COMMISSION 27 OF THE I. A. U.
             INFORMATION BULLETIN ON VARIABLE STARS
                            NUMBER 36

                                         Konkoly Observatory
                                         Budapest
                                         4 November 1963


                THE SECONDARY PERIOD OF DL HERCULIS


      This variable star of RR Lyrae type was investigated by
Zessewitch (Odessa Isv. 3,257, 1953) who found strong variations
in the light curve with a period of 49d.2. He obtained the elements:

      Max. hel = 2426959.212 + 0d.5916291. E

      Min. ampl. = 2426975 + 49d.235.n

      With the 24" telescope of the Konkoly Observatory 750 photoelectric 
observations have been obtained in blue and yellow. These
observations show that the length of the secondary period is essentially
shorter than the value given by Zessewitch. The new elements are:

      Max. hel = 2438208.4282 + 0d.59162786. E

      Min. ampl = 2438227 + 33d.6. n


                          [FIGURE 1]

      The figure shows the variations of the heights of the maxima
(above) and the phase variations of the maxima (below) in blue color.
As the variable has a close companion which was measured together
with the variable, the true amplitude of the variation of the maximum
brightness must be larger than shown in the figure.

      The observations will be continued in 1964.


                                                 B. SZEIDL
                                             Konkoly Observatory
                                                 Budapest