COMMISSION 27 OF THE I. A. U.
             INFORMATION BULLETIN ON VARIABLE STARS
                         Number 2392


						Konkoly Observatory
						Budapest
						26 August 1983

						HU ISSN 0374-0676

		ECLIPSE TIMINGS OF 31 CYGNI


  Photoelectric UBV observations of the 1982 total eclipse of
31 Cygni were obtained with the Hopkins-Phoenix Observatory 20-cm
telescope and Braeside Observatory 41-cm telescope. Differential
magnitudes, relative to 30 Cygni, were found by differencing the
reduced all-sky photometry of each star. Mean extinction and
transformation coefficients, appropriate for each instrument,
were used in the calculations.
  Following the suggestion of Herczeg (1956), the time t_50 when
50% of the secondary's light is transmitted (through the outer
atmosphere of the primary) provides a more accurate description
of immersion or emersion than conventional timings of the four
contact points. The duration of eclipse is the time interval
between ingress and egress t_50 times, the time of mid-eclipse,
t_mid' is the mean of ingress and egress t_50 times. Although t_50
is wavelength dependent, t_mid is assumed to be wavelength 
independent (see Stencel et al. (1983) for details). Results of


                         Table I
--------------------------------------------------------------
For 1982 Eclipse:        U Filter             B Filter
--------------------------------------------------------------
Ingress t_50         JD 2445222.30+-0.13   JD 2445222.89+-0.13
t_mid                JD 2445254.39+-0.13   JD 2445254.39+-0.13
Egress t_50          JD 2445286.48+-0.13   JD 2445285.89+-0.13
Duration of Eclipse          64.18+-0.18           63.00+-0.18
(days)

For 1962 Eclipse:
Ingress t_50         JD 2437653.78+-0.21   JD 2437654.28+-0.21
t_mid                JD 2437685.72+-0.21   JD 2437685.72+-0.21
Egress t_50          JD 2437717.66+-0.21   JD 2437717.16+-0.21
Duration of Eclipse          63.88+-0.30           62.88+-0.30
(days)
--------------------------------------------------------------

these calculations and of similar calculations for the 1962 total
eclipse using Copenhagen University Observatory data (Gyldenkerne
and Johansen 1970) are given in Table I, where Julian Dates 
include heliocentric time corrections. Timings for the V filter
are not derived because the scatter of data is significant 
compared to the depth of eclipse.
  The mean duration of eclipse is 64.03+-0.17 days in U and
62.94+-0.17 days in B. The mean period of 31 Cygni, over two
cycles, is 3784.34+-0.12 days.





PAUL C. SCHMIDTKE                 JEFFREY L. HOPKINS
Kitt Peak National Observatory   Hopkins-Phoenix Observatory
P.O. Box 26732                   7812 West Clayton Drive
Tucson, Arizona 85726 USA        Phoenix, Arizona 85033 USA



ROBERT E. FRIED          	 ROBERT E. STENCEL
Braeside Observatory       	 Code EZ-7
P.O. Box 906
Flagstaff, Arizona 86002 USA     NASA Headquarters
                                 Washington, DC 20546 USA





References:
Gyldenkerne, K., and Johansen, K.T. 1970, Astron. Astrophys.
  Suppl. Ser. 1, 29 [BIBCODE 1970A&AS....1..129G ]
Herczeg, T. 1956, Mitt. Sternw. Budapest, Nr. 41, 18 [BIBCODE 1956CoKon..41...18H ]
Stencel, R.E., Hopkins, J.L., Hagen, W.A., Fried, R.E., Schmidtke
  P.C., Kondo, Y., and Chapman, R.D. 1983, in preparation [BIBCODE 1984ApJ...281..751S ]