.


                      Table I

J.D.hel.    m_B      J.D.hel.    m_B       J.D.hel.   m_B
244...               244...                244...

7205.579   12.28m    7239.414   15.11m    7263.428   12.53m
7205.598   12.20     7262.388   12.44     7263.451   12.48
7205.617   11.91     7262.407   12.33     7265.373   12.65
7206.540   12.28     7262.427   12.44     7265.396   12.66
7206.560   12.15     7262.449   12.12     7265.415   12.76
7207.497   12.21     7263.357   12.31     7265.437   12.41
7207.515   12.33     7263.379   12.54     7267.358   12.70
7207.533   12.33     7263.403   12.29     7271.345   15.37

   The long-term light curve of AT Cnc, which results from the mean brightness
values of each night and which is given in Figure 1 shows most of the 
observations in the high state. Only on 2 plates from 18 March and 19 April 1988
is the object in the low state.
   Reducing all observations of the high state to one common epoch by means
of the improved orbital elements given in the IBVS No. 2918 the orbital light
changes and the displaced minimum phase in the high state to the phase ~0.5
can be confirmed. The results mentioned are given in Figure 2, where the
magnitudes m_B are plotted against the phases.


                             [FIGURE 1]
                             [FIGURE 2]



W. GOTZ

Akademie de Wissenschaften
der DDR, Zentralinsitut fur
Astrophysik, Sternwarte Sonneberg