Non-Periodic Phenomena in Variable Stars
                                                IAU Colloquium, Budapest, 1968


                ON THE RESEARCH PROGRAM CONCERNING ECLIPSING
              VARIABLES AT THE OBSERVATORIES NURNBERG AND IZMIR

                                 E. POHL
                     Nurnberg Observatory, Germany


  The observatory of Nurnberg in Germany was opened in 1930 and has had 
above all the task to promote the astronomical education of the public. 
Besides, an astronomical research program concerning eclipsing variables 
has been carried out. Since the summer of 1963 a photoelectric photometer 
constructed in the workshop of the observatory was used for this observation 
program. We use a photomultiplier 1P21 attached to a 34 cm Cassegrain reflector. 
Since the spring of 1967 the measurements were registered with a 
Siemens-compensograph.
  The observation program covers a large part of the eclipsing variables 
brighter than magnitude 10. The measurements are carried out by myself 
and some members of the Nurnberg Astronomical Amateur Association. 
Unfortunately, the observatory is situated in the area of the city of 
Nurnberg, so the background in the case of faint stars often amounts to 
30 per cent of the intensity of the star. The centre of the city is in 
the west, and during many clear nights we can only measure up to a 
zenith distance of 45 degrees in this direction.
  From 1963 to 1968 about 120 minima of 38 various eclipsing variables 
could be determined in Nurnberg photoelectrically. For some stars minima 
were derived every year. Some of these frequently observed objects shows 
large O-C's against the elements of the General Catalogue 1958 and also 
of the last edition of the Krakow Catalogue. The star TX UMa shows 
finally an O-C value of more than 1 hour, and SW Lac a deviation of even 
1 1/4 hours from the elements of the Krakow Catalogue. For TX UMa, SW Lac, 
V 477 Cyg and i Boo new elements were determined basing on our results and 
published in the Bulletins of Com. 27 of the IAU in the year 1967.
  During several travels, first to the University Observatory of Ankara 
and than to the University of Izmir 1966, a cooperation for this observation 
program was agreed upon with Turkish astronomers. A particularly friendly and 
close cooperation with the director of the University Observatory of Izmir, 
Prof. Kizilirmak, and his staff has been existing for three years. In the 
spring of 1966, Prof. Kizilirmak and I agreed upon the erection of a common 
instrument for the photometry of eclipsing variables. This 48 cm Cassegrain 
reflector is fitted out with a photoelectric equipment similar to that existing 
already in Nurnberg. The telescope and the electronic parts of the photometer, 
wich were all constructed in Western Germany, were shipped to Izmir and set 
up at the University Observatory of Izmir in October last year. The main 
observational program of this instrument, which is to be carried out by 
the astronomers of the University Observatory of Izmir and by myself, is the
regular control of a large number of eclipsing variables up to the 11th 
magnitude, in order to revise the periods. The University Observatory of 
Izmir is situated on a mountain, 650 m above sea-level, about 20 km away 
from the city. It was founded 1964/65 under the direction of Prof. Kizilirmak, 
and its enlargement is still in progress. The future observation program 
- of the observatories in Nurnberg and Izmir, which will be essentially 
broadened - will be carried out commonly, and all results will also be 
published together. During the last 4 years already visual results have been 
achieved at the University Observatory of Izmir according to the Argelander 
method. The minima derived so far by the Nurnberg and Izmir observatories 
have been published in the Astronomische Nachrichten.
  On the 30th April 1968 the first photoelectric measurements of i Boo and 
SV Cam could be made with our new 48 cm telescope in Izmir. In the last 
4 months about 40 minima were derived under the favourable climatic conditions 
in Izmir. Between the Nurnberg and Izmir minima there are no systematic 
time-differences in the dates. Till today, at both observatories we have 
obtained photoelectric minima for more than 60 different eclipsing binaries.
  We hope, we shall be able to make a valuable contribution to the old but 
not yet clarified problem of the period changes of eclipsing binaries.