COMMISSION 27 OF THE I. A. U.
         	INFORMATION BULLETIN ON VARIABLE STARS
                   	    NUMBER 852

                              	     Konkoly Observatory
                             	     Budapest
                             	     1973 December 4


           ECLIPSE TIMINGS OF CATACLYSMIC VARIABLES



    The following heliocentric times of mid-eclipse of the cataclysmic 
variables Z Cha, U Gem, EX Hya, VZ Scl and RW Tri have been
obtained over the past few years from observations made at the
McDonald Observatory of the University of Texas and at the Sutherland
site of the South African Astronomical Observatory.

I) Z Cha      	  O - C 	 Z Cha     O - C 
  JD hel                         JD Hel
 2441000+                       2441000+

 660.5002	-.0002 		692.4605   -.0001
 660.5747 	-.0002 		693.3542   -.0004
 661.5435 	 .0001 		695.4400   -.0005
 691.4177 	 .0001 		784.3182    .0001
 691.4923 	 .0002 		987.5521    .0001
 691.5668 	 .0002 		991.5747   -.0002
 692.3858 	-.0003

  O - C values are with respect to the revised elements:
  Hel.Minimum Light = JD 2440264.6828 + 0.07449923d E
where we have used Mumford's epoch (Astrophys.J. 165, 369, 1971)
combined with our more recent observations. The minima during the
period 691-695 were omitted from consideration when deriving the
revised period as they occurred during an outburst of this dwarf
nova.

II) U Gem   	O - C 		 U Gem            O - C
   JD hel         		 JD hel
  2440000+       	        2440000+
 679.6662 	.0035 		1356.6862	.0046
 680.7279 	.0037  		1361.8161	.0042
 976.8680 	.0033 		1365.7083	.0045
1281.8543 	.0039 		1368.7153	.0041
1296.8915 	.0041 		1676.5322	.0047
1297.7760	.0040

O - C values are with respect to the elements given by Krzeminski
(Astrophys.J. 142, 1051, 1965).

III) EX Hya	O - C
     JD hel
2441844.2601	-.0004

O - C values with respect to Mumford's elements (Astrophys. J. Suppl.
Ser. 15, 1, 1967).

IV) VZ Scl Ton 120
       JD hel
      2441000+          O - C
      209.8175            -
      279.6700          .0000

These eclipse timings, together with the epoch given by Krzeminski
(IBVS No.160), give revised elements:
	Hel.Minimum Light = JD 2441209.8175 + 0.14462220d E

V) RW Tri                       RW Tri
   JD hel  	O - C 		JD hel 		O - C
  2440000+                     2440000+
 890.7570      -.0015         1515.8570         -.0020
 891.9154      -.0025         1221.8855         -.0025
 895.8580      -.0019

O - C values are taken with respect to the elements given by Walker
(Astrophys.J. 137, 485, 1963).





                         B. WARNER
                         Department of Astronomy,
                         University of Cape Town,
                         South Africa.