Site selection for the 3.4m optical telescope of the Iranian National Observatory

The results of the site selection campaign conducted for the proposed 3.4 m optical telescope of the Iranian National Observatory are reported. During the first three years, among 33 nominated regions throughout the country, the potential regions were confined to four provinces, namely, Southern Khorasan located in the east, Kerman in the south-east and Qom and Esfahan in the central part, by examining long-term meteorological and geographical parameters. Over the following three years, after astro-climate considerations and short-term atmospheric seeing measurements using a differential image motion monitor (DIMM) technique were carried out, four candidate sites were selected among these regions. Simultaneous seeing measurements were carried out on the four candidate sites and, finally, Dinava located at the common border of the Esfahan and Qom provinces and Gargash in the Kashan region were selected as the most promising sites. Continuous seeing measurements over 23 months yielded a median value of about 1.0 " for both sites. The latitude and longitude of the Dinava site are 50,54 E and 34,09 N, respectively and it is situated at an altitude of about 3000 m and about 57 km due south from Qom. The latitude and longitude of the Gargash site are 51,19 E and 33,40 N, respectively and it is situated at an altitude of about 3600 m and about 37 km due south from Kashan. With two sites in hand, further comparative measurements of seeing and weather data continued at the two sites, which resulted in the selection of the Gargash site for the construction of the Iranian National Observatory.