COMMISSIONS 27 AND 42 OF THE IAU
               INFORMATION BULLETIN ON VARIABLE STARS
                           Number 3963

                                                    Konkoly Observatory
                                                    Budapest
                                                    17 December 1993

                                                    HU ISSN 0374 - 0676


               CCD PHOTOMETRY OF V1500 CYGNI IN 1993



In a continuing program to monitor V 1500 Cygni (Nova Cygni 1975), thirty "V" CCD images
with an integration time of 300 seconds were obtained by J. R. Rohde, D. Pascu, and J. A.
DeYoung using the U.S. Naval Observatory 1.55-meter astrometric reflector at Flagstaff, Arizona.
The Caltech Mark IV 800x800 charge-coupled device camera, with a Space Telescope F569WV
wide "V" filter was used to make the observations. The comparison star used was C1 as defined
by (Kaluzny and Semeniuk, 1987).

Figure 1 shows the differential instrumental V magnitude versus phase light curve for September
14, 1993. Vertical bars are standard errors from DAOPHOT aperture photometry (Stetson, 1987),
while the horizontal bars indicate the length of each 300-second exposure. The mean magnitude
was 17.8m (+-0.1m) which is fainter by 0.07m from our 1989 photometry with the same system
(Schmidt, DeYoung, and Wagner, 1989). The maximum magnitude was 17.3m (+-0.1m) and the
minimum magnitude was 18.3m(+-0.1m). This is a drop of 0.36m magnitude in amplitude from our
1987 and 1989 observations. The general shape of the light curve is sinusoidal and shows no
evidence of the flickering observed previously near minimum. The following linear ephemerides
were used in the reductions:

         Max (HJD) = 2443369.7116 + 0.1396131 * E (1)
         Min (HJD) = 2443369.6490 + 0.1396131 * E (2)

The times of maximum and minimum were determined by the method of (Kwee and van
Woerden, 1956) with the results shown in Table I. No correction is required at this time in the
above ephemerides. The period continues to remain stable. A finder chart prepared from a 61-
inch V band image is given in Figure 2.

 Table I. The observed heliocentric times of maximum and minimum of V 1500 Cygni.


        HJD        Type   Cycle   (O-C)
---------------------------------------
      2449244.7770 Max.   42081  +0.0065d
      2449244.8434 Min.   42082  -0.0015d


                                 [FIGURE 1]

                                 [FIGURE 2]

   Figure 2.  A two arc minute per side "V" band finder chart for V1500 Cygni.


Thanks are due to Lowell Observatory for use of the 2:1 reimaging coronograph and to the staff
of the U.S. Naval Observatory Flagstaff Station for allowing time on the telescope and for
assistance during the observing run.



                     James A. DeYoung
                     U.S. Naval Observatory
                     3450 Massachusetts Avenue NW
                     Washington DC 20392-5420
                     dey @ herschel.usno.navy.mil


References:

Kaluzny, J., and Semeniuk, I., 1987, Acta Astron., 37, 349. [BIBCODE 1987AcA....37..349K ]
Kwee, K. K. and van Woerden, H., 1956, Bull. Astron. Netherlands, 12, 327. [BIBCODE 1956BAN....12..327K ]
Schmidt, R. E., DeYoung, J. A. and Wagner, B. C., 1989, Inf. Bull. on Var. Stars, No. 3402.
Stetson, P. B., 1987, Pub. Astron. Soc. Pacific, 99, 191. [BIBCODE 1987PASP...99..191S ]