Solar Observations made at the Malatya Station with Danjon Astrolabe

Authors: ORHAN GÖLBAŞI, HÜSEYİN KILIÇ, FERNAND CHOLLET

Abstract: The first results of astrometric solar observations made at the Malatya Station with a modified version of the Paris Observatory astrolabe are presented. This campaign was conducted as part of a cooperation between Inonü University and the Paris Observatory. The astrolabe, exactly the same as the one at Santiago de Chile [1], uses two reflecting prisms instead of transparent prisms in order to be able to observe at two zenith distances of 30^o and 60^o. The time is supplied by a Global Positioning System (GPS) receiver. The measurements (Table 1, 2) made between 1993 and 1994, were used in obtaining the annual mean solar semi- diameters reduced to one astronomical unit. The annual mean solar semi-diameter from CERGA, Santiago, San Fernando and Malatya are given in Table 3. The over all average value of the mean solar semi-diameter was found to be $959\".46 \pm 0\".08$ which is in very good agreement with those obtained at Centre d'Etudes et de Recherches Géodynamiques et Astronomiques (CERGA) Observatory (Table 4). Present observations do not reveal any real change in the solar semi-diameter.

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